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High Efficiency Electron Transfer Realized over NiS2/MoSe2 S-Scheme Heterojunction in Photocatalytic Hydrogen Evolution
Yang Liu, Xuqiang Hao, Haiqiang Hu, Zhiliang Jin
2021, 37(6): 2008030-0  doi: 10.3866/PKU.WHXB202008030
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摘要:
S-scheme heterojunction is a major breakthrough in the field of photocatalysis. In this study, NiS2 and MoSe2 were prepared by a typical solvothermal method, and compounded by an in situ growth method to construct an S-scheme heterojunction. The obtained composite showed excellent performance in photocatalytic hydrogen evolution; the hydrogen production rate was approximately 7 mmol·h-1·g-1, which was 2.05 times and 2.44 times those of pure NiS2 and MoSe2, respectively. Through a series of characterizations, it was found that NiS2 and MoSe2 coupling can enhance the light absorption intensity, which is vital for the light reaction system. The efficiency of electron-hole pair separation is also among the important factors restricting photocatalytic reactions. Compared with pure NiS2 and MoSe2, NiS2/MoSe2 exhibited a higher photocurrent density, lower cathode current, and lower electrochemical impedance, which proves that the NiS2/MoSe2 complex can effectively promote photogenerated electron transfer. Simultaneously, the lower emission intensity of fluorescence indicated effective inhibition of electron-hole recombination in the NiS2/MoSe2 complex, which is favorable for the photocatalytic hydrogen evolution reaction. Further, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that MoSe2 is an amorphous sample surrounded by the NiS2 nanomicrosphere, which greatly increased the contact area between the two, thus increasing the active site of the reaction. Secondly, as a photosensitizer, Eosin Y (EY) effectively enhanced the absorption of light by the catalyst in the photoreaction system. Meanwhile, during sensitization, electrons were provided to the catalyst, which effectively improved the photocatalytic reaction efficiency. The establishment of S-scheme heterojunctions contributed to improving the redox capacity of the reaction system and was the most important link in the photocatalytic hydrogen reduction of aquatic products. It was also the main reason for the improvement of the hydrogen evolution effect in this study. The locations of the conduction band and valence band of NiS2 and MoSe2 were determined by Mott-Schottky plots and photon energy curves, and further proved the establishment of the S-scheme heterojunction. This work provides a new reference for studying the S-scheme heterojunction to effectively improve the photocatalytic hydrogen production efficiency.
Carboxyl-Functionalized Graphene for Highly Efficient H2-Evolution Activity of TiO2 Photocatalyst
Ping Wang, Haitao Li, Yanjie Cao, Huogen Yu
2021, 37(6): 2008047-0  doi: 10.3866/PKU.WHXB202008047
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The use of semiconductor photocatalysts (CdS, g-C3N4, TiO2, etc.) to generate hydrogen (H2) is a prospective strategy that can convert solar energy into hydrogen energy, thereby meeting future energy demands. Among the numerous photocatalysts, TiO2 has attracted significant attention because of its suitable reduction potential and excellent chemical stability. However, the photoexcited electrons and holes of TiO2 are easily quenched, leading to limited photocatalytic performance. Furthermore, graphene has been used as an effective electron cocatalyst in the accelerated transport of photoinduced electrons to enhance the H2-production performance of TiO2, owing to its excellent conductivity and high charge carrier mobility. For an efficient graphene-based photocatalyst, the rapid transfer of photogenerated electrons is extremely important along with an effectual interfacial H2-production reaction on the graphene surface. Therefore, it is necessary to further optimize the graphene microstructures (functionalized graphene) to improve the H2-production performance of graphene-based TiO2 photocatalysts. The introduction of H2-evolution active sites onto the graphene surface is an effective strategy for the functionalization of graphene. Compared with the noncovalent functionalization of graphene (such as loading Pt, MoSx, and CoSx on the graphene surface), its covalent functionalization can provide a strong interaction between graphene and organic molecules in the form of H2-evolution active sites that are produced by chemical reactions. In this study, carboxyl-functionalized graphene (rGO-COOH) was successfully modified via ring-opening and esterification reactions on the TiO2 surface by using an ultrasound-assisted self-assembly method to prepare a high-activity TiO2/rGO-COOH photocatalyst. The Fourier transform infrared (FTIR) spectra, X-ray photoelectron spectroscopy (XPS), and thermogravimetric (TG) curves revealed the successful covalent functionalization of GO to rGO-COOH by significantly enhanced ―COOH groups in FTIR and increased peak area of carboxyl groups in XPS. A series of characterizations, including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), XPS, and UV-Vis adsorption spectra, were performed to demonstrate the successful synthesis of TiO2/rGO-COOH photocatalysts. The experimental data for the hydrogen-evolution rate showed that the TiO2/rGO-COOH displayed an extremely high hydrogen-generation activity (254.2 μmol∙h−1∙g−1), which was 2.06- and 4.48-fold higher than those of TiO2/GO and TiO2, respectively. The enhanced photocatalytic activity of TiO2/rGO-COOH is ascribed to the carboxyl groups of carboxyl-functionalized graphene, which act as effective hydrogen-generation active sites and enrich hydrogen ions owing to their excellent nucleophilicity that facilitates the interfacial hydrogen production reaction of TiO2. This study provides novel insights into the development of high-activity graphene-supported photocatalysts in the hydrogen-generation field.
Controllable Synthesis of g-C3N4 Inverse Opal Photocatalysts for Superior Hydrogen Evolution
Yiwen Chen, Lingling Li, Quanlong Xu, Düren Tina, Jiajie Fan, Dekun Ma
2021, 37(6): 2009080-0  doi: 10.3866/PKU.WHXB202009080
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The growing frustration from facing energy shortages and unbalanced environmental issues has obstructed the long-term development of human society. Semiconductor-based photocatalysis, such as water splitting, transfers solar energy to storable chemical energy and is widely considered an economic and clean solution. Although regarded as a promising photocatalyst, the low specific surface area of g-C3N4 crucially restrains its photocatalytic performance. The macro-mesoporous architecture provides effective channels for mass transfer and full-light utilization and improved the efficiency of the photocatalytic reaction. Herein, g-C3N4 with an inverse opal (IO) structure was rationally fabricated using a well-packed SiO2 template, which displayed an ultrahigh surface area (450.2 m2·g-1) and exhibited a higher photocatalytic H2 evolution rate (21.22 μmol·h-1), almost six times higher than that of bulk g-C3N4 (3.65 μmol·h-1). The IO g-C3N4 demonstrates better light absorption capacity than bulk g-C3N4, primarily in the visible spectra range, owing to the multiple light scattering effect of the three-dimensional (3D) porous structure. Meanwhile, a lower PL intensity, longer emission lifetime, smaller Nyquist semicircle, and stronger photocurrent response (which synergistically give rise to the suppressed recombination of charge carriers) decrease the interfacial charge transfer resistance and boost the formation of photogenerated electron-hole pairs. Moreover, the existing N vacancies intensify the local electron density, helping increase the number of photoexcitons. The N2 adsorption-desorption test revealed the existence of ample mesopores and macropores and high specific surface area in IO g-C3N4, which exposes more active edges and catalytic sites. Optical behavior, electron paramagnetic resonance, and electrochemical characterization results revealed positive factors, including enhanced light utilization, improved photogenerated charge separation, prolonged lifetime, and fortified IO g-C3N4 with excellent photocatalytic performance. This work provides an important contribution to the structural design and property modulation of photocatalysts.
2D/2D Black Phosphorus/g-C3N4 S-Scheme Heterojunction Photocatalysts for CO2 Reduction Investigated using DFT Calculations
Xingang Fei, Haiyan Tan, Bei Cheng, Bicheng Zhu, Liuyang Zhang
2021, 37(6): 2010027-0  doi: 10.3866/PKU.WHXB202010027
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Photocatalytic reduction of CO2 to hydrocarbon compounds is a promising method for addressing energy shortages and environmental pollution. Considerable efforts have been devoted to exploring valid strategies to enhance photocatalytic efficiency. Among various modification methods, the hybridization of different photocatalysts is effective for addressing the shortcomings of a single photocatalyst and enhancing its CO2 reduction performance. In addition, metal-free materials such as g-C3N4 and black phosphorus (BP) are attractive because of their unique structures and electronic properties. Many experimental results have verified the superior photocatalytic activity of a BP/g-C3N4 composite. However, theoretical understanding of the intrinsic mechanism of the activity enhancement is still lacking. Herein, the geometric structures, optical absorption, electronic properties, and CO2 reduction reaction processes of 2D/2D BP/g-C3N4 composite models are investigated using density functional theory calculations. The composite model consists of a monolayer of BP and a tri-s-triazine-based monolayer of g-C3N4. Based on the calculated work function, it is inferred that electrons transfer from g-C3N4 to BP owing to the higher Fermi level of g-C3N4 compared with that of BP. Furthermore, the charge density difference suggests the formation of a built-in electric field at the interface, which is conducive to the separation of photogenerated electron-hole pairs. The optical absorption coefficient demonstrates that the light absorption of the composite is significantly higher than that of its single-component counterpart. Integrated analysis of the band edge potential and interfacial electronic interaction indicates that the migration of photogenerated charge carriers in the BP/g-C3N4 hybrid follows the S-scheme photocatalytic mechanism. Under visible-light irradiation, the photogenerated electrons on BP recombine with the photogenerated holes on g-C3N4, leaving photogenerated electrons and holes in the conduction band of g-C3N4 and the valence band of BP, respectively. Compared with pristine g-C3N4, this S-scheme heterojunction allows efficient separation of photogenerated charge carriers while effectively preserving strong redox abilities. Additionally, the possible reaction path for CO2 reduction on g-C3N4 and BP/g-C3N4 is discussed by computing the free energy of each step. It was found that CO2 reduction on the composite occurs most readily on the g-C3N4 side. The reaction path on the composite is different from that on g-C3N4. The heterojunction reduces the maximum energy barrier for CO2 reduction from 1.48 to 1.22 eV, following the optimal reaction path. Consequently, the BP/g-C3N4 heterojunction is theoretically proven to be an excellent CO2 reduction photocatalyst. This work is helpful for understanding the effect of BP modification on the photocatalytic activity of g-C3N4. It also provides a theoretical basis for the design of other high-performance CO2 reduction photocatalysts.
All Organic S-Scheme Heterojunction PDI-Ala/S-C3N4 Photocatalyst with Enhanced Photocatalytic Performance
Xibao Li, Jiyou Liu, Juntong Huang, Chaozheng He, Zhijun Feng, Zhi Chen, Liying Wan, Fang Deng
2021, 37(6): 2010030-0  doi: 10.3866/PKU.WHXB202010030
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Organic photocatalysts have attracted attention owing to their suitable redox band positions, low cost, high chemical stability, and good tunability of their framework and electronic structure. As a novel organic photocatalyst, PDI-Ala (N, N'-bis(propionic acid)-perylene-3, 4, 9, 10-tetracarboxylic diimide) has strong visible-light response, low valence band position, and strong oxidation ability. However, the low photogenerated charge transfer rate and high carrier recombination rate limit its application. Due to the aromatic heterocyclic structure of g-C3N4 and large delocalized π bond in the planar structure of PDI-Ala, g-C3N4 and PDI-Ala can be tightly combined through π–π interactions and N―C bond. The band structure of sulfur-doped g-C3N4 (S-C3N4) matched well with PDI-Ala than that with g-C3N4. The electron delocalization effect, internal electric field, and newly formed chemical bond jointly promote the separation and migration of photogenerated carriers between PDI-Ala and S-C3N4. To this end, a novel step-scheme (S-scheme) heterojunction photocatalyst comprising organic semiconductor PDI-Ala and S-C3N4 was prepared by an in situ self-assembly strategy. Meanwhile, PDI-Ala was self-assembled by transverse hydrogen bonding and longitudinal π–π stacking. The crystal structure, morphology, valency, optical properties, stability, and energy band structure of the PDI-Ala/S-C3N4 photocatalysts were systematically analyzed and studied by various characterization methods such as X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectrometry, X-ray photoelectron spectroscopy, ultraviolet visible diffuse reflectance spectroscopy, electrochemical impedance spectroscopy, and Mott-Schottky curve. The work functions and interface coupling characteristics were determined using density functional theory. The photocatalytic activities of the synthesized photocatalyst for H2O2 production and the degradation of tetracycline (TC) and p-nitrophenol (PNP) under visible-light irradiation are discussed. The PDI-Ala/S-C3N4 S-scheme heterojunction with band matching and tight interface bonding accelerates the intermolecular electron transfer and broadens the visible-light response range of the heterojunction. In addition, in the processes of the PDI-Ala/S-C3N4 photocatalytic degradation reaction, a variety of active species (h+, ·O2-, and H2O2) were produced and accumulated. Therefore, the PDI-Ala/S-C3N4 heterojunction exhibited enhanced photocatalytic performance in the degradation of TC, PNP, and H2O2 production. Under visible-light irradiation, the optimum 30%PDI-Ala/S-C3N4 removed 90% of TC within 90 min. In addition, 30%PDI-Ala/S-C3N4 displayed the highest H2O2 evolution rate of 28.3 μmol·h-1·g-1, which was 2.9 and 1.6 times higher than those of PDI-Ala and S-C3N4, respectively. These results reveal that the all organic photocatalyst comprising PDI-based supramolecular and S-C3N4 can be efficiently applied for the degradation of organic pollutants and production of H2O2. This work not only provides a novel strategy for the design of all organic S-scheme heterojunctions but also provides a new insight and reference for understanding the structure–activity relationship of heterostructure catalysts with effective interface bonding.
Constructing 1D/2D Schottky-Based Heterojunctions between Mn0.2Cd0.8S Nanorods and Ti3C2 Nanosheets for Boosted Photocatalytic H2 Evolution
Zhimin Jiang, Qing Chen, Qiaoqing Zheng, Rongchen Shen, Peng Zhang, Xin Li
2021, 37(6): 2010059-0  doi: 10.3866/PKU.WHXB202010059
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Sustainable photocatalytic H2 evolution has attracted extensive attention in recent years because it can address both energy shortage and environmental pollution issues. In particular, metal sulfide solid-solution photocatalysts have been widely applied in photocatalytic hydrogen generation owing to their excellent light harvesting properties, narrow enough band gap, and suitable redox potentials of conduction and valance bands. However, it is still challenging to develop low-cost and high-efficiency sulfide solid-solution photocatalysts for practical photocatalytic hydrogen evolution. Recently, 1D MnxCd1-xS nanostructures have shown superior light absorption, charge separation, and H2-evolution activity owing to their shortened diffusion pathway of carriers and high length-to-diameter ratios. Thus, 1D MnxCd1-xS nanostructures have been applied in photocatalytic H2 evolution. However, a single MnxCd1-xS photocatalyst still has some disadvantages for photocatalytic H2 evolution, such as the rapid recombination of photogenerated electron-hole pairs and low quantum efficiency. Herein, to further boost the separation of photogenerated charge carriers and H2-evolution kinetics, an in situ solvothermal method was used to synthesize the 1D/2D Schottky-based heterojunctions between the Mn0.2Cd0.8S nanorods (MCS NRs) and Ti3C2 MXene nanosheets (NSs). Furthermore, various characterization methods have been used to investigate the crucial roles and underlying mechanisms of metallic Ti3C2 MXene NSs in boosting the photocatalytic H2 evolution over the Mn0.2Cd0.8S nanorods. X-ray Diffraction (XRD), Transmission Electron Microscope (TEM), High Resolution Transmission Electron Microscopy (HRTEM), element mapping images, and X-ray Photoelectron Spectroscopy (XPS) results clearly demonstrate that hybrid low-cost Schottky-based heterojunctions have been successfully constructed for practical applications in photocatalytic H2 evolution. Additionally, the photocatalytic hydrogen evolution reaction (HER) was also carried out in a mixed solution of Na2SO3 and Na2S using as the sacrificial agents. The highest hydrogen evolution rate of the optimized 1D/2D Schottky-based heterojunction is 15.73 mmol·g-1·h-1, which is 6.72 times higher than that of pure MCS NRs (2.34 mmol·g-1·h-1). An apparent quantum efficiency of 19.6% was achieved at 420 nm. The stability measurements of the binary photocatalysts confirmed their excellent photocatalytic stability for practical applications. More interestingly, the UV-Vis diffuse reflection spectra, photoluminescence (PL) spectrum, transient photocurrent responses, and Electrochemical Impedance Spectroscopy (EIS) Nyquist plots clearly confirmed the promoted charge separation between the MCS NRs and Ti3C2 MXene NSs. The linear sweep voltammetry also showed that the loading of MXene cocatalysts could greatly decrease the overpotential of pure MCS NRs, suggesting that the 2D Ti3C2 NSs could act as an electronic conductive bridge to improve the H2-evolution kinetics. In summary, these results show that the 2D/1D hybrid Schottky-based heterojunctions between metallic Ti3C2 MXene NSs and MCS NRs can not only improve the separation of photogenerated electrons and holes but also decrease the H2-evolution overpotential, thus resulting in significantly enhanced photocatalytic H2 generation. We believe that this study will inspire new ideas for constructing low-cost Schottky-based heterojunctions for practical applications in photocatalytic H2 evolution.
Fabrication of Graphene Quantum Dots Modified BiOI/PAN Flexible Fiber with Enhanced Photocatalytic Activity
Rongan He, Rong Chen, Jinhua Luo, Shiying Zhang, Difa Xu
2021, 37(6): 2011022-0  doi: 10.3866/PKU.WHXB202011022
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In environment remediation, photocatalytic oxidation is a promising technique for removing organic pollutants. Compared to adsorption, biodegradation, and chemical oxidation, photocatalytic oxidation can eliminate organic pollutants completely, conveniently, and cheaply in an environmentally friendly manner. Visible-light-driven photocatalytic oxidation is particularly advisable because of the high proportion of visible light energy in solar energy. Bismuth oxyiodide (BiOI) is a promising visible-light-driven photocatalyst for the oxidization of pollutants, not only because of its narrow band gap, but also for its relatively low valence band (VB), which is adequate for photogenerated holes to oxidize a variety of organic compounds. However, the shortcomings of BiOI powder, such the difficulty of recycling it, its low surface area, and fast carrier recombination, limit its practical applications. Meanwhile, the flexibility and hierarchical structure of photocatalysts are particularly advisable because these properties are beneficial for the convenient operation, recycling, and performance improvement of these materials. Herein, based on an electro-spun polyacrylonitrile (PAN) nanofiber substrate, a hierarchical BiOI/PAN fiber was prepared through an in situ reaction. In the as-prepared BiOI/PAN fibers, BiOI flakes were aligned vertically and uniformly around the PAN fibers. BiOI nuclei generated from pre-introduced Bi(Ⅲ) in the PAN fiber act as seeds for the growth of BiOI nanoplates, which is crucial for the formation of a hierarchical structure. Such a hierarchical structure can improve both the light absorption and carrier generation of the BiOI/PAN fibers, as demonstrated by UV-Vis diffuse reflectance spectra and photoluminescence emission. Therefore, the BiOI/PAN fibers exhibited higher photocatalytic activity than BiOI powder. When the BiOI/PAN fibers were decorated with pre-prepared graphene quantum dots (GQDs), a GQD-modified BiOI/PAN fibrous composite (GQD-BiOI/PAN) was fabricated. The morphology of the obtained GQD-BiOI/PAN fibers was nearly the same as that of the BiOI/PAN fibers. A step-scheme (S-scheme) heterojunction was formed between the GQDs and BiOI, which was confirmed by the fabrication method, photoluminescence emission, reactive radical tests, and XPS analysis. This kind of S-scheme heterojunction can not only effectively suppress the recombination of photogenerated holes, but can also reserve the more reductive electrons on the lowest unoccupied molecular orbital of GQDs and the more oxidative holes on the VB of BiOI, for the photocatalytic degradation of phenol. Because of the fibrous hierarchical structure and S-scheme heterojunction, GQD-BiOI/PAN outperformed BiOI nanoparticles and BiOI/PAN nanofibers in the photocatalytic oxidation of phenol under visible light. In addition, because of tight bonding, GQD-BiOI/PAN can be tailored and operated by hand, which is convenient for recycling. During recycling, no obvious loss of sample or decrease in photocatalytic activity was observed. This work provides a new pathway for the fabrication of flexible photocatalysts and a new insight into the enhancement of photocatalysts.
Review
TiO2-Supported Single-Atom Catalysts for Photocatalytic Reactions
Xuemei Zhou
2021, 37(6): 2008064-0  doi: 10.3866/PKU.WHXB202008064
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Titania (TiO2) has been among the most widely investigated and used metal oxides over the past years, as it has various functional applications. Extensive research into TiO2 and industrial interest in this material have been triggered by its high abundance, excellent corrosion resistance, and low cost. To improve the activity of TiO2 in heterogeneous catalytic reactions, noble metals are used to accelerate the reactions. However, in the case of nanoparticles supported on TiO2, the active sites are usually limited to the peripheral sites of the noble metal particles or at the interface between the particle and the support. Thus, highly dispersed single metal atoms are desired for the effective utilization of precious noble metals. The study of oxide-supported isolated atoms, the so-called single-atom catalysts (SACs), was pioneered by Zhang's group. The high dispersion of precious noble metals results helps reduce the cost associated with catalyst preparation. Because of the presence of active centers as single atoms, the deactivation of metal atoms during the reaction, e.g., by coking for large agglomerates, is retarded. The unique coordination environment of the noble metal center provides special sites for the reaction, consequently increasing the selectivity of the reaction, including the enantioselectivity and stereoselectivity. Hence, supported SACs can bridge homogenous and heterogeneous reactions in solution as they provide selective reaction sites and are recyclable. Moreover, owing to the high site homogeneity of the isolated metal atoms, SACs are ideal models for establishing the structure-activity relationships. The present review provides an overview of recent works on the synthesis, characterization, and photocatalytic applications of SACs (Pt1, Pd1, Ir1, Rh1, Cu1, Ru1) supported on TiO2. The preparation of single atoms on TiO2 includes the creation of surface defective sites, surface modification, stabilization by high-temperature shockwave treatment, and metal-ligand self-assembly. Conventional characterization methods are categorized as microscopic imaging and spectroscopic methods, such as aberration-corrected scanning transmission electron microscopy (STEM), scanning tunneling microscopy (STM), extended X-ray absorption fine structure analysis (EXAFS), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). We attempted to address the critical factors that lead to the stabilization of single-metal atoms on TiO2, and elucidate the mechanism underlying the photocatalytic hydrogen evolution and CO2 reduction. Although many fascinating applications of TiO2-supported SACs in photocatalysis could only be addressed superficially and in a referencing manner, we hope to provide interested readers with guidelines based on the wide literature, and more specifically, to provide a comprehensive overview of TiO2-supported SACs.
Recent Advances in Surface-Modified g-C3N4-Based Photocatalysts for H2 Production and CO2 Reduction
Yunfeng Li, Min Zhang, Liang Zhou, Sijia Yang, Zhansheng Wu, Ma Yuhua
2021, 37(6): 2009030-0  doi: 10.3866/PKU.WHXB202009030
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Solar energy is the largest renewable energy source in the world and the primary energy source of wind energy, tidal energy, biomass energy, and fossil fuel. Photocatalysis technology is a sunlight-driven chemical reaction process on the surface of photocatalysts that can generate H2 from water, decompose organic contaminants, and reduce CO2 into organic fuels. As a metal-free polymeric material, graphite-like carbon nitride (g-C3N4) has attracted significant attention because of its special band structure, easy fabrication, and low costs. However, some bottlenecks still limit its photocatalytic performance. To date, numerous strategies have been employed to optimize the photoelectric properties of g-C3N4, such as element doping, functional group modification, and construction of heterojunctions. Remarkably, these modification strategies are strongly associated with the surface behavior of g-C3N4, which plays a key role in efficient photocatalytic performance. In this review, we endeavor to provide a comprehensive summary of g-C3N4-based photocatalysts prepared through typical surface modification strategies (surface functionalization and construction of heterojunctions) and elaborate their special light-excitation and response mechanism, photo-generated carrier transfer route, and surface catalytic reaction in detail under visible-light irradiation. Moreover, the potential applications of the surface-modified g-C3N4-based photocatalysts for photocatalytic H2 generation and reduction of CO2 into fuels are summarized. Finally, based on the current research, the key challenges that should be further studied and overcome are highlighted. The following are the objectives that future studies need to focus on: (1) Although considerable effort has been made to develop a surface modification strategy for g-C3N4, its photocatalytic efficiency is still too low to meet industrial application standards. The currently obtained solar-to‑hydrogen (STH) conversion efficiency of g-C3N4 for H2 generation is approximately 2%, which is considerably lower than the commercial standards of 10%. Thus, the regulation of the surface/textural properties and electronic band structure of g-C3N4 should be further elucidated to improve its photocatalytic performance. (2) Significant challenges remain in the design and construction of g-C3N4-based S-scheme heterojunction photocatalysts by facile, low-cost, and reliable methods. To overcome the limitations of conventional heterojunctions thoroughly, a promising S-scheme heterojunction photocatalytic system was recently reported. The study further clarifies the charge transfer route and mechanism during the catalytic process. Thus, the rational design and synthesis of g-C3N4-based S-scheme heterojunctions will attract extensive scientific interest in the next few years in this field. (3) First-principle calculation is an effective strategy to study the optical, electrical, magnetic, and other physicochemical properties of surface strategy modified g-C3N4, providing important information to reveal the charge transfer path and intrinsic catalytic mechanism. As a result, density functional theory (DFT) computation will be paid increasing attention and widely applied in surface-modified g-C3N4-based photocatalysts.
Review of Z-Scheme Heterojunctions for Photocatalytic Energy Conversion
Dong Liu, Shengtao Chen, Renjie Li, Tianyou Peng
2021, 37(6): 2010017-0  doi: 10.3866/PKU.WHXB202010017
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Inspired by the photosynthesis of green plants, various artificial photosynthetic systems have been proposed to solve the energy shortage and environmental problems. Water photosplitting, carbon dioxide photoreduction, and nitrogen photofixation are the main systems that are used to produce solar fuels such as hydrogen, methane, or ammonia. Although conducting artificial photosynthesis using man-made semiconducting materials is an ideal and potential approach to obtain solar energy, constructing an efficient photosynthetic system capable of producing solar fuels at a scale and cost that can compete with fossil fuels remains challenging. Therefore, exploiting the efficient and low-cost photocatalysts is crucial for boosting the three main photocatalytic processes (light-harvesting, surface/interface catalytic reactions, and charge generation and separation) of artificial photosynthetic systems. Among the various photocatalysts developed, the Z-scheme heterojunction composite system can increase the light-harvesting ability and remarkably suppress charge carrier recombination; it can also promote surface/interface catalytic reactions by preserving the strong reductive/oxidative capacity of the photoexcited electrons/holes, and therefore, it has attracted considerable attention. The continuing progress of Z-scheme nanostructured heterojunctions, which convert solar energy into chemical energy through photocatalytic processes, has witnessed the importance of these heterojunctions in further improving the overall efficiency of photocatalytic reaction systems for producing solar fuels. This review summarizes the progress of Z-scheme heterojunctions as photocatalysts and the advantages of using the direct Z-scheme heterojunctions over the traditional type Ⅱ, all-solid-state Z-schemel, and liquid-phase Z-scheme ones. The basic principle and corresponding mechanism of the two-step excitation are illustrated. In particular, applications of various types of Z-scheme nanostructured materials (inorganic, organic, and inorganic-organic hybrid materials) in photocatalytic energy conversion and different controlling/engineering strategies (such as extending the spectral absorption region, promoting charge transfer/separation and surface chemical modification) for enhancing the photocatalytic efficiency in the last five years are highlighted. Additionally, characterization methods (such as sacrificial reagent experiment, metal loading, radical trapping testing, in situ X-ray photoelectron spectroscopy, photocatalytic reduction experiments, Kelvin probe force microscopy, surface photovoltage spectroscopy, transient absorption spectroscopy, and theoretical calculation) of the Z-scheme photocatalytic mechanism, and the assessment criteria and methods of the photocatalytic performance are discussed. Finally, the challenges associated with Z-scheme heterojunctions and the possible growing trend are presented. We believe that this review will provide a new understanding of the breakthrough direction of photocatalytic performance and provide guidance for designing and constructing novel Z-scheme photocatalysts.
Recent Progress of Perovskite Oxide in Emerging Photocatalysis Landscape: Water Splitting, CO2 Reduction, and N2 Fixation
Zejian Wang, Jiajia Hong, Sue-Faye Ng, Wen Liu, Junjie Huang, Pengfei Chen, Wee-Jun Ong
2021, 37(6): 2011033-0  doi: 10.3866/PKU.WHXB202011033
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At present, more than 80% of the world's energy demand is fulfilled by the burning of fossil fuels, which has caused the production of a large amount of greenhouse gases, leading to global warming and damage to the environment. The high consumption of fossil fuels every year causes the energy crisis to become increasingly serious. Finding a sustainable and pollution-free energy source is therefore essential. Among all forms of energy sources, solar energy is preferred because of its cleanliness and inexhaustible availability. The energy provided by one year of sunlight is more than 100 times the total energy in known fossil fuel reserves worldwide; however, the extent of solar energy currently used by mankind each year is minute; thus developments in solar energy are imperative. To address the urgent need for a renewable energy supply and to solve environmental problems, a variety of technologies in the field of photocatalysis have been developed. Photocatalytic technology has attracted significant attention because of its superior ability to convert clean solar energy into chemical fuels. Among the photocatalytic materials emerging in an endless stream, perovskite oxide, with the general formula of ABO3, has great potential in the fields of solar cells and photocatalysis as each site can be replaced by a variety of cations. Furthermore, owing to its unique properties such as high activity, robust stability, and facile structure adjustment, perovskite oxide photocatalysts have been widely used in water decomposition, carbon dioxide reduction and conversion, and nitrogen fixation. In terms of carbon dioxide reduction, oxide perovskites can achieve precise band gap and band edge tuning owing to its long charge diffusion length and flexibility in composition. For the development and utilization of solar energy in the environmental field, perovskite oxide and its derivatives (layered perovskite oxide) are used as photocatalysts for water decomposition and environmental remediation. In terms of nitrogen fixation, the conventional Haber-Bosh process for ammonia synthesis, which has been widely used in the past, requires high temperature and high energy. Therefore, we summarize the recent advances in perovskite oxide photocatalysts for nitrogen fixation from the aspect of activating the adsorbed N2 by weakening the N \begin{document}$ \equiv $\end{document}N triple bond, promoting charge separation, and accelerating the charge transfer to the active sites to realize the photochemical reaction. Overall, this review article presents the structure and synthesis of perovskite oxide photocatalysis, focusing on the application of photocatalysis in water splitting, carbon dioxide reduction, and nitrogen fixation. This review concludes by presenting the current challenges and future prospects of perovskite oxide photocatalysts.
Fluorinated TiO2 Hollow Photocatalysts for Photocatalytic Applications
Jiabi Li, Xi Wu, Shengwei Liu
2021, 37(6): 200903038-0  doi: 10.3866/PKU.WHXB202009038
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Recently, extensive studies have been carried out to synthesize spherical microassemblies with hollow interiors and specific surface functionalizations, which usually exhibit fascinating enhanced or emerging properties and have promising applications in catalysis, photocatalysis, energy conversion and storage, biomedical applications, etc. With particular emphasis on the results obtained mainly by the authors' research group, this review provides a brief summary of the recent progress on the fabrication and potential photocatalytic applications of fluorinated TiO2 porous hollow microspheres(F-TiO2 PHMs). The synthesis strategies for F-TiO2 PHMs include a simplified two-step templating method and template-free method based on the fluoride-mediated self-transformation(FMST) mechanism. Compared to the two-step templating method, the template formation, coating, and removal steps for the FMST method are programmatically proceeded in "black-box"-like one-pot reactions without additional manual steps. The four underlying steps involved in the fabrication of F-TiO2 PHMs through the FMST pathway, nucleation, self-assembly, surface recrystallization, and self-transformation, are presented. By controlling these four steps in the FMST pathway, F-TiO2 PHMs can be successfully fabricated with a high yield by a simple one-pot hydrothermal treatment. The multi-level microstructural characteristics(including the interior cavity and hierarchical porosity) and compositions of hollow TiO2 microspheres as well as the primary building blocks can be well tailored. The unique superstructures of the F-TiO2 PHM photocatalysts provide advantages for photocatalytic applications by improving the light harvesting, mass transfer, and membrane antifouling. In addition, the in situ-introduced surface fluorine species during the formation of F-TiO2 PHMs provide significant surface fluorination effects, which are not only favorable for the adsorption and activation of reactant molecules, but also beneficial for surface trapping and interfacial transfer of photo-excited electrons and holes. Moreover, the porous hollow superstructures exhibit considerably better compatibility and tolerance to guest modifications, and thus the photocatalytic performances of F-TiO2 PHMs can be increased by synergetic host and guest modifications, such as ion doping, group functionalization, and nanoparticle loading. The light-harvesting range and intensity can be increased, the charge recombination can be reduced, mass transfer and adsorption can be promoted, and the surface reactivity can be tuned by introducing specific surface functionalities or nanoparticular cocatalysts. Consequently, the entire photocatalytic process can be systematically modulated to optimize the overall photocatalytic performance. The as-prepared F-TiO2 PHMs typically integrate the merits of interior cavity, hierarchical porosity, and surface fluorination and are open to synergetic host-guest modifications, which provides abundant compositional/structural parameters and specific physicochemical properties for systematically modulating the interconnected photocatalytic processes and promising potential photocatalytic applications.
论文
微波辅助快速制备2D/1D ZnIn2S4/TiO2 S型异质结及其光催化制氢性能
梅子慧, 王国宏, 严素定, 王娟
2021, 37(6): 2009097-0  doi: 10.3866/PKU.WHXB202009097
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能源危机的威胁在过去二十年里引起了全球性广泛关注。由于地球上具有丰富的太阳能和水资源,光催化分解水制氢被认为是获取绿色能源的一种有效途径。迄今为止,许多光催化剂已经得到了深入研究。其中,TiO2以其无毒、化学稳定性高、形态可控、光催化活性强等优点得到了广泛的关注。特别是1D结构的TiO2纳米纤维具有独特的一维电子转移轨迹,较大的吸附能力和较高的光生电子-空穴对(e--h+)传输速率等优点在光催化领域更是受到研究人员的青睐。尽管如此,TiO2仍存在带隙大、光生电子-空穴对复合速率快等缺点,使其在制氢反应(HER)中效率不高。因此,构建高性能、经济、环保的光催化剂是实现太阳能高效转化的一大挑战。最近,各种提高TiO2光催化活性的策略得到了广泛研究,包括与窄带隙半导体(如ZnIn2S4)的耦合等。另外,微波辅助合成技术以其成本低、设备简单、环境无污染、反应速度快等优点,已成为制备光催化半导体材料的一种重要手段。在本工作中,为解决TiO2带隙宽(约3.2 eV)和电子-空穴对复合速率快等缺点,通过微波辅助合成技术快速地将2D结构的ZnIn2S4纳米片原位组装在TiO2纳米纤维上,构筑2D/1D ZnIn2S4/TiO2 S型异质结。通过调节ZnIn2S4前驱体与TiO2 NFs的摩尔比,可以很容易地控制TiO2纳米纤维上ZnIn2S4负载量。实验结果表明:相对于纯ZnIn2S4和TiO2而言,ZnIn2S4/TiO2异质结光催化剂在太阳光照射下的光吸收和制氢性能得到明显提高。在优化条件下,样品ZT-0.5 (ZnIn2S4与TiO2的摩尔比为0.5)具有最佳制氢性能,达到8774 μmol·g-1·h-1,分别是纯TiO2纳米纤维(3312 μmol·g-1·h-1)和ZnIn2S4 (3114 μmol·g-1·h-1)纳米片的2.7倍和2.8倍。基于实验结果,我们提出来一种在ZnIn2S4和TiO2间形成的S型异质结机理,并很好地阐释了ZnIn2S4/TiO2复合材料光催化制氢活性增强的原因。
Highlight
S-Scheme Heterojunction Photocatalyst for CO2 Photoreduction
Swelm Wageh, Ahmed A. Al-Ghamdi, Lijun Liu
2021, 37(6): 2010024-0  doi: 10.3866/PKU.WHXB202010024
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前言
先进光催化剂设计与制备
余家国, 李鑫, 王伟俊, 张留洋
2021, 37(6): 2012043-0  doi: 10.3866/PKU.WHXB202012043
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论文
原位聚合表面修饰的金属锂负极
刘亚, 郑磊, 谷巍, 沈炎宾, 陈立桅
2021, 37(1): 2004058-0  doi: 10.3866/PKU.WHXB202004058
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金属锂负极由于比容量高(3860 mAh·g-1)及氧化还原电位极低(-3.04 V vs.标准氢气电极(SHE)),被认为是实现高能量密度锂电池的理想负极。然而,金属锂电极与电解液反应剧烈,且锂离子在电极表面沉积不均匀容易产生枝晶,导致其循环稳定性和安全性都较差,限制了其应用推广。我们前期通过构建金属锂-碳纳米管(Li-CNT)复合结构,极大的提高了金属锂的比表面积,降低了电极电流密度,从而有效地抑制了锂枝晶的生长,提高了金属锂电极的循环稳定性和安全性能。本工作在前期工作基础上,采用简单的液相反应,利用4-氟苯乙烯(FPS)对Li-CNT进行表面修饰并进行原位聚合,得到了表面富含氟化锂(LiF)保护层的Li-CNT(FPS-Li-CNT)。该表面修饰层能够有效抑制电解液和空气对Li-CNT的侵蚀,显著的提高了Li-CNT电极的界面稳定性。FPS-Li-CNT与磷酸铁锂正极(LFP)组成的LFP||FPS-Li-CNT全电池,在正负极容量配比为1 : 6条件下,能够稳定循环280圈,库伦效率达到97.7%。
柱状金属锂沉积物:电解液添加剂的影响
杨世杰, 徐向群, 程新兵, 王鑫萌, 陈金秀, 肖也, 袁洪, 刘鹤, 陈爱兵, 朱万诚, 黄佳琦, 张强
2021, 37(1): 2007058-0  doi: 10.3866/PKU.WHXB202007058
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二次电池的能量密度已成为推动电动汽车和便携式电子产品技术向前发展的重要指标。使用石墨负极的锂离子电池正接近其理论能量密度的天花板,但仍难以满足高端储能设备的需求。金属锂负极因其极高的理论比容量和极低的电极电位,受到了广泛关注。然而,锂沉积过程中枝晶的生长会导致电池安全性差等问题。电解液对金属锂的沉积有着至关重要的影响。本文设计了一种独特的电解槽体系来进行柱状锂的沉积,研究了不同电解液体系(1 mol·L-1 LiPF6-碳酸乙烯酯/碳酸二乙酯(EC/DEC,体积比为1 : 1)、1 mol·L-1 LiPF6-氟代碳酸乙烯酯(FEC,体积分数5%)-EC/DEC (体积比为1 : 1))对金属锂沉积的影响。对两种电解液中金属锂沉积物长径比的研究表明,电解液的组分可以显著地影响金属锂的沉积形貌,在加入氟代碳酸乙烯酯(FEC)添加剂之后,柱状锂的直径从0.3–0.6 μm增加到0.7–1.3 μm,长径比从12.5下降到5.6。长径比的降低有助于减小金属锂和电解液的反应面积,提高金属锂负极的利用率和循环寿命。通过考察循环后锂片的表面化学性质,发现FEC的分解增加了锂表面固态电解质界面层中氟化锂(LiF)组分的比例,提高了界面层中锂离子的扩散速率,减少了锂的成核位点,从而给予锂核更大的生长空间,降低了沉积出的柱状锂的长径比。
亲锂的三维二硫化锡@碳纤维布用于稳定的锂金属负极
王骞, 吴恺, 王航超, 刘文, 周恒辉
2021, 37(1): 2007092-0  doi: 10.3866/PKU.WHXB202007092
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金属锂由于其高的比容量,低的电极电势和轻质等特点被认为是下一代高能量密度锂金属二次电池负极材料的最佳选择。然而,充放电循环中不均匀的锂沉积会导致严重的体积变化和大量的锂枝晶形成,从而影响了电池的库伦效率甚至会带来严重的安全隐患。为此,本文设计了一种亲锂的三维二硫化锡@碳纤维布复合基底材料,并作为集流体将其应用于金属锂电池上。一者,高比表面积的三维碳纤维骨架可以适应充放电过程中的体积变化并且有效地降低局部电流密度,从而确保锂的均匀沉积。二者,表面修饰的SnS2层在锂沉积过程中可以形成Li-Sn合金界面层,诱导锂的沉积并降低过电势。最终,实验结果表明:使用所制备的复合集流体与金属锂搭配组成的半电池可以在5 mA·cm-2的高电流密度下以 > 98%的库伦效率稳定循环100周以上。此外,在承载10 mAh·cm-2的金属锂后,复合的锂负极无论是在对称电池还是与磷酸铁锂组装成的实际电池中,均可以在高的电流密度下实现稳定的循环。我们相信这一复合的集流体构建策略对于设计安全稳定的锂金属电池或器件具有重要意义。
锂金属负极的可逆性与沉积形貌的关联
黄凡洋, 揭育林, 李新鹏, 陈亚威, 曹瑞国, 章根强, 焦淑红
2021, 37(1): 2008081-0  doi: 10.3866/PKU.WHXB202008081
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摘要:
高能量密度二次电池的商业化将会推动便携式电子设备和电动车的飞速发展。锂金属电池因具有较高的理论能量密度而受到研究者的广泛关注。然而,锂金属负极较低的库仑效率(CE)和枝晶生长等问题,严重制约了锂金属电池的发展。库仑效率是衡量电池体系可逆性的关键参数之一,锂金属负极的库仑效率在不同电解液中存在较大的差异,本文以四种常见的电解液为例,包括1 mol·L-1六氟磷酸锂-碳酸乙烯酯/碳酸二甲酯电解液,1 mol·L-1六氟磷酸锂-碳酸乙烯酯/碳酸二甲酯+ 5% (w)氟代碳酸乙烯酯电解液,1 mol·L-1双(三氟甲烷磺酰)亚胺锂-乙二醇二甲醚/1, 3二氧戊环+ 2% (w)硝酸锂电解液,以及4 mol·L-1双氟磺酰亚胺锂-乙二醇二甲醚电解液,利用原子力显微镜研究了不同电解液体系中锂金属的生长行为,探讨了锂金属沉积形貌与其库仑效率之间的联系,为发展高效的锂金属负极提供了参考依据。
多孔泡沫铜和硫脲协同作用构筑无枝晶锂负极
秦金利, 任龙涛, 曹欣, 赵亚军, 许海军, 刘文, 孙晓明
2021, 37(1): 2009020-0  doi: 10.3866/PKU.WHXB202009020
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锂金属作为下一代储能电池的理想负极材料一直受到极大的关注,然而锂枝晶的不可控生长和负极副反应带来的低库伦效率问题严重限制了锂金属电池的发展。这里, 我们提出了一种多孔泡沫铜和硫脲协同作用的策略,利用硫脲分子的超填充作用实现锂金属在多孔泡沫铜表面的均匀沉积。在电解液中添加0.02 mol·L-1硫脲作为电解质添加剂,采用多孔泡沫铜的Li||Cu半电池在循环300圈以后,库伦效率仍保持在98%以上。此外,在5C的高倍率条件下,Li||LiFePO4全电池循环300圈以后仍有94%的容量保持率。本工作为锂金属负极保护提供了一种新的策略并且该策略也可以扩展到其他金属负极保护中,非常有利于下一代高能量密度储能电池的开发。
综述
锂金属负极的挑战与改善策略研究进展
刘凡凡, 张志文, 叶淑芬, 姚雨, 余彦
2021, 37(1): 2006021-0  doi: 10.3866/PKU.WHXB202006021
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锂金属由于其高比容量和低电极电势等优点被认为是下一代高比能量电池体系中最有潜力的负极材料。然而由于锂金属的高活性,锂负极在循环过程中会产生大量的枝晶,导致SEI (solid-electrolyte interphase)破裂,并且枝晶增加了电极与电解液的接触面积,使得副反应进一步增加。此外,脱落的枝晶形成死锂,从而降低电池的充放电库仑效率。并且不可控的锂枝晶持续生长会刺穿隔膜引发电池短路,伴随着电池热失控等安全问题。本综述基于锂负极存在的主要挑战,结合理解锂枝晶的成核生长模型等机理总结并深度分析近些年来在液态和固态电解质体系中改善锂金属负极的主要策略及其作用机理,为促进高比能量锂金属电池的应用提供借鉴参考作用。
金属有机骨架材料在金属锂电池界面的应用
孙宇恒, 高铭达, 李慧, 徐丽, 薛晴, 王欣然, 白莹, 吴川
2021, 37(1): 2007048-0  doi: 10.3866/PKU.WHXB202007048
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摘要:
金属锂电池是下一代高能量密度电池体系的代表。然而,高比能金属锂电池的发展受到界面诸多问题的限制,如:金属锂负极枝晶生长、隔膜界面兼容性、正极界面不稳定等,影响了金属锂电池的界面传质传荷过程,并导致金属锂界面环境恶化、电池的容量衰减、安全性能下降等问题。金属有机骨架(MOF)是一种具有稳定多孔结构的有机无机杂化材料,近年来在高比能金属锂电池领域受到广泛关注。其多孔结构与开放的金属位点(OMs)提供了优异的离子电导率,稳定的空间结构提供了较高的机械强度,多样的官能团与金属节点带来丰富的功能性。本文分析了金属锂电池界面的主要挑战,结合金属锂界面的成核模型,总结了MOF及其衍生材料在解决锂金属负极界面、隔膜界面、以及正负极界面稳定性相互作用等方面的研究进展和作用机理,为解决高比能金属锂电池界面失稳问题提供了解决途径,并展望了MOF基材料的设计与发展方向。
金属锂电池的热失控与安全性研究进展
张世超, 沈泽宇, 陆盈盈
2021, 37(1): 2008065-0  doi: 10.3866/PKU.WHXB202008065
[摘要]  (50) [HTML全文] (50) [PDF 5459KB] (50)
摘要:
锂离子电池在便携式储能器件及电动汽车领域得到了广泛应用,然而频繁发生的电池起火爆炸事故,使热失控和热安全问题备受人们关注,目前已有多篇综述报道了缓解锂离子电池热失控的措施。相比于已经接近理论比能极限的锂离子电池,金属锂负极具有更高的比容量、更低的电势和高反应活性,但是不可控的锂枝晶生长,使得金属锂电池的热失控问题更为复杂和严重。针对金属锂电池的热失控问题,本文首先介绍了热失控的诱因及基本过程和阶段,其次从材料层面综述了提高电池热安全性的多种策略,包括使用阻燃性电解质、离子液体电解质、高浓电解质和局域高浓电解质等不易燃液态电解质体系,开发高热稳定性隔膜、热响应隔膜、阻燃性隔膜和具有枝晶检测预警与枝晶消除功能的新型智能隔膜,以及研究热响应聚合物电解质,最后对金属锂电池热失控在未来的进一步研究进行了展望。
多空间尺度下的金属锂负极表征技术
潘弘毅, 李泉, 禹习谦, 李泓
2021, 37(1): 2008091-0  doi: 10.3866/PKU.WHXB202008091
[摘要]  (45) [HTML全文] (45) [PDF 13252KB] (45)
摘要:
金属锂因为其优秀的特性被认为是未来锂电池负极的最终之选。然而目前金属锂负极在旧有液态体系中的研究陷入瓶颈,在新兴固态体系中的挑战层出不穷。想要实现金属锂负极的实用化,必须加深对金属锂负极基础科学问题的认识。本文系统论述了多空间尺度下金属锂的电极行为与对应的表征技术。首先综述了多空间尺度下金属锂负极的基础科学和应用技术问题,结合近年来的工作,对全空间尺度下的先进表征手段做了梳理,分析了从原子级到宏观尺度各种表征手段的技术特点,并重点讨论了各类表征技术在研究固态体系中金属锂负极时的特点与可能的发展方向。
中子深度剖析技术研究可充锂金属负极
郑国瑞, 向宇轩, 杨勇
2021, 37(1): 2008094-0  doi: 10.3866/PKU.WHXB202008094
[摘要]  (40) [HTML全文] (40) [PDF 5377KB] (40)
摘要:
可充锂金属负极严重的界面不稳定性和安全问题极大限制了其商业化应用,对于锂的沉积/溶出行为以及锂枝晶的成核生长机理的清楚认识将有利于更高效的可充锂金属负极改性研究。然而,由于锂金属的高反应活性所带来的产物复杂性及其形貌多样性给原位谱学表征带来了诸多的困难。中子深度剖析(Neutron Depth Profiling,NDP)技术由于其高穿透特性、定量非破坏性、且对锂的高灵敏性,在实时研究锂金属电池中锂的电化学行为上显示出广阔的应用前景。本文首先简要介绍了NDP技术的测试原理及提高其空间/时间分辨率的方法,同时总结分析了近年来NDP技术在液态/固态电池体系中锂金属负极研究的应用,并展望了NDP技术今后的发展前景。
金属锂负极的成核机制与载体修饰
邱晓光, 刘威, 刘九鼎, 李俊志, 张凯, 程方益
2021, 37(1): 2009012-0  doi: 10.3866/PKU.WHXB202009012
[摘要]  (43) [HTML全文] (43) [PDF 2394KB] (43)
摘要:
金属锂具有电位低、比容量高等突出优点,是极具吸引力的下一代高能量密度电池的负极材料,然而存在枝晶、死锂、副反应严重、库伦效率低、循环稳定性差等问题,限制了其实际应用。金属锂负极的成核是电化学沉积过程中的重要步骤,锂在集流体或导电载体上的均匀成核和稳定生长对于抑制枝晶死锂、提高充放电效率和循环性能具有关键作用。本文从成核机制与载体效应的角度概述了锂金属负极的研究进展,介绍了锂成核驱动力、异相成核模型、空间电荷模型等内容,分析了锂核尺寸及分布与过电位和电流密度的关系,并通过三维载体分散电流密度、异相晶核/电场诱导成核、晶格匹配等方面的研究实例讨论了载体修饰对锂负极的性能提升。
Article
A Framework with Enriched Fluorinated Sites for Stable Li Metal Cycling
Muqin Wang, Zhe Peng, Huan Lin, Zhendong Li, Jian Liu, Zhongmin Ren, Haiyong He, Deyu Wang
2021, 37(1): 2007016-0  doi: 10.3866/PKU.WHXB202007016
[摘要]  (39) [HTML全文] (39) [PDF 2291KB] (39)
摘要:
In past decades, lithium-ion batteries (LIBs) were the dominant energy storage systems for powering portable electronic devices because of their reliable cyclability. However, further increase in the energy density of LIBs was met by a bottleneck when low-specific- capacity graphite was used at the anode. Li metal has long been regarded as the ideal anode material for building the next high-energy-density batteries due to its ultrahigh capacity of 3860 mAh·g-1, which is ten times higher than that of graphite. However, using Li metal as an anode in rechargeable batteries is challenging due to its high uncontrolled volume expansion and aggressive side reactions with liquid electrolytes. In this study, we demonstrate the effect of a three-dimensional (3D) framework with enriched fluorinated sites for Li metal protection. This framework is obtained via a facile integration of down-sized fluorinated graphite (CFx) particles into Li+ conducting channels. Thermogravimetry, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy results show that Li+ conducting channels rich in lithium fluoride (LiF) are formed in situ across the embedded CFx particles during the initial lithiation process, leading to fast Li+ transfer. Scanning electron microscopy results show that residual CFx particles could act as high-quality nucleation sites for uniform Li deposition inside the framework. These features could not be achieved with a 2D structure consisting of large CFx flakes, due to the limited Li+ transfer paths and low utilization ratio of CFx for conversion into LiF-based solid electrolyte interphase (SEI) layers. Consequently, better performance of Li metal anodes in a 3D framework with enriched fluorinated sites is demonstrated. Stable Li plating/stripping over 240 cycles is obtained at a current density of 0.5 mA·cm-2 for a fixed capacity of 1 mAh·cm-2 by maintaining a voltage hysteresis below 80 mV. Improved Li-LiFePO4 full cell performance with a practical negative/positive capacity ratio of 3 is also demonstrated. These results show the rational combination of well-developed 3D Li+ transfer channels and enriched fluorinated sites as an optimized interfacial design beyond the single use of a 2D fluorinated interface, giving new insight into the protection of Li metal anodes in high-energy-density batteries.
通讯
水溶液法原位构建ZnO亲锂层稳定锂-石榴石电解质界面
蔡明俐, 姚柳, 靳俊, 温兆银
2021, 37(1): 2009006-0  doi: 10.3866/PKU.WHXB202009006
[摘要]  (48) [HTML全文] (48) [PDF 3436KB] (48)
摘要:
固态电池以其高安全性和高能量密度而备受关注。石榴石型固体电解质(LLZO)由于具有较高的离子导电性和对锂金属的稳定性,在固态电池中具有应用前景,但陶瓷与锂金属较差的界面接触会导致高的界面阻抗和可能形成的枝晶穿透。我们利用LLZO表层独特的H+/Li+交换反应,提出了一种简便有效的金属盐类水溶液诱发策略,在电解质表面原位构建ZnO亲锂层,界面处LiZn合金化实现紧密连续的接触。引入改性层后,界面阻抗可显著降低至约10 Ω·cm2,对称电池能够在0.1 mA·cm-2的电流密度下实现长达1000 h的长循环稳定性。匹配正极LiFePO4(LFP)或LiNi0.5Co0.2Mn0.3O2 (NCM523)的准固态电池在室温下能够稳定循环100次以上。
前言
蓬勃发展的金属锂负极
张强, 郭玉国
2021, 37(1): 2011061-0  doi: 10.3866/PKU.WHXB202011061
[摘要]  (53) [HTML全文] (53) [PDF 352KB] (53)
摘要:

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北京大学

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北京化工大学

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福州大学

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中国科学技术大学

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南京工业大学

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厦门大学

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中国科学院化学研究所

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北京大学

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Harvard University, 北京大学

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中国科学院化学研究所

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北京大学

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北京大学

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中国科学院化学研究所

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中国科学院大连化学物理研究所

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北京大学

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中国科学技术大学

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武汉大学

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复旦大学

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University of Delaware

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南开大学

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Stanford University

邓风

中国科学院武汉物理与数学研究所

邓友全

中国科学院兰州化学物理研究所

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中国科学院山西煤炭化学研究所

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陕西师范大学

付红兵

中国科学院化学研究所

傅强

中国科学院大连化学物理研究所

高毅勤

北京大学

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北京航空航天大学

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山东大学

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南京大学

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Carnegie Mellon University

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华东理工大学

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武汉大学

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中国科学院化学研究所

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中国科学院上海药物研究所

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南京大学

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中国科学院物理研究所

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国家自然科学基金委员会

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清华大学

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北京大学

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中国科学院大连化学物理研究所

张浩力

兰州大学

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北京大学

章俊良

上海交通大学

周永贵

中国科学院大连化学物理研究所

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发布时间: 2018-05-02


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发布日期:2009-06-24 浏览: