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2024 Volume 40 Issue 10
2024, 40(10): 230902
doi: 10.3866/PKU.WHXB202309020
Abstract:
Artificial photosynthesis is an appealing approach for generating hydrogen peroxide (H2O2) from H2O and O2 with solar energy as the sole energy input. However, the current catalyst systems commonly face challenges such as the limited optical absorption, poor electron-hole pair separation efficiency, and restricted surface reactivity, which hinders the overall photoactivity. Here, we immobilize cubic-phase ultrathin In4SnS8 nanosheets (Eg=2.16 eV) with thickness of 5-10 nm on the surface of few-layer Ti3C2 to develop a sandwich-like hierarchical structure of Ti3C2/In4SnS8 nanohybrid via in situ hydrothermal strategy. The enlarged interfacial area and close contact between Ti3C2 and In4SnS8 benefit for carrier transportation among nanohybrids. Characterization through X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) corroborates the successful construction of Ti3C2/In4SnS8 nanostructures. Band structures investigation including valence band maximum and Mott-Schottky plots reveals the formation of Schottky junction in this 2D/2D heterostructure, that favors for ultrafast charge carrier separation and transportation from In4SnS8 to Ti3C2 and preventing the electrons backflow from Ti3C2 to In4SnS8. Photoluminescene analysis and photo/electrochemical measurements prove that the combination of Ti3C2 and In4SnS8 accelerates the transportation of photoexcited electron-hole pairs and efficiently suppresses charge carrier recombination. Unsurprisingly, 7 wt% Ti3C2/In4SnS8 catalysts exhibit the highest visible-light-driven photoreactivity with H2O2 production rates of 1.998 μmol·L-1·min-1 that is 2.2 times larger than that of single In4SnS8. Additionally, Ti3C2/In4SnS8 demonstrates a multifunctional capability in Cr(VI) reduction with the greatest reaction rates of 19.8×10-3 min-1 that is almost 4-fold larger than that of individual semiconductor. Moreover, the nanohybrids exhibit excellent photostability after 5 cycles testing in both reaction systems. The morphology, crystal structure and composition for Ti3C2/In4SnS8 remain unaltered after photoreaction. A comprehensive analysis including trapping agents and atmosphere experiments as well as electron paramagnetic resonance demonstrates that the H2O2 evolution pathway consists of two channels:a two-step successive 1e- oxygen reduction reaction and a one-step 2e- water oxidation reaction. This work may provide a viable protocol for designing efficient and multifunctional photocatalytic systems for solar-to-chemical energy conversion.
Artificial photosynthesis is an appealing approach for generating hydrogen peroxide (H2O2) from H2O and O2 with solar energy as the sole energy input. However, the current catalyst systems commonly face challenges such as the limited optical absorption, poor electron-hole pair separation efficiency, and restricted surface reactivity, which hinders the overall photoactivity. Here, we immobilize cubic-phase ultrathin In4SnS8 nanosheets (Eg=2.16 eV) with thickness of 5-10 nm on the surface of few-layer Ti3C2 to develop a sandwich-like hierarchical structure of Ti3C2/In4SnS8 nanohybrid via in situ hydrothermal strategy. The enlarged interfacial area and close contact between Ti3C2 and In4SnS8 benefit for carrier transportation among nanohybrids. Characterization through X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) corroborates the successful construction of Ti3C2/In4SnS8 nanostructures. Band structures investigation including valence band maximum and Mott-Schottky plots reveals the formation of Schottky junction in this 2D/2D heterostructure, that favors for ultrafast charge carrier separation and transportation from In4SnS8 to Ti3C2 and preventing the electrons backflow from Ti3C2 to In4SnS8. Photoluminescene analysis and photo/electrochemical measurements prove that the combination of Ti3C2 and In4SnS8 accelerates the transportation of photoexcited electron-hole pairs and efficiently suppresses charge carrier recombination. Unsurprisingly, 7 wt% Ti3C2/In4SnS8 catalysts exhibit the highest visible-light-driven photoreactivity with H2O2 production rates of 1.998 μmol·L-1·min-1 that is 2.2 times larger than that of single In4SnS8. Additionally, Ti3C2/In4SnS8 demonstrates a multifunctional capability in Cr(VI) reduction with the greatest reaction rates of 19.8×10-3 min-1 that is almost 4-fold larger than that of individual semiconductor. Moreover, the nanohybrids exhibit excellent photostability after 5 cycles testing in both reaction systems. The morphology, crystal structure and composition for Ti3C2/In4SnS8 remain unaltered after photoreaction. A comprehensive analysis including trapping agents and atmosphere experiments as well as electron paramagnetic resonance demonstrates that the H2O2 evolution pathway consists of two channels:a two-step successive 1e- oxygen reduction reaction and a one-step 2e- water oxidation reaction. This work may provide a viable protocol for designing efficient and multifunctional photocatalytic systems for solar-to-chemical energy conversion.
2024, 40(10): 230903
doi: 10.3866/PKU.WHXB202309031
Abstract:
In the pursuit of efficient photocatalytic carbon dioxide (CO2) conversion, the use of artificial semiconductors powered by solar energy offers great potential for simulating natural carbon cycling. However, the efficiency of photocatalytic CO2 conversion remains suboptimal, primarily due to inadequate separation of photogenerated charges, which hinders the performance of semiconductor-based CO2 reduction. Consequently, recent research efforts have focused on identifying ideal materials for CO2 photocatalytic conversion. Among the candidate materials, the structure of Bi2MoO6 consists of alternating layers of (Bi2O2)2+ and perovskite-like (MoO4)2- layers with shared oxygen atoms between them. This inherent charge distribution within Bi2MoO6 creates an inhomogeneous electric field, facilitating the efficient separation of photogenerated charge carriers. The morphology and structure of a catalyst significantly influence the rate of recombination of photogenerated charge carriers. Research has shown that ultrathin Bi2MoO6 nanosheets, compared to other 2D and 3D structures of Bi2MoO6 materials, possess longer fluorescence lifetimes, providing more opportunities for the separation of photogenerated charge carriers. However, Bi2MoO6 still exhibits relatively low catalytic efficiency due to its insufficiently negative conduction band position (ranging between -0.2 and -0.4 V). To address this limitation, a viable strategy is to load a semiconductor with a more negatively positioned conduction band onto Bi2MoO6, creating an S-scheme heterojunction. In this study, Bi2MoO6 nanosheets were synthesized through a hydrothermal method, and simultaneously, CeO2 nanoparticles were grown on their surfaces, forming an S-scheme heterojunction modified with Ce3+/Ce4+ ion bridges. Time-resolved photoluminescence (TRPL) and photoelectrochemical tests demonstrated the enhanced charge separation effect of this heterojunction. In situ X-ray photoelectron spectroscopy (In situ XPS) analysis and theoretical calculations further confirmed that photogenerated electrons follow an S-scheme mechanism, transferring from Bi2MoO6 to CeO2. Experimental results revealed that the photocatalytic CO2 reduction efficiencies of CeO2/Bi2MoO6, Bi2MoO6, and CeO2 were 65.3, 14.8, and 1.2 μmol·g-1·h-1, respectively. Compared to pure Bi2MoO6, the catalytic efficiency of the CeO2/Bi2MoO6 composite catalyst for CO2 photocatalytic reduction to CO improved by a factor of 3.12. This enhancement in photocatalytic CO2 conversion performance can be attributed to the synergistic interaction between the S-scheme heterojunction and Ce3+/Ce4+ ion bridging, resulting in enhanced light absorption, efficient charge separation, and redox capabilities of the composite catalyst. This study offers valuable insights into the rational design and construction of novel S-scheme heterojunction photocatalysts.
In the pursuit of efficient photocatalytic carbon dioxide (CO2) conversion, the use of artificial semiconductors powered by solar energy offers great potential for simulating natural carbon cycling. However, the efficiency of photocatalytic CO2 conversion remains suboptimal, primarily due to inadequate separation of photogenerated charges, which hinders the performance of semiconductor-based CO2 reduction. Consequently, recent research efforts have focused on identifying ideal materials for CO2 photocatalytic conversion. Among the candidate materials, the structure of Bi2MoO6 consists of alternating layers of (Bi2O2)2+ and perovskite-like (MoO4)2- layers with shared oxygen atoms between them. This inherent charge distribution within Bi2MoO6 creates an inhomogeneous electric field, facilitating the efficient separation of photogenerated charge carriers. The morphology and structure of a catalyst significantly influence the rate of recombination of photogenerated charge carriers. Research has shown that ultrathin Bi2MoO6 nanosheets, compared to other 2D and 3D structures of Bi2MoO6 materials, possess longer fluorescence lifetimes, providing more opportunities for the separation of photogenerated charge carriers. However, Bi2MoO6 still exhibits relatively low catalytic efficiency due to its insufficiently negative conduction band position (ranging between -0.2 and -0.4 V). To address this limitation, a viable strategy is to load a semiconductor with a more negatively positioned conduction band onto Bi2MoO6, creating an S-scheme heterojunction. In this study, Bi2MoO6 nanosheets were synthesized through a hydrothermal method, and simultaneously, CeO2 nanoparticles were grown on their surfaces, forming an S-scheme heterojunction modified with Ce3+/Ce4+ ion bridges. Time-resolved photoluminescence (TRPL) and photoelectrochemical tests demonstrated the enhanced charge separation effect of this heterojunction. In situ X-ray photoelectron spectroscopy (In situ XPS) analysis and theoretical calculations further confirmed that photogenerated electrons follow an S-scheme mechanism, transferring from Bi2MoO6 to CeO2. Experimental results revealed that the photocatalytic CO2 reduction efficiencies of CeO2/Bi2MoO6, Bi2MoO6, and CeO2 were 65.3, 14.8, and 1.2 μmol·g-1·h-1, respectively. Compared to pure Bi2MoO6, the catalytic efficiency of the CeO2/Bi2MoO6 composite catalyst for CO2 photocatalytic reduction to CO improved by a factor of 3.12. This enhancement in photocatalytic CO2 conversion performance can be attributed to the synergistic interaction between the S-scheme heterojunction and Ce3+/Ce4+ ion bridging, resulting in enhanced light absorption, efficient charge separation, and redox capabilities of the composite catalyst. This study offers valuable insights into the rational design and construction of novel S-scheme heterojunction photocatalysts.
2024, 40(10): 231001
doi: 10.3866/PKU.WHXB202310013
Abstract:
The escalating presence of pharmaceutical antibiotics in natural water poses an overwhelming threat to the sustainable development of society. Photocatalysis technology stands out as a promising and cutting-edge environmental purification alternative. C3N5, identified as a distinctive nonprecious nonmetal photocatalyst, holds potential for environmental protection. However, challenges persist originating from the sluggish photoreaction kinetics and severe photo-carrier reunion. Currently, the design of a special S-scheme photosystem proves to be a reliable strategy for obtaining outstanding photocatalysts. In this context, a plasmonic S-scheme photosystem involving Ag/Ag3PO4/C3N5 was developed through a feasible route. The compactly connected 0D/0D/2D Ag/Ag3PO4/C3N5 heterostructure, benefitting from the synergy between the plasmonic effect and the S-scheme junction, facilitates the efficient utilization of appreciably reinforced sunlight absorption, effective photo-carrier disassociation, and notable photoredox capacity. Consequently, this system generates ·OH and ·O2- effectively. Ag/Ag3PO4/C3N5 demonstrates a superb photocatalytic levofloxacin eradication rate of 0.0362 min-1, marking a substantial advancement of 24.8, 1.1, and 0.7 folds compared to C3N5, Ag3PO4, and Ag3PO4/C3N5, respectively. Impressively, Ag/Ag3PO4/C3N5 delivers remarkable anti-interference performance and reusability. This achievement signifies a significant step toward developing potent C3N5-involved photosystems for environmental purification.
The escalating presence of pharmaceutical antibiotics in natural water poses an overwhelming threat to the sustainable development of society. Photocatalysis technology stands out as a promising and cutting-edge environmental purification alternative. C3N5, identified as a distinctive nonprecious nonmetal photocatalyst, holds potential for environmental protection. However, challenges persist originating from the sluggish photoreaction kinetics and severe photo-carrier reunion. Currently, the design of a special S-scheme photosystem proves to be a reliable strategy for obtaining outstanding photocatalysts. In this context, a plasmonic S-scheme photosystem involving Ag/Ag3PO4/C3N5 was developed through a feasible route. The compactly connected 0D/0D/2D Ag/Ag3PO4/C3N5 heterostructure, benefitting from the synergy between the plasmonic effect and the S-scheme junction, facilitates the efficient utilization of appreciably reinforced sunlight absorption, effective photo-carrier disassociation, and notable photoredox capacity. Consequently, this system generates ·OH and ·O2- effectively. Ag/Ag3PO4/C3N5 demonstrates a superb photocatalytic levofloxacin eradication rate of 0.0362 min-1, marking a substantial advancement of 24.8, 1.1, and 0.7 folds compared to C3N5, Ag3PO4, and Ag3PO4/C3N5, respectively. Impressively, Ag/Ag3PO4/C3N5 delivers remarkable anti-interference performance and reusability. This achievement signifies a significant step toward developing potent C3N5-involved photosystems for environmental purification.
2024, 40(10): 231101
doi: 10.3866/PKU.WHXB202311016
Abstract:
Directional electron transfer is an appealing strategy for harnessing photogenerated charge separation kinetics. Herein, a novel 2D/1D SnNb2O6/nitrogen-enriched C3N5 S-scheme heterojunction with strong internal electric field (IEF) and dipole field (DF) is designed through in situ growth of C3N5 nanorods on SnNb2O6 nanosheets. The IEF generated at the interface via the formation of the S-scheme heterojunction induces directional charge transfer from SnNb2O6 to C3N5. Simultaneously, the DF within C3N5 provides the impetus to guide photo-excited electrons to the active sites. Consequently, the synergistic effects of IEF and DF facilitate swift directional electron transfer. The optimized SnNb2O6/C3N5 heterojunction demonstrates a remarkable H2 production rate of 1090.0 μmol·g-1·h-1 with continuous release of H2 bubbles. This performance surpasses that of SnNb2O6 and C3N5 by 38.8 and 10.7 times, respectively. Additionally, the SnNb2O6/C3N5 heterojunction exhibits superior activity in the removal of Rhodamine B, tetracycline, and Cr(VI). Based on electron paramagnetic resonance (EPR), time-resolved photoluminescence (TPRL) and density functional theory (DFT) calculations, etc., the directional charge transfer mechanism was systematically explored. The research furnishes a plausible approach to construct effective heterojunction photocatalysts for applications in energy and environmental domains.
Directional electron transfer is an appealing strategy for harnessing photogenerated charge separation kinetics. Herein, a novel 2D/1D SnNb2O6/nitrogen-enriched C3N5 S-scheme heterojunction with strong internal electric field (IEF) and dipole field (DF) is designed through in situ growth of C3N5 nanorods on SnNb2O6 nanosheets. The IEF generated at the interface via the formation of the S-scheme heterojunction induces directional charge transfer from SnNb2O6 to C3N5. Simultaneously, the DF within C3N5 provides the impetus to guide photo-excited electrons to the active sites. Consequently, the synergistic effects of IEF and DF facilitate swift directional electron transfer. The optimized SnNb2O6/C3N5 heterojunction demonstrates a remarkable H2 production rate of 1090.0 μmol·g-1·h-1 with continuous release of H2 bubbles. This performance surpasses that of SnNb2O6 and C3N5 by 38.8 and 10.7 times, respectively. Additionally, the SnNb2O6/C3N5 heterojunction exhibits superior activity in the removal of Rhodamine B, tetracycline, and Cr(VI). Based on electron paramagnetic resonance (EPR), time-resolved photoluminescence (TPRL) and density functional theory (DFT) calculations, etc., the directional charge transfer mechanism was systematically explored. The research furnishes a plausible approach to construct effective heterojunction photocatalysts for applications in energy and environmental domains.
2024, 40(10): 231200
doi: 10.3866/PKU.WHXB202312007
Abstract:
Transitional metal oxyhydroxides have been demonstrated to be the reliable cocatalysts for water oxidation reaction. However, their insufficient adsorption ability for H2O and its intermediate products during water oxidation greatly restricts the improvement of water oxidation rate. In this study, a spontaneously improved adsorption of H2O and its intermediates on the electron-deficient Mn(3+δ)+ of MnOOH cocatalyst can greatly promote the rapid water oxidation to realize the efficient photocatalytic H2O2 production in a pure water system. In this case, amorphous MnOOH is selectively deposited on the (110) facet of AuPd-modified single-crystal BiVO4 photocatalyst via the directionally photoinduced oxidation approach to produce AuPd/BiVO4/MnOOH photocatalyst. Photocatalytic experiments exhibit that the as-prepared AuPd/BiVO4/MnOOH (0.5%) photocatalyst obtains the boosted H2O2-evolution rate of 214 μmol·L-1 as well as exhibits an outstanding stability and reproducibility. Density functional theory calculations and X-ray photoelectron spectroscopy (XPS) characterization reveal that the free electrons of MnOOH can effectively transfer to BiVO4 to induce the generation of electron-deficient Mn sites (Mn(3+δ)+), which spontaneously promotes the adsorption of H2O and its intermediates for enhancing 4-electron water oxidation reaction, resulting in an efficient H2O2 production. The present work about the strong interaction between cocatalyst and bulk catalyst provides a fresh idea for the rational design of highly efficient catalytic materials.
Transitional metal oxyhydroxides have been demonstrated to be the reliable cocatalysts for water oxidation reaction. However, their insufficient adsorption ability for H2O and its intermediate products during water oxidation greatly restricts the improvement of water oxidation rate. In this study, a spontaneously improved adsorption of H2O and its intermediates on the electron-deficient Mn(3+δ)+ of MnOOH cocatalyst can greatly promote the rapid water oxidation to realize the efficient photocatalytic H2O2 production in a pure water system. In this case, amorphous MnOOH is selectively deposited on the (110) facet of AuPd-modified single-crystal BiVO4 photocatalyst via the directionally photoinduced oxidation approach to produce AuPd/BiVO4/MnOOH photocatalyst. Photocatalytic experiments exhibit that the as-prepared AuPd/BiVO4/MnOOH (0.5%) photocatalyst obtains the boosted H2O2-evolution rate of 214 μmol·L-1 as well as exhibits an outstanding stability and reproducibility. Density functional theory calculations and X-ray photoelectron spectroscopy (XPS) characterization reveal that the free electrons of MnOOH can effectively transfer to BiVO4 to induce the generation of electron-deficient Mn sites (Mn(3+δ)+), which spontaneously promotes the adsorption of H2O and its intermediates for enhancing 4-electron water oxidation reaction, resulting in an efficient H2O2 production. The present work about the strong interaction between cocatalyst and bulk catalyst provides a fresh idea for the rational design of highly efficient catalytic materials.
2024, 40(10): 231201
doi: 10.3866/PKU.WHXB202312010
Abstract:
Cu-Graphdiyne and CoNiWO4 were synthesized by organic and hydrothermal methods, respectively. The establishment of an S-scheme heterojunction between Cu-Graphdiyne and CoNiWO4 was achieved by interface engineering design. The efficient separation and transfer of photogenerated carriers are facilitated by the synergistic effect of the built-in electric field and band bending, while maintaining the strong redox capacity of the catalysts. The introduction of Cu-Graphdiyne effectively enhances the photo absorption capacity and conductivity of the composite catalyst, and significantly suppresses the recombination of photogenerated carriers. The unique two-dimensional planar network structure of Cu-Graphdiyne provides abundant active sites for photocatalytic processes, thereby facilitating the photocatalytic reaction. Density functional theory (DFT) calculations demonstrate that hot electrons generated by surface plasmon resonance effects of Cu will transfer to Graphdiyne to promote hydrogen evolution reaction. This study offers insights into potential applications of Cu-Graphdiyne and nickel-cobalt based catalysts in photocatalytic hydrogen evolution.
Cu-Graphdiyne and CoNiWO4 were synthesized by organic and hydrothermal methods, respectively. The establishment of an S-scheme heterojunction between Cu-Graphdiyne and CoNiWO4 was achieved by interface engineering design. The efficient separation and transfer of photogenerated carriers are facilitated by the synergistic effect of the built-in electric field and band bending, while maintaining the strong redox capacity of the catalysts. The introduction of Cu-Graphdiyne effectively enhances the photo absorption capacity and conductivity of the composite catalyst, and significantly suppresses the recombination of photogenerated carriers. The unique two-dimensional planar network structure of Cu-Graphdiyne provides abundant active sites for photocatalytic processes, thereby facilitating the photocatalytic reaction. Density functional theory (DFT) calculations demonstrate that hot electrons generated by surface plasmon resonance effects of Cu will transfer to Graphdiyne to promote hydrogen evolution reaction. This study offers insights into potential applications of Cu-Graphdiyne and nickel-cobalt based catalysts in photocatalytic hydrogen evolution.
2024, 40(10): 231201
doi: 10.3866/PKU.WHXB202312014
Abstract:
Covalent organic frameworks (COFs) represent a kind of novel crystalline porous organic substances with extended π-conjugation framework and tunable structures, which display great promise in photocatalysis. However, unadorned COFs suffer from sluggish reaction kinetics, and a cocatalyst is essentially needed to reduce the activation barrier toward specific surface reaction and accelerate reaction kinetics. In this work, bimetallic alloys serving as co-catalysts were decorated on COFs to enhance the photocatalytic hydrogen evolution performance. By precisely-tuning the ratio of AuCu alloy, the resultant Au1Cu5/COF-TpPa displays the highest photocatalytic hydrogen generation rate (8.24 mmol·g-1·h-1), even surpassing the Pt modified COF-TpPa (6.51 mmol·h-1·g-1). According to the systematic characterizations and theoretical calculation, Au1Cu5/COF-TpPa exhibits the significantly enhanced charge carrier separation efficiency and reduced H* formation energy barrier, thus possessing high photocatalytic performance. This work affords a valuable approach to advancing COF-based photocatalysts by employing bimetallic alloy cocatalysts.
Covalent organic frameworks (COFs) represent a kind of novel crystalline porous organic substances with extended π-conjugation framework and tunable structures, which display great promise in photocatalysis. However, unadorned COFs suffer from sluggish reaction kinetics, and a cocatalyst is essentially needed to reduce the activation barrier toward specific surface reaction and accelerate reaction kinetics. In this work, bimetallic alloys serving as co-catalysts were decorated on COFs to enhance the photocatalytic hydrogen evolution performance. By precisely-tuning the ratio of AuCu alloy, the resultant Au1Cu5/COF-TpPa displays the highest photocatalytic hydrogen generation rate (8.24 mmol·g-1·h-1), even surpassing the Pt modified COF-TpPa (6.51 mmol·h-1·g-1). According to the systematic characterizations and theoretical calculation, Au1Cu5/COF-TpPa exhibits the significantly enhanced charge carrier separation efficiency and reduced H* formation energy barrier, thus possessing high photocatalytic performance. This work affords a valuable approach to advancing COF-based photocatalysts by employing bimetallic alloy cocatalysts.
2024, 40(10): 230902
doi: 10.3866/PKU.WHXB202309028
Abstract:
Rechargeable lithium-ion batteries (LIBs) have garnered global attention as a prominent solution for storing intermittent renewable energy, addressing energy scarcity, and mitigating environmental pollution. In the previous century, Sony introduced the "lithium-ion battery" concept, heralding a new era for LIBs and effectively bringing them into commercial use. The initial commercially available LIBs utilized lithium cobalt oxide as the cathode material and graphite as the anode material. Capitalizing on their attributes encompassing elevated energy density, substantial specific capacity, portability, and ecological compatibility, LIBs have secured substantial market share throughout the commercialization trajectory. Their commercial viability and scope have been markedly enhanced through the continuous advancement of LIBs' cathode materials and innovative implementations encompassing battery design, assembly, and thermal management. In recent years, the rapid expansion of sectors such as cellular phones and new energy vehicles, coupled with the drive towards "carbon peaking" and "carbon neutrality," has propelled the robust growth of the LIBs sector, which has resulted in widespread adoption across diverse industrial domains and daily applications spanning road transportation, materials, chemicals, and information technology. However, the swift proliferation of the LIBs industry has incited an influx of end-of-life (EOL) batteries, which pose risks of flammability, explosiveness, and the presence of toxic and hazardous elements, including fluorides. These aspects collectively pose a formidable environmental and human health hazard, warranting urgent and harmless disposal measures. Simultaneously, EOL LIBs are rich reservoirs of resources like lithium, nickel, cobalt, and manganese, boasting metal contents in cathode waste that significantly exceed those found in their natural mineral counterparts, presenting a substantial opportunity for resource reclamation. Therefore, extracting valuable metals from LIBs cathode waste simultaneously addresses critical environmental and human health concerns linked to improper EOL LIBs disposal while playing a pivotal role in mitigating metal resource shortages. This dual-purpose endeavor aligns with the overarching goal of promoting sustainable resource circulation. The recovery of LIBs cathode materials is a central topic of global research discussion. This study comprehensively overviews valuable metal extraction from LIBs cathode waste using hydrometallurgical methodologies. It delves deeply into diverse approaches encompassing inorganic, organic, and deep eutectic solvents (DESs), scrutinizing environmental, technical, and industrial feasibilities. The objective is to optimize extraction techniques and mitigate their environmental impact. Furthermore, this paper meticulously discusses the utilization of environmentally friendly reducing agents like green biomass waste, coupled with the efficient and eco-conscious EOL LIBs internal cycle mechanical activation technology, to enhance the leaching of valuable metals from cathode waste. This inquiry culminates in identifying potential research avenues and challenges within the EOL LIBs recycling process.
Rechargeable lithium-ion batteries (LIBs) have garnered global attention as a prominent solution for storing intermittent renewable energy, addressing energy scarcity, and mitigating environmental pollution. In the previous century, Sony introduced the "lithium-ion battery" concept, heralding a new era for LIBs and effectively bringing them into commercial use. The initial commercially available LIBs utilized lithium cobalt oxide as the cathode material and graphite as the anode material. Capitalizing on their attributes encompassing elevated energy density, substantial specific capacity, portability, and ecological compatibility, LIBs have secured substantial market share throughout the commercialization trajectory. Their commercial viability and scope have been markedly enhanced through the continuous advancement of LIBs' cathode materials and innovative implementations encompassing battery design, assembly, and thermal management. In recent years, the rapid expansion of sectors such as cellular phones and new energy vehicles, coupled with the drive towards "carbon peaking" and "carbon neutrality," has propelled the robust growth of the LIBs sector, which has resulted in widespread adoption across diverse industrial domains and daily applications spanning road transportation, materials, chemicals, and information technology. However, the swift proliferation of the LIBs industry has incited an influx of end-of-life (EOL) batteries, which pose risks of flammability, explosiveness, and the presence of toxic and hazardous elements, including fluorides. These aspects collectively pose a formidable environmental and human health hazard, warranting urgent and harmless disposal measures. Simultaneously, EOL LIBs are rich reservoirs of resources like lithium, nickel, cobalt, and manganese, boasting metal contents in cathode waste that significantly exceed those found in their natural mineral counterparts, presenting a substantial opportunity for resource reclamation. Therefore, extracting valuable metals from LIBs cathode waste simultaneously addresses critical environmental and human health concerns linked to improper EOL LIBs disposal while playing a pivotal role in mitigating metal resource shortages. This dual-purpose endeavor aligns with the overarching goal of promoting sustainable resource circulation. The recovery of LIBs cathode materials is a central topic of global research discussion. This study comprehensively overviews valuable metal extraction from LIBs cathode waste using hydrometallurgical methodologies. It delves deeply into diverse approaches encompassing inorganic, organic, and deep eutectic solvents (DESs), scrutinizing environmental, technical, and industrial feasibilities. The objective is to optimize extraction techniques and mitigate their environmental impact. Furthermore, this paper meticulously discusses the utilization of environmentally friendly reducing agents like green biomass waste, coupled with the efficient and eco-conscious EOL LIBs internal cycle mechanical activation technology, to enhance the leaching of valuable metals from cathode waste. This inquiry culminates in identifying potential research avenues and challenges within the EOL LIBs recycling process.
2024, 40(10): 231003
doi: 10.3866/PKU.WHXB202310034
Abstract:
Non-renewable energy sources such as fossil fuels are increasingly depleted. In order to cope with the potential energy crisis, it is urgent to develop clean and efficient renewable energy sources. Advanced energy storage technology based on electrical energy holds critical significance to the sustainable and steady development of human society. Aqueous rechargeable batteries are a kind of promising electrochemical energy storage devices. Zinc-ion batteries (ZIBs) are gaining increasing popularity due to their safety, sustainability, cost-effectiveness and high energy density, positioning them as potential successors to current Lithium-ion batteries (LIBs) with a high degree of commercialization. The extraordinary mechanical flexibility and excellent electrochemical performance exhibited by ZIBs holds great significance in advancing the development of flexible and wearable batteries. Manganese-based oxides with large channel size possess the characteristics of high theoretical capacity, various oxidation states (including +2, +3, +4) and low cost, which are commonly employed as cathode materials for AZIBs. Nevertheless, the electrochemical performance of current manganese-based ZIBs is not satisfactory, facing the challenges of metal dissolution, material structure instability, notably a strong electrostatic interaction exhibited by divalent Zn2+ ions in the host structure resulting in slow transmission kinetics. These challenges contribute to low cycle stability of the battery, impeding practical application and the progression of ZIBs. To solve these problems, diverse structural engineering strategies including defect engineering have been exploited, which can effectively improve the transport kinetics of zinc ions. From the perspective of enhancing the performance of the material itself, interlayer intercalation and other measures can be taken to better the microstructure or morphology of manganese-based materials. By improving the electrical conductivity of the material and enhancing ionic bonding, the structural stability and electrochemical performance of the material can be effectively improved. And from the angle of battery design, in order to improve the stability of the electrode-electrolyte interface, the electrolyte is optimized, or a fresh preparation method different from the conventional slurry coating process is adopted, which is also a promising method to design a new electrode without binder and the electrode components can still be evenly distributed. This review provides an overview of Zinc-ion storage mechanisms:the reversible Zn2+ insertion/extraction; the reversible interposition and deintercalation of Zn2+ and H+; the chemical conversion reactions, and the mechanism of dissolution-deposition reaction. Furthermore, the challenges faced by manganese-based cathode materials are clarified, and the optimization strategies to improve their electrochemical performance by increasing active sites, reducing solid-state diffusion energy barriers, inhibiting the dissolution of active substances, and improving material stability are highlighted. Finally, the practical application and potential of ZIBs assembled by manganese-based cathode materials in biomedical equipment and other electronic devices are also discussed.
Non-renewable energy sources such as fossil fuels are increasingly depleted. In order to cope with the potential energy crisis, it is urgent to develop clean and efficient renewable energy sources. Advanced energy storage technology based on electrical energy holds critical significance to the sustainable and steady development of human society. Aqueous rechargeable batteries are a kind of promising electrochemical energy storage devices. Zinc-ion batteries (ZIBs) are gaining increasing popularity due to their safety, sustainability, cost-effectiveness and high energy density, positioning them as potential successors to current Lithium-ion batteries (LIBs) with a high degree of commercialization. The extraordinary mechanical flexibility and excellent electrochemical performance exhibited by ZIBs holds great significance in advancing the development of flexible and wearable batteries. Manganese-based oxides with large channel size possess the characteristics of high theoretical capacity, various oxidation states (including +2, +3, +4) and low cost, which are commonly employed as cathode materials for AZIBs. Nevertheless, the electrochemical performance of current manganese-based ZIBs is not satisfactory, facing the challenges of metal dissolution, material structure instability, notably a strong electrostatic interaction exhibited by divalent Zn2+ ions in the host structure resulting in slow transmission kinetics. These challenges contribute to low cycle stability of the battery, impeding practical application and the progression of ZIBs. To solve these problems, diverse structural engineering strategies including defect engineering have been exploited, which can effectively improve the transport kinetics of zinc ions. From the perspective of enhancing the performance of the material itself, interlayer intercalation and other measures can be taken to better the microstructure or morphology of manganese-based materials. By improving the electrical conductivity of the material and enhancing ionic bonding, the structural stability and electrochemical performance of the material can be effectively improved. And from the angle of battery design, in order to improve the stability of the electrode-electrolyte interface, the electrolyte is optimized, or a fresh preparation method different from the conventional slurry coating process is adopted, which is also a promising method to design a new electrode without binder and the electrode components can still be evenly distributed. This review provides an overview of Zinc-ion storage mechanisms:the reversible Zn2+ insertion/extraction; the reversible interposition and deintercalation of Zn2+ and H+; the chemical conversion reactions, and the mechanism of dissolution-deposition reaction. Furthermore, the challenges faced by manganese-based cathode materials are clarified, and the optimization strategies to improve their electrochemical performance by increasing active sites, reducing solid-state diffusion energy barriers, inhibiting the dissolution of active substances, and improving material stability are highlighted. Finally, the practical application and potential of ZIBs assembled by manganese-based cathode materials in biomedical equipment and other electronic devices are also discussed.
2024, 40(10): 231103
doi: 10.3866/PKU.WHXB202311030
Abstract:
Highly coveted for their exceptional energy density, extended cycle life, impressive rate capability, and thermal stability, lithium-ion batteries (LIBs) stand out as the optimal power sources for real-world applications, ranging from portable electronics to electric vehicles (EVs). In this context, coaxial electrospinning has emerged as a compelling technique for fabricating nanofiber materials endowed with properties ideally suited for LIBs. These properties include a high specific surface area, exceptional porosity, a substantial aspect ratio, and facile surface modification. This comprehensive review encapsulates the fundamental principles, practical applications, and recent strides in coaxial electrospinning, particularly in the preparation of crucial LIB components such as cathodes, anodes, and separators. The intricate relationships between the micro/nanostructures of coaxially electrospun fiber materials and their resultant battery performances are meticulously examined. Additionally, the review outlines future directions and underscores the challenges inherent in advancing the field of coaxial electrospinning for LIBs.
Highly coveted for their exceptional energy density, extended cycle life, impressive rate capability, and thermal stability, lithium-ion batteries (LIBs) stand out as the optimal power sources for real-world applications, ranging from portable electronics to electric vehicles (EVs). In this context, coaxial electrospinning has emerged as a compelling technique for fabricating nanofiber materials endowed with properties ideally suited for LIBs. These properties include a high specific surface area, exceptional porosity, a substantial aspect ratio, and facile surface modification. This comprehensive review encapsulates the fundamental principles, practical applications, and recent strides in coaxial electrospinning, particularly in the preparation of crucial LIB components such as cathodes, anodes, and separators. The intricate relationships between the micro/nanostructures of coaxially electrospun fiber materials and their resultant battery performances are meticulously examined. Additionally, the review outlines future directions and underscores the challenges inherent in advancing the field of coaxial electrospinning for LIBs.
2024, 40(10): 231202
doi: 10.3866/PKU.WHXB202312024
Abstract:
