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2025 Volume 41 Issue 2
2025, 41(2):
Abstract:
2025, 41(2): 100010
doi: 10.3866/PKU.WHXB202309041
Abstract:
Machine learning (ML) is progressively revealing notable advantages in chemical synthesis. However, the limited output of experimental data from traditional methods poses a bottleneck, impeding the widespread adoption of machine learning. Data from literature often leads to overly optimistic predictions, and obtaining thousands of experimental data points through experiments remains a substantial challenge. Using a small dataset of experimental data, we illustrated that machine learning algorithms can reliably predict the conversion rate of amide bond synthesis. We gathered hundreds of experimental data points for 9 aromatic amines and 12 organic acids using various coupling reagents and solvents in a 96-well plate high-throughput experimental setup. Subsequently, we derived 76 feature molecular descriptors from quantum chemical calculations and utilized them as inputs for training the machine learning model. Despite the inherent limitation of low data volume, the random forest algorithm demonstrated outstanding predictive performance (R2 > 0.95). Through comprehensive analysis of the reaction process employing importance analysis, shapley additive explanations (SHAP), and accumulated local effects (ALE) methods, we delved into the important factors influencing the reaction conversion rate. In predicting the conversion rate of unknown aromatic amine molecules, we discovered that incorporating a small amount of unknown molecule-related reaction data into the training set effectively enhances the model’s predictive performance, even with a small dataset. By comparing models trained on different molecular descriptors such as density functional theory (DFT) and one-hot encoding, we validated the efficacy of adjusting the training set to improve prediction results. This study utilized a multitude of chemically meaningful feature descriptors and achieved more effective prediction results through multidimensional data analysis, offering valuable insights for machine learning-assisted chemical synthesis research in small datasets. In the near future, machine learning is poised to drive the intelligent development of organic chemistry.
Machine learning (ML) is progressively revealing notable advantages in chemical synthesis. However, the limited output of experimental data from traditional methods poses a bottleneck, impeding the widespread adoption of machine learning. Data from literature often leads to overly optimistic predictions, and obtaining thousands of experimental data points through experiments remains a substantial challenge. Using a small dataset of experimental data, we illustrated that machine learning algorithms can reliably predict the conversion rate of amide bond synthesis. We gathered hundreds of experimental data points for 9 aromatic amines and 12 organic acids using various coupling reagents and solvents in a 96-well plate high-throughput experimental setup. Subsequently, we derived 76 feature molecular descriptors from quantum chemical calculations and utilized them as inputs for training the machine learning model. Despite the inherent limitation of low data volume, the random forest algorithm demonstrated outstanding predictive performance (R2 > 0.95). Through comprehensive analysis of the reaction process employing importance analysis, shapley additive explanations (SHAP), and accumulated local effects (ALE) methods, we delved into the important factors influencing the reaction conversion rate. In predicting the conversion rate of unknown aromatic amine molecules, we discovered that incorporating a small amount of unknown molecule-related reaction data into the training set effectively enhances the model’s predictive performance, even with a small dataset. By comparing models trained on different molecular descriptors such as density functional theory (DFT) and one-hot encoding, we validated the efficacy of adjusting the training set to improve prediction results. This study utilized a multitude of chemically meaningful feature descriptors and achieved more effective prediction results through multidimensional data analysis, offering valuable insights for machine learning-assisted chemical synthesis research in small datasets. In the near future, machine learning is poised to drive the intelligent development of organic chemistry.
2025, 41(2): 100012
doi: 10.3866/PKU.WHXB202309027
Abstract:
Excited-state intramolecular proton transfer (ESIPT) is a fundamental photoreaction of significant importance in both chemical and biological systems. This phenomenon typically occurs in chromophores featuring intramolecular hydrogen bonding. Among the molecules undergoing ESIPT, 3-hydroxyflavone derivatives (3-HFs) have garnered significant attention due to their natural origins and environmentally responsive fluorescence properties. A particular 3-HF compound, 4'-N,N-diethylamino-3-hydroxybenzoflavone (D-HBF), distinguished by its extended π-system and red-shifted electronic absorption, has recently been identified as a potent fluorescent probe highly sensitive to changes in environmental polarity. In this study, we systematically explored the ESIPT reaction mechanism of D-HBF in three aprotic solvents: cyclohexane, diethyl ether, and tetrahydrofuran, each possessing varying polarities. Our investigation involved a combination of spectroscopic and theoretical methods. In all three solvents, we observed the characteristic dual emission bands associated with ESIPT, with the intensity ratio of these bands being influenced by the solvent. As solvent polarity increased, we noted a decrease in the rates of both the forward and reverse proton transfer (PT) reactions based on our analysis of fluorescent kinetics. However, the reverse PT was favored. Through density functional theory (DFT) and time-dependent DFT (TDDFT) calculations of bond lengths and bond angles of the intramolecular hydrogen bond in these solvents, we confirmed that the ESIPT reaction in D-HBF is driven by the strengthening of the excited-state hydrogen bond. Notably, upon increasing solvent polarity, the intramolecular hydrogen bonds in the excited N* state weakened, as evidenced by the up-shifted IR absorption frequency of the O―H stretching mode in the S1 state. Electron intensity analysis of frontier orbitals revealed characteristic intramolecular charge transfer (ICT) occurring in D-HBF upon photoexcitation, attributable to the introduction of a strong electron-donating group at the 4' position (4'-N,N-diethylamino-). Calculations of potential energy curves for the S0 and S1 states confirmed that the PT process tends to occur in the S1 state rather than the S0 state, and a more polar solvent generates a more significant potential barrier, hindering the corresponding ESIPT reaction. An analysis of the Gibbs free energy of ESIPT further confirmed that increasing solvent polarity favors the equilibrium shifting toward the N* state. This research lays the foundation for potential future applications of D-HBF as a biological fluorescent probe sensitive to environmental polarity.
Excited-state intramolecular proton transfer (ESIPT) is a fundamental photoreaction of significant importance in both chemical and biological systems. This phenomenon typically occurs in chromophores featuring intramolecular hydrogen bonding. Among the molecules undergoing ESIPT, 3-hydroxyflavone derivatives (3-HFs) have garnered significant attention due to their natural origins and environmentally responsive fluorescence properties. A particular 3-HF compound, 4'-N,N-diethylamino-3-hydroxybenzoflavone (D-HBF), distinguished by its extended π-system and red-shifted electronic absorption, has recently been identified as a potent fluorescent probe highly sensitive to changes in environmental polarity. In this study, we systematically explored the ESIPT reaction mechanism of D-HBF in three aprotic solvents: cyclohexane, diethyl ether, and tetrahydrofuran, each possessing varying polarities. Our investigation involved a combination of spectroscopic and theoretical methods. In all three solvents, we observed the characteristic dual emission bands associated with ESIPT, with the intensity ratio of these bands being influenced by the solvent. As solvent polarity increased, we noted a decrease in the rates of both the forward and reverse proton transfer (PT) reactions based on our analysis of fluorescent kinetics. However, the reverse PT was favored. Through density functional theory (DFT) and time-dependent DFT (TDDFT) calculations of bond lengths and bond angles of the intramolecular hydrogen bond in these solvents, we confirmed that the ESIPT reaction in D-HBF is driven by the strengthening of the excited-state hydrogen bond. Notably, upon increasing solvent polarity, the intramolecular hydrogen bonds in the excited N* state weakened, as evidenced by the up-shifted IR absorption frequency of the O―H stretching mode in the S1 state. Electron intensity analysis of frontier orbitals revealed characteristic intramolecular charge transfer (ICT) occurring in D-HBF upon photoexcitation, attributable to the introduction of a strong electron-donating group at the 4' position (4'-N,N-diethylamino-). Calculations of potential energy curves for the S0 and S1 states confirmed that the PT process tends to occur in the S1 state rather than the S0 state, and a more polar solvent generates a more significant potential barrier, hindering the corresponding ESIPT reaction. An analysis of the Gibbs free energy of ESIPT further confirmed that increasing solvent polarity favors the equilibrium shifting toward the N* state. This research lays the foundation for potential future applications of D-HBF as a biological fluorescent probe sensitive to environmental polarity.
2025, 41(2): 100015
doi: 10.3866/PKU.WHXB202310024
Abstract:
Lithium-based semi-solid flow batteries (LSSFBs) could potentially be applied in large-scale energy storage systems due to their high safety and relatively independent equipment units. However, the electrochemical performance of LSSFBs is limited by the unstable contact between conductive additives and active materials, as well as the poor conductivity of active materials. Therefore, it is necessary to develop semi-solid electrodes with high stability and specific capacity to obtain LSSFBs with satisfied energy density. Herein, carbon-coated SnO2/multi-walled carbon nanotubes (C-SnO2/MWCNTs) composite was designed as the anode material of LSSFBs. In such composite, SnO2 nanoparticles are uniformly distributed on the surface of MWCNTs and coated with carbon layer, which was identified by field-emission scanning electron microscopy, transmission electron microscopy and X-ray diffraction (XRD) results. In general, the traditional SnO2 as active material in electrodes will suffer from volume expansion and collapse of structure, which will decline the cycle life of batteries. In this composite, the nanoparticle structure endows SnO2 with more reaction active sites. Furthermore, MWCNTs and carbon layer can construct a stable conductive network, which enhances the electron transport in SnO2-based electrodes. Simultaneously, MWCNTs and carbon layer also achieve an integrated architecture. Thus, the electron transfer dynamics of SnO2-based electrodes could be improved and their volume expansion is effectively suppressed during charging/discharging process, resulting in improved rate and cycling performance. The coin-type batteries based on C-SnO2/MWCNTs can maintain a discharge capacity of 725 mAh∙g−1 after 100 cycles under a current density of 0.5 A∙g−1. On the contrary, the discharge capacity of the batteries based on bulk SnO2 almost disappears after 100 cycles, which is attributed to the poor conductivity and excessive volume expansion of electrode materials. In addition, the MWCNTs will enhance the suspension stability of the semi-solid electrode. When the mass fraction of the C-SnO2/MWCNTs in the semi-solid electrode is 8.0%, the semi-solid electrode has superior suspension and electron conductivity, as well as suitable viscosity. Furthermore, the lithium storage mechanism of the semi-solid electrode was explored by ex situ XRD and X-ray photoelectron spectroscopy. The results show that, in C-SnO2/MWCNTs composite, SnO2 has a dual Li+ ions storage mechanism involving conversion and alloying reactions. When the flow rate is controlled with 5 mL∙min−1, the conduction network reaches a dynamic balance, and the semi-solid electrode exhibits low charge transfer resistance. These advantages endow the LSSFBs with superior rate and cycling performance. The semi-solid flow batteries could maintain 42.4% of their initial capacity (690.8 mAh∙g−1) after cycling for 962 h at 0.2 mA∙cm−2. This work provides a promising strategy for optimizing the semi-solid electrode of LSSFBs.
Lithium-based semi-solid flow batteries (LSSFBs) could potentially be applied in large-scale energy storage systems due to their high safety and relatively independent equipment units. However, the electrochemical performance of LSSFBs is limited by the unstable contact between conductive additives and active materials, as well as the poor conductivity of active materials. Therefore, it is necessary to develop semi-solid electrodes with high stability and specific capacity to obtain LSSFBs with satisfied energy density. Herein, carbon-coated SnO2/multi-walled carbon nanotubes (C-SnO2/MWCNTs) composite was designed as the anode material of LSSFBs. In such composite, SnO2 nanoparticles are uniformly distributed on the surface of MWCNTs and coated with carbon layer, which was identified by field-emission scanning electron microscopy, transmission electron microscopy and X-ray diffraction (XRD) results. In general, the traditional SnO2 as active material in electrodes will suffer from volume expansion and collapse of structure, which will decline the cycle life of batteries. In this composite, the nanoparticle structure endows SnO2 with more reaction active sites. Furthermore, MWCNTs and carbon layer can construct a stable conductive network, which enhances the electron transport in SnO2-based electrodes. Simultaneously, MWCNTs and carbon layer also achieve an integrated architecture. Thus, the electron transfer dynamics of SnO2-based electrodes could be improved and their volume expansion is effectively suppressed during charging/discharging process, resulting in improved rate and cycling performance. The coin-type batteries based on C-SnO2/MWCNTs can maintain a discharge capacity of 725 mAh∙g−1 after 100 cycles under a current density of 0.5 A∙g−1. On the contrary, the discharge capacity of the batteries based on bulk SnO2 almost disappears after 100 cycles, which is attributed to the poor conductivity and excessive volume expansion of electrode materials. In addition, the MWCNTs will enhance the suspension stability of the semi-solid electrode. When the mass fraction of the C-SnO2/MWCNTs in the semi-solid electrode is 8.0%, the semi-solid electrode has superior suspension and electron conductivity, as well as suitable viscosity. Furthermore, the lithium storage mechanism of the semi-solid electrode was explored by ex situ XRD and X-ray photoelectron spectroscopy. The results show that, in C-SnO2/MWCNTs composite, SnO2 has a dual Li+ ions storage mechanism involving conversion and alloying reactions. When the flow rate is controlled with 5 mL∙min−1, the conduction network reaches a dynamic balance, and the semi-solid electrode exhibits low charge transfer resistance. These advantages endow the LSSFBs with superior rate and cycling performance. The semi-solid flow batteries could maintain 42.4% of their initial capacity (690.8 mAh∙g−1) after cycling for 962 h at 0.2 mA∙cm−2. This work provides a promising strategy for optimizing the semi-solid electrode of LSSFBs.
2025, 41(2): 100016
doi: 10.3866/PKU.WHXB202310029
Abstract:
Two-dimensional (2D) transition-metal dichalcogenides (TMDs) exhibit diverse structures, encompassing a broad spectrum of electronic types ranging from metal, semiconductor, to insulator and topological insulator. They hold immense potential for both Moore and more-than-Moore device applications. Among them, manganese telluride (MnTe), an emerging nonlayered 2D material, has garnered considerable attention due to its exceptional properties and significant application potential in next-generation electronic and optoelectronic devices. However, the controllable synthesis of ultra-thin 2D MnTe remains a great challenge, which hindering the comprehensive exploration of its fundamental properties and potential applications. In this study, we present the synthesis of large-area MnTe nanosheets through chemical vapor deposition growth, showcasing its thickness-dependent properties and device applications. By increasing the growth temperature from 500 to 750 ℃, the MnTe nanosheets’ thickness transitions from thin-layer to a thick flake, the domain size increases from 10 to 125 μm, the morphology changes from triangle to hexagon, culminating in a highly symmetrical round shape. Structural characterization and second harmonic generation measurements reveal that the obtained MnTe nanosheets exhibit high crystallization quality and superior second-order optical nonlinearity. The field effect transistor (FET) constructed with thin-layer MnTe demonstrates a p-type semiconductor characteristic, transitioning to a semimetal feature as the thickness increases to a thick flake. Leveraging these thickness-dependent electrical conduction transition features, we explore diverse applications of MnTe with varying thicknesses. The semiconductive thin-layer MnTe, serving as the photosensitive channel in a device, achieves superior photoresponse, showcasing considerable potential for photodetection appliations. The semimetallic thick-layer MnTe, acting as the contact electrode in a MoS2 FET, significantly enhances device performance, with carrier mobility increasing from 12.76 cm2∙V−1∙s−1 (Au contact) to 47.34 cm2∙V−1∙s−1 (MnTe contact). This work lays the foundation for the controllable synthesis of nonlayered 2D MnTe and provides insights into its prospective development for constructing innovative electronic and optoelectronic devices.
Two-dimensional (2D) transition-metal dichalcogenides (TMDs) exhibit diverse structures, encompassing a broad spectrum of electronic types ranging from metal, semiconductor, to insulator and topological insulator. They hold immense potential for both Moore and more-than-Moore device applications. Among them, manganese telluride (MnTe), an emerging nonlayered 2D material, has garnered considerable attention due to its exceptional properties and significant application potential in next-generation electronic and optoelectronic devices. However, the controllable synthesis of ultra-thin 2D MnTe remains a great challenge, which hindering the comprehensive exploration of its fundamental properties and potential applications. In this study, we present the synthesis of large-area MnTe nanosheets through chemical vapor deposition growth, showcasing its thickness-dependent properties and device applications. By increasing the growth temperature from 500 to 750 ℃, the MnTe nanosheets’ thickness transitions from thin-layer to a thick flake, the domain size increases from 10 to 125 μm, the morphology changes from triangle to hexagon, culminating in a highly symmetrical round shape. Structural characterization and second harmonic generation measurements reveal that the obtained MnTe nanosheets exhibit high crystallization quality and superior second-order optical nonlinearity. The field effect transistor (FET) constructed with thin-layer MnTe demonstrates a p-type semiconductor characteristic, transitioning to a semimetal feature as the thickness increases to a thick flake. Leveraging these thickness-dependent electrical conduction transition features, we explore diverse applications of MnTe with varying thicknesses. The semiconductive thin-layer MnTe, serving as the photosensitive channel in a device, achieves superior photoresponse, showcasing considerable potential for photodetection appliations. The semimetallic thick-layer MnTe, acting as the contact electrode in a MoS2 FET, significantly enhances device performance, with carrier mobility increasing from 12.76 cm2∙V−1∙s−1 (Au contact) to 47.34 cm2∙V−1∙s−1 (MnTe contact). This work lays the foundation for the controllable synthesis of nonlayered 2D MnTe and provides insights into its prospective development for constructing innovative electronic and optoelectronic devices.
2025, 41(2): 100017
doi: 10.3866/PKU.WHXB202310045
Abstract:
Nuclear magnetic resonance (NMR) spectroscopy serves as a robust non-invasive characterization technique for probing molecular structure and providing quantitative analysis, however, further NMR applications are generally confined by the low sensitivity performance, especially for heteronuclear experiments. Herein, we present a lightweight deep learning protocol for high-quality, reliable, and very fast noise reduction of NMR spectroscopy. Along with the lightweight network advantages and fast computational efficiency, this deep learning (DL) protocol effectively reduces noises and spurious signals, and recovers desired weak peaks almost entirely drown in severe noise, thus implementing considerable signal-to-noise ratio (SNR) improvement. Additionally, it enables the satisfactory spectral denoising in the frequency domain and allows one to distinguish real signals and noise artifacts using solely physics-driven synthetic NMR data learning. Besides, the trained lightweight network model is general for one-dimensional and multi-dimensional NMR spectroscopy, and can be exploited on diverse chemical samples. As a result, the deep learning method presented in this study holds potential applications in the fields of chemistry, biology, materials, life sciences, and among others.
Nuclear magnetic resonance (NMR) spectroscopy serves as a robust non-invasive characterization technique for probing molecular structure and providing quantitative analysis, however, further NMR applications are generally confined by the low sensitivity performance, especially for heteronuclear experiments. Herein, we present a lightweight deep learning protocol for high-quality, reliable, and very fast noise reduction of NMR spectroscopy. Along with the lightweight network advantages and fast computational efficiency, this deep learning (DL) protocol effectively reduces noises and spurious signals, and recovers desired weak peaks almost entirely drown in severe noise, thus implementing considerable signal-to-noise ratio (SNR) improvement. Additionally, it enables the satisfactory spectral denoising in the frequency domain and allows one to distinguish real signals and noise artifacts using solely physics-driven synthetic NMR data learning. Besides, the trained lightweight network model is general for one-dimensional and multi-dimensional NMR spectroscopy, and can be exploited on diverse chemical samples. As a result, the deep learning method presented in this study holds potential applications in the fields of chemistry, biology, materials, life sciences, and among others.
2025, 41(2): 100011
doi: 10.3866/PKU.WHXB202308048
Abstract:
Achieving high energy density batteries is currently a key focus in the field of energy storage. Lithium batteries, due to their high energy density, have garnered significant attention in research. Increasing the upper limit of the battery’s cut-off voltage can boost the energy density of lithium batteries. However, high-voltage conditions can lead to irreversible phase transitions and side reactions in cathode materials, which can degrade battery performance and even result in safety risks, including explosions. The electrolyte can also decompose, causing capacity loss and releasing flammable gases when subjected to high voltage, which can lead to battery swelling and potential combustion and explosions. Designing an ideal cathode electrolyte interphase (CEI) on the cathode’s surface to regulate the electrode-electrolyte interface reaction can effectively enhance the cycling stability of the battery, reduce irreversible phase transitions in the cathode, and improve the oxidation stability of the electrolyte. The ideal CEI should possess high ion conductivity, high thermal stability, and should minimize interface side reactions to ensure optimal battery performance. Understanding the formation and development of CEI is crucial for enhancing battery performance under high voltage. Apart from creating artificial CEI, modifying electrolytes has gained significant attention. By altering the electrolyte recipe, an ideal CEI can be achieved. Electrolyte engineering is considered an effective strategy for attaining an ideal CEI and enhancing the stability of high nickel positive electrodes. This approach is simple, cost-effective, and holds great promise for achieving higher energy density in lithium batteries. To provide a better understanding of CEI in lithium ion batteries (LIBs), this article reviews the latest advancements in CEI, including the formation mechanism of CEI, the key factors influencing CEI, methods for modifying CEI, and techniques for characterizing CEI. Additionally, it summarizes the current status of artificial CEI development and in situ CEI generation through electrolyte design. The aim is to offer fundamental guidance for future research and the design of high-voltage battery CEI. Finally, the article outlines the opportunities and challenges in electrolyte engineering for modified CEI, pointing towards the future direction of constructing an ideal CEI.
Achieving high energy density batteries is currently a key focus in the field of energy storage. Lithium batteries, due to their high energy density, have garnered significant attention in research. Increasing the upper limit of the battery’s cut-off voltage can boost the energy density of lithium batteries. However, high-voltage conditions can lead to irreversible phase transitions and side reactions in cathode materials, which can degrade battery performance and even result in safety risks, including explosions. The electrolyte can also decompose, causing capacity loss and releasing flammable gases when subjected to high voltage, which can lead to battery swelling and potential combustion and explosions. Designing an ideal cathode electrolyte interphase (CEI) on the cathode’s surface to regulate the electrode-electrolyte interface reaction can effectively enhance the cycling stability of the battery, reduce irreversible phase transitions in the cathode, and improve the oxidation stability of the electrolyte. The ideal CEI should possess high ion conductivity, high thermal stability, and should minimize interface side reactions to ensure optimal battery performance. Understanding the formation and development of CEI is crucial for enhancing battery performance under high voltage. Apart from creating artificial CEI, modifying electrolytes has gained significant attention. By altering the electrolyte recipe, an ideal CEI can be achieved. Electrolyte engineering is considered an effective strategy for attaining an ideal CEI and enhancing the stability of high nickel positive electrodes. This approach is simple, cost-effective, and holds great promise for achieving higher energy density in lithium batteries. To provide a better understanding of CEI in lithium ion batteries (LIBs), this article reviews the latest advancements in CEI, including the formation mechanism of CEI, the key factors influencing CEI, methods for modifying CEI, and techniques for characterizing CEI. Additionally, it summarizes the current status of artificial CEI development and in situ CEI generation through electrolyte design. The aim is to offer fundamental guidance for future research and the design of high-voltage battery CEI. Finally, the article outlines the opportunities and challenges in electrolyte engineering for modified CEI, pointing towards the future direction of constructing an ideal CEI.
2025, 41(2): 100013
doi: 10.3866/PKU.WHXB202309036
Abstract:
The surface of energy material is the direct place where energy storage and conversion reactions occur. Thus, the surface chemistry and the structure of the material under real reaction conditions are the key descriptors to clarify the reaction mechanism. However, such surfaces are usually immersed in gaseous or liquid environments under real reaction conditions, so it is not a simple task to identify the real physical and chemical properties of the interface under in situ conditions. X-ray photoelectron spectroscopy (XPS), as a surface-sensitive technique, is one of the main techniques for studying complex composition and electronic structure of material surfaces. However, due to the limited mean free path of photoelectrons in gas, liquid and solid media, the traditional XPS is confined to vacuum conditions, which poses a significant obstacle for studying solid-gas and solid-liquid interfaces under in situ conditions. With the introduction of differentially pumped analyzers and electrostatic lenses system, this limitation no longer restricts XPS only suitable for ultra-high vacuum conditions. With the active development of synchrotron radiation sources worldwide, near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) offers advanced features combined with the benefits of synchrotron radiation sources. Compared to traditional X-ray source, synchrotron radiation sources have significantly higher photon flux and much smaller spot size, which enables more electrons to escape to the electron analyzer, therefore can effectively improve the signal-to-noise ratio and the maximum working pressure, and the continuous wavelength tunability of synchrotron radiation makes experimental measurements more flexible and provides more information on the surface reaction. Over the years, NAP-XPS has rapidly emerged as an influential tool for investigating various solid-gas and solid-liquid interfaces, reflecting the importance of understanding reaction mechanisms and structure-performance relationship of materials under conditions closer to practical reacting conditions, particularly in heterogeneous catalysis. Information at atomic scale can be delivered with surface and interface sensitivity by NAP-XPS in conjunction with several advanced spectroscopy and microscopy techniques. In this paper, we provide a concise overview of recent notable advancements in NAP-XPS to showcase the novel insights generated by research on solid-gas and solid-liquid interfaces in cutting-edge scientific fields. This demonstrates how the knowledge gained from NAP-XPS studies can contribute to a fundamental understanding of reaction mechanisms at a molecular level. Finally, we discuss new challenges and prospects to ensure a comprehensive understanding of this technique and, hopefully, inspire fresh ideas.
The surface of energy material is the direct place where energy storage and conversion reactions occur. Thus, the surface chemistry and the structure of the material under real reaction conditions are the key descriptors to clarify the reaction mechanism. However, such surfaces are usually immersed in gaseous or liquid environments under real reaction conditions, so it is not a simple task to identify the real physical and chemical properties of the interface under in situ conditions. X-ray photoelectron spectroscopy (XPS), as a surface-sensitive technique, is one of the main techniques for studying complex composition and electronic structure of material surfaces. However, due to the limited mean free path of photoelectrons in gas, liquid and solid media, the traditional XPS is confined to vacuum conditions, which poses a significant obstacle for studying solid-gas and solid-liquid interfaces under in situ conditions. With the introduction of differentially pumped analyzers and electrostatic lenses system, this limitation no longer restricts XPS only suitable for ultra-high vacuum conditions. With the active development of synchrotron radiation sources worldwide, near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) offers advanced features combined with the benefits of synchrotron radiation sources. Compared to traditional X-ray source, synchrotron radiation sources have significantly higher photon flux and much smaller spot size, which enables more electrons to escape to the electron analyzer, therefore can effectively improve the signal-to-noise ratio and the maximum working pressure, and the continuous wavelength tunability of synchrotron radiation makes experimental measurements more flexible and provides more information on the surface reaction. Over the years, NAP-XPS has rapidly emerged as an influential tool for investigating various solid-gas and solid-liquid interfaces, reflecting the importance of understanding reaction mechanisms and structure-performance relationship of materials under conditions closer to practical reacting conditions, particularly in heterogeneous catalysis. Information at atomic scale can be delivered with surface and interface sensitivity by NAP-XPS in conjunction with several advanced spectroscopy and microscopy techniques. In this paper, we provide a concise overview of recent notable advancements in NAP-XPS to showcase the novel insights generated by research on solid-gas and solid-liquid interfaces in cutting-edge scientific fields. This demonstrates how the knowledge gained from NAP-XPS studies can contribute to a fundamental understanding of reaction mechanisms at a molecular level. Finally, we discuss new challenges and prospects to ensure a comprehensive understanding of this technique and, hopefully, inspire fresh ideas.
2025, 41(2): 100014
doi: 10.3866/PKU.WHXB202309047
Abstract:
The photoelectrochemical (PEC) technique, as a simple solar energy conversion device, is one of the most promising solutions for addressing both environmental and energy challenges. PEC technique mainly involves the photoconversion process of photoactive materials through carrier excitation and charge transfer under light irradiation, and the active material plays a central role in the entire system. The design and synthesis of highly PEC active materials is crucial for achieving efficient PEC performance. The photoelectric conversion efficiency of photoactive materials mainly depends on two aspects: first, the broad range of light absorption response; second, the rapid separation/transfer rate of photogenerated carriers. Common photosensitive semiconductors can be used as photoelectric active materials, including metal oxides, metal sulfides, organic small molecules and organic polymers. However, achieving a high photoelectric conversion efficiency is challenging due to the inherent limitations of using a single semiconductor material. Exploring functional composites with specific structural compositions can overcome the performance deficiencies of individual semiconductor materials. In addition, the ultraviolet region of the solar spectrum accounts for only about 5%, while visible light accounts for approximately 45%. The development of PEC active materials that can be driven by visible light, such as silver, bismuth, and organic polymer materials, is crucial for the commercial application of PEC technique. Due to the characteristics of bismuth oxyhalide BiOX (X = Cl, Br, I)-based materials, such as an adjustable band gap, a unique layered structure, non-toxicity, a wide light absorption range and outstanding light stability, the PEC technique based on BiOX (X = Cl, Br, I) has become a popular research topic. In this paper, the physicochemical properties of BiOX (X = Cl, Br, I)-based materials are reviewed. The methods used to modify BiOX (X = Cl, Br, I)-based materials from the perspectives of surface and interface are discussed. These modifications aim to improve the utilization rate of sunlight and inhibit the recombination of photogenerated electrons and holes. Additionally, the research progress in microstructure modulation, surface vacancy, functional group modification, metal loading, heteroatom doping and heterojunction construction is emphasized. Through various design strategies, the separation efficiency of photogenerated carriers in BiOX (X = Cl, Br, I) can be effectively enhanced, thereby improving its performance in PEC applications. The significant contributions of modified BiOX (X = Cl, Br, I) to various applications, including PEC sensing, PEC water splitting, photoelectrocatalytic degradation, CO2 reduction, nitrogen fixation and photocatalytic fuel cells are described. Finally, the challenges in the aforementioned applications of BiOX (X = Cl, Br, I) materials are discussed, and the future research and practical application of BiOX (X = Cl, Br, I) are prospected.
The photoelectrochemical (PEC) technique, as a simple solar energy conversion device, is one of the most promising solutions for addressing both environmental and energy challenges. PEC technique mainly involves the photoconversion process of photoactive materials through carrier excitation and charge transfer under light irradiation, and the active material plays a central role in the entire system. The design and synthesis of highly PEC active materials is crucial for achieving efficient PEC performance. The photoelectric conversion efficiency of photoactive materials mainly depends on two aspects: first, the broad range of light absorption response; second, the rapid separation/transfer rate of photogenerated carriers. Common photosensitive semiconductors can be used as photoelectric active materials, including metal oxides, metal sulfides, organic small molecules and organic polymers. However, achieving a high photoelectric conversion efficiency is challenging due to the inherent limitations of using a single semiconductor material. Exploring functional composites with specific structural compositions can overcome the performance deficiencies of individual semiconductor materials. In addition, the ultraviolet region of the solar spectrum accounts for only about 5%, while visible light accounts for approximately 45%. The development of PEC active materials that can be driven by visible light, such as silver, bismuth, and organic polymer materials, is crucial for the commercial application of PEC technique. Due to the characteristics of bismuth oxyhalide BiOX (X = Cl, Br, I)-based materials, such as an adjustable band gap, a unique layered structure, non-toxicity, a wide light absorption range and outstanding light stability, the PEC technique based on BiOX (X = Cl, Br, I) has become a popular research topic. In this paper, the physicochemical properties of BiOX (X = Cl, Br, I)-based materials are reviewed. The methods used to modify BiOX (X = Cl, Br, I)-based materials from the perspectives of surface and interface are discussed. These modifications aim to improve the utilization rate of sunlight and inhibit the recombination of photogenerated electrons and holes. Additionally, the research progress in microstructure modulation, surface vacancy, functional group modification, metal loading, heteroatom doping and heterojunction construction is emphasized. Through various design strategies, the separation efficiency of photogenerated carriers in BiOX (X = Cl, Br, I) can be effectively enhanced, thereby improving its performance in PEC applications. The significant contributions of modified BiOX (X = Cl, Br, I) to various applications, including PEC sensing, PEC water splitting, photoelectrocatalytic degradation, CO2 reduction, nitrogen fixation and photocatalytic fuel cells are described. Finally, the challenges in the aforementioned applications of BiOX (X = Cl, Br, I) materials are discussed, and the future research and practical application of BiOX (X = Cl, Br, I) are prospected.
2025, 41(2): 100018
doi: 10.3866/PKU.WHXB202310046
Abstract:
Photoelectrochemical (PEC) biosensors have attracted intensive attention due to their advantages, including low background, high sensitivity, high specificity and rapid response. In recent years, the introduction of disposable screen-printed electrodes (SPE) has greatly facilitated the development of PEC biosensors, making screen-printed PEC biosensors a promising analytical tool for various applications. Photoactive nanomaterials play a crucial role in the construction of screen-printed PEC biosensors as they can be used not only as photoelectric conversion platforms but also as loading platforms for recognition elements. However, pure photoactive materials usually suffer from some drawbacks, such as inherent toxicity, wide bandgap, and high electron-hole pair recombination rate. Therefore, it is necessary to improve the photoelectric properties of these materials through various design strategies. Moreover, to obtain highly sensitive screen-printed PEC biosensors, it is usually necessary to combine the high-performance photoelectrodes with various signal amplification strategies. In view of this, we provide the first systematic summary of photoactive materials for screen-printed PEC biosensors in this paper, classifying them into four main categories: metal oxides, metal chalcogenides, carbon nanomaterials and bismuth-based nanomaterials. Meanwhile, we focus on the design strategies for photoactive materials, including morphology modulation, elemental doping, and heterostructure construction. In addition, we introduce signal amplification strategies, such as the enzyme label amplification (ELA) strategy, polymerase chain reaction (PCR) strategy, rolling circle amplification (RCA) strategy, and hybridization chain reaction (HCR) strategy, through representative screen-printed PEC immunosensors and screen-printed PEC aptasensors. Finally, we discuss the current challenges and prospects of screen-printed PEC biosensors. We hope to provide readers with a comprehensive understanding of the recent advances in screen-printed PEC biosensors and provide a feasible guidance for the future development of this field.
Photoelectrochemical (PEC) biosensors have attracted intensive attention due to their advantages, including low background, high sensitivity, high specificity and rapid response. In recent years, the introduction of disposable screen-printed electrodes (SPE) has greatly facilitated the development of PEC biosensors, making screen-printed PEC biosensors a promising analytical tool for various applications. Photoactive nanomaterials play a crucial role in the construction of screen-printed PEC biosensors as they can be used not only as photoelectric conversion platforms but also as loading platforms for recognition elements. However, pure photoactive materials usually suffer from some drawbacks, such as inherent toxicity, wide bandgap, and high electron-hole pair recombination rate. Therefore, it is necessary to improve the photoelectric properties of these materials through various design strategies. Moreover, to obtain highly sensitive screen-printed PEC biosensors, it is usually necessary to combine the high-performance photoelectrodes with various signal amplification strategies. In view of this, we provide the first systematic summary of photoactive materials for screen-printed PEC biosensors in this paper, classifying them into four main categories: metal oxides, metal chalcogenides, carbon nanomaterials and bismuth-based nanomaterials. Meanwhile, we focus on the design strategies for photoactive materials, including morphology modulation, elemental doping, and heterostructure construction. In addition, we introduce signal amplification strategies, such as the enzyme label amplification (ELA) strategy, polymerase chain reaction (PCR) strategy, rolling circle amplification (RCA) strategy, and hybridization chain reaction (HCR) strategy, through representative screen-printed PEC immunosensors and screen-printed PEC aptasensors. Finally, we discuss the current challenges and prospects of screen-printed PEC biosensors. We hope to provide readers with a comprehensive understanding of the recent advances in screen-printed PEC biosensors and provide a feasible guidance for the future development of this field.
