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Chinese Journal of Catalysis
2022, Vol. 43, No. 10
Online: 18 October 2022

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Cover: Zhang et al. used femtosecond transient absorption spectroscopy to reveal ultrafast electron transfer kinetics in CdS/Pt heterojunction. Pt nanoparticles constructed an efficient electron transfer channel on the surface of CdS nanorods.

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Heterogeneous N-coordinated single-atom photocatalysts and electrocatalysts Rongchen Shen, Lei Hao, Yun Hau Ng, Peng Zhang, Arramel Arramel, Youji Li, Xin Li 2022, 43 (10):  2453-2483.  DOI: 10.1016/S1872-2067(22)64104-4 Abstract ( 172 )   HTML ( 22 )   PDF (17119KB) ( 312 )   Single-atom catalysts (SACs) have been widely used in heterogeneous catalysis owing to the maximum utilization of metal-active sites with controlled structures and well-defined locations. Upon tailored coordination with nitrogen atom, the metal-nitrogen (M-N)-based SACs have demonstrated interesting physical, optical and electronic properties and have become intense in photocatalysis and electrocatalysis in the past decade. Despite substantial efforts in constructing various M-N-based SACs, the principles for modulating the intrinsic photocatalytic and electrocatalytic performance of their active sites and catalytic mechanism have not been sufficiently studied. Herein, the present review intends to shed some light on recent research made in studying the correlation between intrinsic electronic structure, catalytic mechanism, single-metal atom (SMA) confinement and their photocatalytic and electrocatalytic activities (conversion, selectivity, stability and etc). Based on the analysis of fundamentals of M-N-based SACs, theoretical calculations and experimental investigations, including synthetic methods and characterization techniques, are both included to provide an integral understanding of the underlying mechanisms behind improved coordination structure and observed activity. Finally, the challenges and perspectives for constructing highly active M-N based photocatalysis and electrocatalysis SACs are provided. In particular, extensive technical and mechanism aspects are thoroughly discussed, summarized and analyzed for promoting further advancement of M-N-based SACs in photocatalysis and electrocatalysis.

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MXene quantum dots of Ti3C2: Properties, synthesis, and energy-related applications Chen Guan, Xiaoyang Yue, Jiajie Fan, Quanjun Xiang 2022, 43 (10):  2484-2499.  DOI: 10.1016/S1872-2067(22)64102-0 Abstract ( 511 )   HTML ( 32 )   PDF (14464KB) ( 384 )   The emerging two-dimensional MXene-derived quantum dots (MQDs) have garnered considerable research interest owing to their abundant active edge atoms, excellent electrical conductivity, and remarkable optical properties. Compared with their two-dimensional (2D) counterpart MXene, MQDs with forceful size and quantum confinement effects exhibit more unparalleled properties and have considerably contributed to the advanced photocatalysis, detection, energy storage, and biomedicine fields. This critical review summarizes the fundamental properties of MQDs in terms of structure, electricity, and optics. The mechanism, characteristics, and comparisons of two typical synthesis strategies (traditional chemical method and novel fluorine-free or chemical-free method) are also presented. Furthermore, the similarities and differences between MQDs and 2D MXenes are introduced in terms of their functional groups, light absorption capacity, energy band structure, and other properties. Moreover, recent advances in the applications of MQD-based materials for energy conversion and storage (ECS) are discussed, including photocatalysis, batteries, and supercapacitors. Finally, current challenges and future opportunities for advancing MQD-based materials in the promising ECS field are presented.

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TiO2-based photocatalysts for CO2 reduction and solar fuel generation Tao Zhang, Xiaochi Han, Nhat Truong Nguyen, Lei Yang, Xuemei Zhou 2022, 43 (10):  2500-2529.  DOI: 10.1016/S1872-2067(21)64045-7 Abstract ( 320 )   HTML ( 20 )   PDF (21812KB) ( 331 )   Solar-driven CO2 reduction is an efficient way to convert sustainable solar energy and massive CO2 to renewable solar fuels, such as CH4, HCOOH, HCHO, and CH3OH, etc. Up to now, significant research efforts have been devoted to exploring the reaction path and developing the photocatalysts. In heterogeneous photocatalysis, among the semiconductor-based photocatalysts, titania (TiO2), as an inexpensive and practically sustainable metal oxides, remains the most extensively studied photocatalyst over the past decades. In this review, we summarize the most recent advances in the solar-driven CO2 reduction using TiO2-based photocatalysts, which include the fabrication of heterojunction, surface functional modification, band structure engineering, and morphology design, aiming to improve the CO2 conversion efficiency and selectivity to the desired product. Additionally, photoelectrochemical and photothermal approaches are introduced and the fundamental principles to activate and enhance the performance of TiO2 for the specific reaction are discussed. The exploration of the solar-driven approaches and discussion on the underlying mechanism allow the comprehensive understanding of CO2 photoreduction, that can lead to a rational design and synthesis of TiO2-based photocatalysts.

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Electron transfer kinetics in CdS/Pt heterojunction photocatalyst during water splitting Jianjun Zhang, Gaoyuan Yang, Bowen He, Bei Cheng, Youji Li, Guijie Liang, Linxi Wang 2022, 43 (10):  2530-2538.  DOI: 10.1016/S1872-2067(22)64108-1 Abstract ( 328 )   HTML ( 25 )   PDF (6436KB) ( 262 )   Supporting Information Noble metal cocatalysts have shown great potential in boosting the performance of CdS in photocatalytic water splitting. However, the mechanism and kinetics of electron transfer in noble-metal-decorated CdS during practical hydrogen evolution is not clearly elucidated. Herein, Pt-nanoparticle-decorated CdS nanorods (CdS/Pt) are utilized as the model system to analyze the electron transfer kinetics in CdS/Pt heterojunction. Through femtosecond transient absorption spectroscopy, three dominating exciton quenching pathways are observed and assigned to the trapping of photogenerated electrons at shallow states, recombination of free electrons and trapped holes, and radiative recombination of locally photogenerated electron-hole pairs. The introduction of Pt cocatalyst can release the electrons trapped at the shallow states and construct an ultrafast electron transfer tunnel at the CdS/Pt interface. When CdS/Pt is dispersed in acetonitrile, the lifetime and rate for interfacial electron transfer are respectively calculated to be ~5.5 ps and ~3.5 × 1010 s-1. The CdS/Pt is again dispersed in water to simulate photocatalytic water splitting. The lifetime of the interfacial electron transfer decreases to ~5.1 ps and the electron transfer rate increases to ~4.9 × 1010 s-1, confirming that Pt nanoparticles serve as the main active sites of hydrogen evolution. This work reveals the role of Pt cocatalysts in enhancing the photocatalytic performance of CdS from the perspective of electron transfer kinetics.

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Photocatalytic CO2 conversion of W18O49/CdSe-Diethylenetriamine with high charge transfer efficiency: Synergistic effect of LSPR effect and S-scheme heterojunction Yue Huang, Kai Dai, Jinfeng Zhang, Graham Dawson 2022, 43 (10):  2539-2547.  DOI: 10.1016/S1872-2067(21)64024-X Abstract ( 180 )   HTML ( 11 )   PDF (7017KB) ( 180 )   Non-stoichiometric W18O49 (WO) prepared by solvothermal method has excellent NIR absorption due to the localized surface plasmon resonance effect caused by oxygen vacancies. This has great potential in the field of using sunlight to convert carbon dioxide into organic fuels. In addition, through the amination of CdSe, the one-dimensional/two-dimensional step-scheme (S-scheme) WO/CdSe-diethylenetriamine (WO/CdSe-D) photocatalyst with electron transmission channels driven by visible light to NIR light is constructed by microwave solvothermal method. The LSPR of WO and the synergistic effect of coupling semiconductors to construct S-scheme heterojunctions can improve light utilization and achieve efficient charge carrier transfer efficiency. The optimized photocatalyst of 35%WO/CdSe-D has the best CO2 reduction performance compared to WO and CdSe-D, and the yield is 25.37 µmol h-1 g-1. X-ray photoelectron spectroscopy was used to verify the charge transfer path of the S-scheme WO/CdSe-D heterojunction. This work provides a possibility for the application of non-stoichiometric oxides rich in oxygen vacancies in the field of photocatalytic CO2 reduction.

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g-C3N4/CoTiO3 S-scheme heterojunction for enhanced visible light hydrogen production through photocatalytic pure water splitting Aiyun Meng, Shuang Zhou, Da Wen, Peigang Han, Yaorong Su 2022, 43 (10):  2548-2557.  DOI: 10.1016/S1872-2067(22)64111-1 Abstract ( 141 )   HTML ( 9 )   PDF (2655KB) ( 217 )   Supporting Information Photocatalytic hydrogen (H2) production via water splitting in the absence of sacrificial agents is a promising strategy for producing clean and sustainable hydrogen energy from solar energy. However, the realization of a photocatalytic pure water splitting system with desirable efficiency is still a huge challenge. Herein, visible light photocatalytic H2 production from pure water splitting was successfully achieved using a g-C3N4/CoTiO3 S-scheme heterojunction photocatalyst in the absence of sacrificial agents. An optimum hydrogen evolution rate of 118 μmol∙h-1∙g-1 was reached with the addition of 1.5 wt% CoTiO3. The remarkably promoted hydrogen evolution rate was attributed to the intensified light absorption coupled with the synergistic effect of visible light responsive CoTiO3, the promoted efficiency in charge separation, and the reserved strong redox capacity induced by the S-scheme charge transfer mechanism. This work provides an alternative to visible light-responding oxidation photocatalysts for the construction of S-scheme heterojunctions and high-efficiency photocatalytic systems for pure water splitting.

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Constructing 0D/1D Ag3PO4/TiO2 S-scheme heterojunction for efficient photodegradation and oxygen evolution Yukun Zhu, Yan Zhuang, Lele Wang, Hua Tang, Xianfeng Meng, Xilin She 2022, 43 (10):  2558-2568.  DOI: 10.1016/S1872-2067(22)64099-3 Abstract ( 215 )   HTML ( 6 )   PDF (1673KB) ( 153 )   Supporting Information An S-scheme heterojunction photocatalyst is capable of boosting photogenerated carrier separation and transfer, thus maintaining high photooxidation and photoredox ability. Herein, a 0D Ag3PO4 nanoparticles (NPs)/1D TiO2 nanofibers (NFs) S-scheme heterojunction with intimate interfacial contact was designed via the the hydro-thermal method. Benefiting from the abundant hydroxyl groups and size confinement effect of TiO2 NFs, the average diameter of the Ag3PO4 nanoparticles decreased from 100 to 22 nm, which favored the construction of a 0D/1D geometry heterojunction. The multifunctional Ag3PO4/TiO2 sample exhibited excellent photocatalytic activity and stability in photocatalytic oxygen production (726 µmol/g/h) and photocatalytic degradation of various organic contaminants such as rhodamine B (100%), phenol (60%) and tetracycline hydrochloride (100%). The significant improvements in the photocatalytic performance and stability can be attributed to the intimate interfacial contacts and rich active sites of 0D/1D geometry, fast charge carrier migration, and outstanding photoredox properties induced by the S-scheme charge-transfer route. This work offers a promising strategy for constructing 0D/1D S-scheme heterojunction photocatalysts for improved photocatalytic performance.

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Self-assembly synthesis of S-scheme g-C3N4/Bi8(CrO4)O11 for photocatalytic degradation of norfloxacin and bisphenol A Xiaomeng Gu, Taijie Chen, Jian Lei, Yang Yang, Xiuzhen Zheng, Sujuan Zhang, Qiushi Zhu, Xianliang Fu, Sugang Meng, Shifu Chen 2022, 43 (10):  2569-2580.  DOI: 10.1016/S1872-2067(22)64142-1 Abstract ( 109 )   HTML ( 6 )   PDF (2567KB) ( 104 )   Supporting Information To realize the high-efficiency photodegradation of antibiotics, a novel S-scheme heterojunction photocatalyst g-C3N4/Bi8(CrO4)O11 was proposed and successfully prepared in this work. The 10% g-C3N4/Bi8(CrO4)O11 heterojunction exhibits the highest degradation rate of norfloxacin (NOR) and bisphenol A (BPA). The degradation rate of NOR on 10% g-C3N4/Bi8(CrO4)O11 is about 1.38 and 2.33 times higher than that of pure Bi8(CrO4)O11 and g-C3N4, respectively. Further, the degradation rate of BPA over 10% g-C3N4/Bi8(CrO4)O11 heterojunction is bout 1.35 and 9.11 times higher than that of pure Bi8(CrO4)O11 and g-C3N4, respectively. The formation of S-scheme heterojunction facilitates the separation of photogenerated electron-hole pairs and reduces the recombination of charge carriers, which was confirmed by photocurrent, electrochemical impedance spectroscopy, steady-state and time-resolved transient photoluminescence spectrum, etc. The in-situ X-ray photoelectron spectroscopy, radical trapping experiments and electron paramagnetic resonance results demonstrate that the charge transfer is in accord with S-scheme mechanism.

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All-organic covalent organic frameworks/perylene diimide urea polymer S-scheme photocatalyst for boosted H2 generation Zizhan Liang, Rongchen Shen, Peng Zhang, Youji Li, Neng Li, Xin Li 2022, 43 (10):  2581-2591.  DOI: 10.1016/S1872-2067(22)64130-5 Abstract ( 304 )   HTML ( 11 )   PDF (7463KB) ( 226 )   Conjugated covalent organic frameworks (COFs) hold great promise in photocatalytic hydrogen evolution owing to their high crystallinity, large surface area, and distinct structure. However, COFs exhibit poor charge separation. Therefore, investigating highly effective COF-based photocatalysts is crucial. For the first time, conjugated COF/perylene diimide urea polymer (PUP) all-organic heterostructure with S-scheme interfacial charge-transfer channels was successfully developed and manufactured via in situ coupling of the two-dimensional triazine-based imine-linked COF (denoted as TATF-COF) with PUP. The optimal photocatalytic hydrogen-evolution rate of 94.5 mmol h-1 g-1 for TATF-COF/PUP is 3.5 times that of pure TATF-COF and is comparable to or even higher than that of the previously reported COF-based photocatalysts, resulting in an apparent quantum efficiency of up to 19.7% at 420 nm. The improved directional S-scheme charge transfer driven by the tuned built-in electric field and enhanced oxidation and reduction reaction rates of the photogenerated carriers contribute synergistically to the boosted photocatalytic H2 evolution. Experiments and theoretical studies reveal plausible H2 evolution and spatial S-scheme charge-separation mechanisms under visible-light irradiation. This study provides advanced methods for constructing all-organic S-scheme high-efficiency photocatalysts by the modulation of band structures.

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2D/2D S-scheme heterojunction with a covalent organic framework and g-C3N4 nanosheets for highly efficient photocatalytic H2 evolution Pengyu Dong, Aicaijun Zhang, Ting Cheng, Jinkang Pan, Jun Song, Lei Zhang, Rongfeng Guan, Xinguo Xi, Jinlong Zhang 2022, 43 (10):  2592-2605.  DOI: 10.1016/S1872-2067(22)64094-4 Abstract ( 185 )   HTML ( 7 )   PDF (7481KB) ( 218 )   Supporting Information The fabrication of S-scheme heterojunctions with fast charge transfer and good interface contacts, such as intermolecular π-π interactions, is a promising approach to improve photocatalytic performance. A unique two-dimensional/two-dimensional (2D/2D) S-scheme heterojunction containing TpPa-1-COF/g-C3N4 nanosheets (denoted as TPCNNS) was developed. The established maximum interfacial interaction between TpPa-1-COF NS and g-C3N4 NS may result in a π-π conjugated heterointerface. Furthermore, the difference in the work functions of TpPa-1-COF and g-C3N4 results in a large Fermi level gap, leading to upward/downward band edge bending. The spontaneous interfacial charge transfer from g-C3N4 to TpPa-1-COF at the π-π conjugated interface area results in the presence of a built-in electric field, according to the charge density difference analysis based on density functional theory calculations. Such an enhanced built-in electric field can efficiently drive directional charge migration via the S-scheme mechanism, which enhances charge separation and utilization. Thus, an approximately 2.8 and 5.6 times increase in the photocatalytic hydrogen evolution rate was recorded in TPCNNS-2 (1153 μmol g-1 h-1) compared to pristine TpPa-1-COF and g-C3N4 NS, respectively, under visible light irradiation. Overall, this work opens new avenues in the fabrication of 2D/2D π-π conjugated S-scheme heterojunction photocatalysts with highly efficient hydrogen evolution performance.

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Ultrasonic-assisted fabrication of Cs2AgBiBr6/Bi2WO6 S-scheme heterojunction for photocatalytic CO2 reduction under visible light Jiaqi Wang, Hao Cheng, Dingqiong Wei, Zhaohui Li 2022, 43 (10):  2606-2614.  DOI: 10.1016/S1872-2067(22)64091-9 Abstract ( 152 )   HTML ( 5 )   PDF (2067KB) ( 161 )   Supporting Information In this manuscript, Cs2AgBiBr6/Bi2WO6 nanocomposites was fabricated via an ultrasonic-assisted process. The activity of the as-obtained Cs2AgBiBr6/Bi2WO6 nanocomposites for photocatalytic CO2 reduction was studied under visible light. The as-obtained Cs2AgBiBr6/Bi2WO6 nanocomposites show a superior activity for photocatalytic CO2 reduction to produce CH4 and CO, with an optimum activity achieved over 0.5 Cs2AgBiBr6/Bi2WO6. The obvious superior activity observed over Cs2AgBiBr6/Bi2WO6 nanocomposites as compared with bare Cs2AgBiBr6 and bare Bi2WO6 as well as a mechanical mixture of Cs2AgBiBr6 and Bi2WO6 can be owe to the fabrication of an efficient S-scheme heterojunction, which accelerates the separation of the photogenerated charge carriers in Cs2AgBiBr6 and Bi2WO6 without sacrificing the high redox capability of Cs2AgBiBr6 and Bi2WO6. This work demonstrates that the coupling of two photocatalytic materials with staggered band alignment to form an S-scheme heterojunction is an effective strategy to develop efficient photocatalytic systems and also highlights the promising role of using lead free perovskites in photocatalysis.

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A novel S-scheme 3D ZnIn2S4/WO3 heterostructure for improved hydrogen production under visible light irradiation Mengyu Zhao, Sen Liu, Daimei Chen, Sushu Zhang, Sónia A. C. Carabineiro, Kangle Lv 2022, 43 (10):  2615-2624.  DOI: 10.1016/S1872-2067(22)64134-2 Abstract ( 198 )   HTML ( 8 )   PDF (4754KB) ( 220 )   Supporting Information In-plane epitaxial growth of ZnIn2S4 nanosheets on the surface of hexagonal phase WO3 nanorods was achieved by a facile solvothermal method. The unique 3D heterostructure not only enlarged the specific surface area, but also red-shifted the absorption edge from 381 to 476 nm to improve the light harvesting ability, which largely enhanced the photocatalytic hydrogen evolution. The H2 production rate of the best performing ZnIn2S4/WO3 photocatalyst (ZIS-2.5/W, the material with a molar rate of ZnIn2S4 (ZIS) to WO3 (W) of 2.5) was 300 μmol·g-1·h-1, around 417 times and 2 times higher than the rates of pristine WO3 and ZnIn2S4, respectively. The apparent quantum efficiency for ZIS-2.5/W composite was up to 2.81% at 400 nm. Based on the difference in Fermi levels between WO3 and ZnIn2S4, and the distribution of the redox active sites on WO3/ZnIn2S4 heterostructure, a S-scheme electron transfer mechanism was proposed to illustrate the improved photocatalytic activity of WO3/ZnIn2S4 heterojunction, which not only stimulated the spatial separation of the photogenerated charge carriers, but also maintained the strong reduction/oxidation ability of the photocatalyst.

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3D Fe-MOF embedded into 2D thin layer carbon nitride to construct 3D/2D S-scheme heterojunction for enhanced photoreduction of CO2 Xiaoxue Zhao, Mengyang Xu, Xianghai Song, Weiqiang Zhou, Xin Liu, Pengwei Huo 2022, 43 (10):  2625-2636.  DOI: 10.1016/S1872-2067(22)64115-9 Abstract ( 198 )   HTML ( 7 )   PDF (6034KB) ( 99 )   Supporting Information Regulating charge transfer to achieve specific transfer path can improve electron utilization and complete efficient photoreduction of CO2. Here, we fabricated a S-scheme heterojunction of CN/Fe-MOF by an in-situ assembly strategy. The S-scheme charge transfer mechanism was confirmed by band structure, electron spin resonance (ESR) and work function (Φ) analysis. On the one hand, the response of Fe-MOF in the visible region improved the utilization of light energy, thus increasing the ability of CN/Fe-MOF to generate charge carriers. On the other hand, CN, as the active site, not only had strong adsorption capacity for CO2, but also retained photogenerated electrons with high reduction capacity because of S-scheme charge transfer mechanism. Hence, in the absence of any sacrificial agent and cocatalyst, the optimized 50CN/Fe-MOF obtained the highest CO yield (19.17 μmol g-1) under UV-Vis irradiation, which was almost 10 times higher than that of CN. In situ Fourier transform infrared spectra not only revealed that the photoreduction of CO2 occurred at the CN, but also demonstrated that the S-scheme charge transfer mechanism enabled 50CN/Fe-MOF to have a stronger ability to generate HCOO- than CN.

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Construction of 3D flowers-like O-doped g-C3N4-[N-doped Nb2O5/C] heterostructure with direct S-scheme charge transport and highly improved visible-light-driven photocatalytic efficiency Fahim A. Qaraah, Samah A. Mahyoub, Abdo Hezam, Amjad Qaraah, Qasem A. Drmosh, Guangli Xiu 2022, 43 (10):  2637-2651.  DOI: 10.1016/S1872-2067(21)64038-X Abstract ( 236 )   HTML ( 7 )   PDF (6375KB) ( 173 )   Supporting Information Constructing a suitable heterojunction photocatalytic system from two photocatalytic materials is an efficient approach for designing extremely efficient photocatalysts for a broader range of environmental, medical, and energy applications. Recently, the construction of a step-scheme heterostructure system (hereafter called the S-scheme) has received widespread attention in the photocatalytic field due to its ability to achieve efficient photogenerated carrier separation and obtain strong photo-redox ability. Herein, a novel S-scheme heterojunction system consisting of 2D O-doped g-C3N4 (OCN) nanosheets and 3D N-doped Nb2O5/C (N-NBO/C) nanoflowers is constructed via ultrasonication and vigorous agitation technique followed by heat treatment for the photocatalytic degradation of Rhodamine B (RhB). Detailed characterization and decomposition behaviour of RhB showed that the fabricated material shows excellent photocatalytic efficiency and stability towards RhB photodegradation under visible-light illumination. The enhanced performance could be attributed to the following factors: fast charge transfer, highly-efficient charge separation, extended lifetime of photoinduced charge carriers, and the high redox capability of the photoinduced charges in the S-scheme system. Various trapping experiment conditions and electron paramagnetic resonance provide clear evidence of the S-scheme photogenerated charge transfer path, meanwhile, the RhB mineralization degradation pathway was also investigated using LC-MS. This study presents an approach to constructing Nb2O5-based S-scheme heterojunctions for photocatalytic applications.

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S-Scheme photocatalyst TaON/Bi2WO6 nanofibers with oxygen vacancies for efficient abatement of antibiotics and Cr(VI): Intermediate eco-toxicity analysis and mechanistic insights Shijie Li, Mingjie Cai, Yanping Liu, Chunchun Wang, Kangle Lv, Xiaobo Chen 2022, 43 (10):  2652-2664.  DOI: 10.1016/S1872-2067(22)64106-8 Abstract ( 284 )   HTML ( 6 )   PDF (4220KB) ( 322 )   Supporting Information Enlightened by natural photosynthesis, developing efficient S-scheme heterojunction photocatalysts for deleterious pollutant removal is of prime importance to restore environment. Herein, novel TaON/Bi2WO6 S-scheme heterojunction nanofibers were designed and developed by in-situ growing Bi2WO6 nanosheets with oxygen vacancies (OVs) on TaON nanofibers. Thanks to the efficiently spatial charge disassociation and preserved great redox power by the unique S-scheme mechanism and OVs, as well as firmly interfacial contact by the core-shell 1D/2D fibrous hetero-structure via the in-situ growth, the optimized TaON/Bi2WO6 heterojunction unveils exceptional visible-light photocatalytic property for abatement of tetracycline (TC), levofloxacin (LEV), and Cr(VI), respectively by 2.8-fold, 1.0-fold, and 1.9-fold enhancement compared to the bare Bi2WO6, while maintaining satisfactory stability. Furthermore, the systematic photoreaction tests indicate TaON/Bi2WO6 has the high practicality in the elimination of pollutants in aquatic environment. The degradation pathway of tetracycline and intermediate eco-toxicity were determined based on HPLC-MS combined with QSAR calculation, and a possible photocatalytic mechanism was elucidated. This work provides a guideline for designing high-performance TaON-based S-scheme photocatalysts with defects for environment protection.

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Noble-metal-free plasmonic MoO3‒x-based S-scheme heterojunction for photocatalytic dehydrogenation of benzyl alcohol to storable H2 fuel and benzaldehyde Yingcong Wei, Qiqi Zhang, Ying Zhou, Xiongfeng Ma, Lele Wang, Yanjie Wang, Rongjian Sa, Jinlin Long, Xianzhi Fu, Rusheng Yuan 2022, 43 (10):  2665-2677.  DOI: 10.1016/S1872-2067(22)64124-X Abstract ( 125 )   HTML ( 3 )   PDF (12422KB) ( 131 )   Supporting Information Simultaneous generation of H2 fuel and value-added chemicals has attracted increasing attention since the photogenerated electrons and holes can be both employed to convert solar light into chemical energy. Herein, for realizing UV-visible-NIR light driven dehydrogenation of benzyl alcohol (BA) into benzaldehydes (BAD) and H2, a novel localized surface plasmon resonance (LSPR) enhanced S-scheme heterojunction was designed by combining noble-metal-free plasmon MoO3-x as oxidation semiconductor and Zn0.1Cd0.9S as reduction semiconductor. The photoredox system of Zn0.1Cd0.9S/MoO3-x displayed an unconventional reaction model, in which the BA served as both electron donor and acceptor. The S-scheme charge transfer mechanism induced by the formed internal electric field enhanced the redox ability of charge carriers thermodynamically and boosted charge separation kinetically. Moreover, due to the LSPR effect of MoO3‒x nanosheets, Zn0.1Cd0.9S/MoO3‒x photocatalysts exhibited strong absorption in the region of full solar spectrum. Therefore, the Zn0.1Cd0.9S/MoO3‒x composite generated H2 and BAD simultaneously via selective oxidation of BA with high production (34.38 and 33.83 mmol•g-1 for H2 and BAD, respectively) upon full solar illumination. Even under NIR light irradiation, the H2 production rate could up to 94.5 mmol•g-1•h-1. In addition, the Zn0.1Cd0.9S/MoO3-x composite displayed effective photocatalytic H2 evolution rate up to 149.2 mmol•g-1•h-1 from water, which was approximate 6 times that of pure Zn0.1Cd0.9S. This work provides a reference for rational design of plasmonic S-scheme heterojunction photocatalysts for coproduction of high-value chemicals and solar fuel production.

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Singlet oxygen synergistic surface-adsorbed hydroxyl radicals for phenol degradation in CoP catalytic photo-Fenton Haoran Yu, Danxu Liu, Hengyi Wang, Haishuang Yu, Qingyun Yan, Jiahui Ji, Jinlong Zhang, Mingyang Xing 2022, 43 (10):  2678-2689.  DOI: 10.1016/S1872-2067(22)64117-2 Abstract ( 296 )   HTML ( 12 )   PDF (4317KB) ( 182 )   Supporting Information In recent years, there have been numerous studies on Fenton or Fenton-like reactions mediated by nonfree radicals such as singlet oxygen (1O2); however, there are few studies on the synergistic effect of 1O2 and free radicals on the degradation of organic molecules, such as phenol in Fenton reaction. In this study, a cocatalyst, CoP, commonly used in photocatalysis was synthesized using a simple two-step method, and a CoP/Fe2+/AM1.5 system was constructed by introducing Fe2+ and simulated sunlight (AM1.5) irradiation. The newly constructed CoP/Fe2+/AM1.5 system could effectively degrade various organic pollutants, including dyes, phenols, and antibiotics. Radical quenching experiments and electron paramagnetic resonance detection confirmed that there were three reactive oxygen species (ROS) in the CoP/Fe2+/AM1.5 system, including •OHads, •O2-, and 1O2. Further, combined with the liquid chromatogram of phenol, its intermediate products, and the fluorescence diagram of o-hydroxybenzoic acid, it can be concluded that a synergistic effect exists between 1O2 and the surface-adsorbed •OHads in the CoP/Fe2+/AM1.5 system. The controllable formation of surface 1O2 and •OHads was achieved through the oxidation (Co3+) and reduction (Pδ-) centers exposed on the CoP surface, and the synergistic effect between them results in phenol’s hydroxylation, ring-opening, and degradation. The study of this new mechanism provides a new perspective for revealing the surface interface reaction between ROS and organic pollutants.

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An efficient strategy for photocatalytic hydrogen peroxide production over oxygen-enriched graphitic carbon nitride with sodium phosphate Yu Zhang, Ling Zhang, Di Zeng, Wenjing Wang, Juxue Wang, Weimin Wang, Wenzhong Wang 2022, 43 (10):  2690-2698.  DOI: 10.1016/S1872-2067(22)64114-7 Abstract ( 198 )   HTML ( 6 )   PDF (4837KB) ( 242 )   Supporting Information Photocatalytic hydrogen peroxide (H2O2) production is a promising strategy to replace the traditional production processes; however, the inefficient H2O2 productivity limits its application. In this study, oxygen-rich g-C3N4 with abundant nitrogen vacancies (OCN) was synthesized for photocatalytic H2O2 production. X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy indicated that oxygen-containing functional groups (-COOH and C-O-C) were obtained. Electron paramagnetic resonance confirmed the successful introduction of nitrogen vacancies. OCN exhibited efficient photocatalytic H2O2 production performance of 1965 µmol L-1 h-1 in air under visible-light irradiation. The high H2O2 production was attributed to the enhanced adsorption of oxygen, enlarged specific surface area, and promoted carrier separation. An increased H2O2 production rate (5781 µmol L-1 h-1) was achieved in a Na3PO4 solution. The improved performance was attributed to the changed reactive oxygen species. Specifically, the adsorbed PO43- on the surface of the OCN promoted the transfer of holes to the catalyst surface. •O2- obtained by O2 reduction reacted with adjacent holes to generate 1O2, which could efficiently generate H2O2 with isopropanol. Additionally, PO43-, as a stabilizer, inhibited the decomposition of H2O2.

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A thioether-functionalized pyrene-based covalent organic framework anchoring ultrafine Au nanoparticles for efficient photocatalytic hydrogen generation Zhiming Zhou, Chuanbiao Bie, Peize Li, Bien Tan, Yan Shen 2022, 43 (10):  2699-2707.  DOI: 10.1016/S1872-2067(22)64118-4 Abstract ( 176 )   HTML ( 6 )   PDF (1777KB) ( 201 )   Supporting Information Covalent organic frameworks (COFs) have lately emerged as a blooming class of potential materials for photocatalytic water splitting because of their high crystallinity, huge surface areas, and structural versatility. However, the photocatalytic performance for most pure COFs face some limitations factors, such as the significant recombination of photogenerated carriers and slow charge transfer. Herein, a novel thioether-functionalized pyrene-based COF (S4-COF) was effectively produced and chosen as a support for the immobilization of ultrafine gold nanoparticles (Au NPs). S4-COF photocatalyst with Au as cocatalyst demonstrates remarkable photocatalytic activity with a H2 generation rate of 1377 μmol g-1 h-1 under visible light (>420 nm), which is ca. 4.5-fold increase comparing to that of pure S4-COF (302 μmol g-1 h-1). Au NPs anchored on S4-COF possess an ultrafine size distribution ranging from 1.75 to 6.25 nm with an average size centered at 3.8 nm, which benefits from the coordination interaction between thioether groups and Au. Meanwhile, the produced Au@S4-COF can generate a stable photocatalytic H2 generation during the four recycles and preserve its crystallinity structure after the stability testing. The Au NPs anchored on the S4-COF photocatalyst can greatly accelerate the separation of photogenerated carriers and increase charge transfer because of the combined function of Au NPs and thioether groups. Such a method can not only prevent the aggregation of Au NPs onto thioether-containing COFs to achieve long-term photostability but also allow uniform dispersion for an ordered structure of photocatalysts. This work provides a rational strategy for designing and preparing COF-based photocatalysts for solar-driven H2 production.

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Mechanochemical preparation and application of graphdiyne coupled with CdSe nanoparticles for efficient photocatalytic hydrogen production Zhaobo Fan, Xin Guo, Mengxue Yang, Zhiliang Jin 2022, 43 (10):  2708-2719.  DOI: 10.1016/S1872-2067(21)64053-6 Abstract ( 120 )   HTML ( 9 )   PDF (8541KB) ( 242 )   Graphdiyne (GDY) has attracted considerable attention as a new two-dimensional (2D) carbon hybrid material because of its good conductivity, adjustable electronic structure, and special electron transfer enhancement properties. GDY has great potential in the field of photocatalytic water splitting for hydrogen evolution, owing to its unique properties. In this study, GDY was successfully prepared by the mechanochemical coupling of precursors C6Br6 and CaC2 using a ball-milling approach. The prepared GDY, especially its microstructure and composition, was well characterized using different techniques such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared, and Raman characterization techniques. By exploiting the unique two-dimensional (2D) structure and outstanding light absorption properties of GDY, GDY/CdSe 2D/0D heterojunctions were successfully established and applied to photocatalytic hydrogen evolution. The hydrogen evolution activity of GDY/CdSe-20, a type of composite material, reached 6470 μmol g-1 h-1, which is 461 and 40 times higher than that of GDY and CdSe, respectively. Moreover, the fine electrical conductivity of GDY enabled rapid and effective transfer of the photogenerated electrons in CdSe into the hydrogen evolution reaction. The transfer path of the photogenerated electrons was studied through XPS with in situ irradiation, and a reasonable mechanism for the hydrogen evolution reaction was proposed. This study provides a feasible approach for the large-scale preparation of GDY and demonstrates the prospects of GDY in the field of photocatalysis.

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Dual transfer channels of photo-carriers in 2D/2D/2D sandwich-like ZnIn2S4/g-C3N4/Ti3C2 MXene S-scheme/Schottky heterojunction for boosting photocatalytic H2 evolution Lele Wang, Tao Yang, Lijie Peng, Qiqi Zhang, Xilin She, Hua Tang, Qinqin Liu 2022, 43 (10):  2720-2731.  DOI: 10.1016/S1872-2067(22)64133-0 Abstract ( 98 )   HTML ( 7 )   PDF (6617KB) ( 160 )   Supporting Information Construction of multi-channels of photo-carrier migration in photocatalysts is favor to boost conversion efficiency of solar energy by promoting the charge separation and transfer. Herein, a ternary ZnIn2S4/g-C3N4/Ti3C2 MXene hybrid composed of S-scheme junction integrated Schottky-junction was fabricated using a simple hydrothermal approach. All the components (g-C3N4, ZnIn2S4 and Ti3C2 MXene) demonstrated two-dimensional (2D) nanosheets structure, leading to the formation of a 2D/2D/2D sandwich-like structure with intimate large interface for carrier migration. Furthermore, the photogenerated carriers on the g-C3N4 possessed dual transfer channels, including one route in S-scheme transfer mode between the g-C3N4 and ZnIn2S4 and the other route in Schottky-junction between g-C3N4 and Ti3C2 MXene. Consequently, a highly efficient carrier separation and transport was realized in the ZnIn2S4/g-C3N4/Ti3C2 MXene heterojunction. This ternary sample exhibited wide light response from 200 to 1400 nm and excellent photocatalytic H2 evolution of 2452.1 μmol∙g-1∙h-1, which was 200, 3, 1.5 and 1.6 times of g-C3N4, ZnIn2S4, ZnIn2S4/Ti3C2 MXene and g-C3N4/ZnIn2S4 binary composites. This work offers a paradigm for the rational construction of multi-electron pathways to regulate the charge separation and migration via the introduction of dual-junctions in catalytic system.

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Enantioselective intermolecular [2 + 2] photocycloadditions of vinylazaarenes with triplet-state electron-deficient olefins Dong Tian, Xin Sun, Shanshan Cao, Er-Meng Wang, Yanli Yin, Xiaowei Zhao, Zhiyong Jiang 2022, 43 (10):  2732-2742.  DOI: 10.1016/S1872-2067(22)64156-1 Abstract ( 293 )   HTML ( 10 )   PDF (1760KB) ( 196 )   The development of catalytic asymmetric radical reactions is an attractive but formidable task. The high reactivity of radicals enables the use of readily accessible feedstocks and mild reaction conditions, but it leads to substantial difficulty for chiral catalysts to provide sufficient enantiocontrol. Moreover, a racemic background process is often inevitable, further deteriorating enantioselectivity. In this regard, an effective protocol has been established for enantioselective intermolecular [2 + 2] photocycloadditions to overcome the challenges, which is capitalising on the ground-state preassociations of chiral catalysts with photoactivated substrates. Here, we report the viability of substrate-differentiating synergistic catalysis for this important reaction. In this new platform, energy transfer occurs between DPZ as a photosensitizer and enones or (E)-2-substituted vinylazaarenes for producing triplet-state species, and chiral phosphoric acid interacts with ground-state 2-vinylazaarenes via hydrogen bonding for subsequent enantiofacial cycloaddition. Although all active species are dispersed in the reaction system, valuable enantioenriched mono- and di-azaarene-functionalized cyclobutanes are obtained efficiently and selectively. In addition to constructing all-carbon quaternary stereocentres, flexible modulation of azaaryl groups and other substituents on the cyclobutane ring is also operative.