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Chinese Journal of Catalysis
2022, Vol. 43, No. 9
Online: 18 September 2022

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Cover: Nonsacrificial H₂ evolution by a graphitic carbon nitride (g-C₃N₄) photocatalyst from aqueous solutions containing reversible electron donors is achieved. A Pt-core/CrO_x-shell cocatalyst suppresses a backward reaction of reversible electron donors and enables the construction of a Z-scheme overall water-splitting system under visible light by combination with a surface modified tungsten trioxide photocatalyst.

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Special column on renewable fuel synthesis by photocatalysis and photoelectrocatalysis

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Preface to special column on renewable fuel synthesis by photocatalysis and photoelectrocatalysis Junwang Tang, Lianzhou Wang, Robert Godin, Roland Marschall 2022, 43 (9):  2271-2272.  DOI: 10.1016/S1872-2067(22)64147-0 Abstract ( 202 )   HTML ( 28 )   PDF (684KB) ( 185 )

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Recent advances and perspectives in cobalt-based heterogeneous catalysts for photocatalytic water splitting, CO2 reduction, and N2 fixation Wanjun Sun, Jiayu Zhu, Meiyu Zhang, Xiangyu Meng, Mengxue Chen, Yu Feng, Xinlong Chen, Yong Ding 2022, 43 (9):  2273-2300.  DOI: 10.1016/S1872-2067(21)63939-6 Abstract ( 529 )   HTML ( 35 )   PDF (9595KB) ( 529 )   Solar-driven conversion of carbon dioxide, water and nitrogen into high value-added fuels (e.g. H2, CO, CH4, CH3OH, NH3 and so on) is regarded as an environmental-friendly and ideal route for relieving the greenhouse gas effect and countering energy crisis, which is an attractive and challenging topic. Hence, various types of photocatalysts have been developed successively to meet the requirements of these photocatalysis. Among them, cobalt-based heterogeneous catalysts emerge as one of the most promising photocatalysts that open up alluring vistas in the field of solar-to-fuels conversion, which can effectively enhance photocatalytic efficiency by extending light absorption range, promoting charge separation, providing active sites, and lowering reaction barrier. In this review, we first present the working principles of cobalt-based heterogeneous catalysts for photocatalytic water splitting, CO2 reduction, and N2 fixation. Second, five efficient strategies including surface modification, morphology modulation, crystallinity controlling, crystal engineering and doping, are discussed for improving the photocatalytic performance with different types cobalt-based catalysts (cobalt nanoparticles and single atom, oxides, sulfides, phosphides, MOFs, COFs, LDHs, carbide, and nitrides). Third, we outline the applications for the state-of-the-art photocatalytic CO2 reduction and water splitting, and nitrogen fixation over cobalt-based heterogeneous catalysts. Finally, the central challenges and possible improvements of cobalt-based photocatalysis in the future are presented. The purpose of this review is to summarize the past experience and lessons, and provide reference for the further development of cobalt-based photocatalysis technology.

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Single-atom catalysts on metal-based supports for solar photoreduction catalysis Huayang Zhang, Wenjie Tian, Xiaoguang Duan, Hongqi Sun, Yingping Huang, Yanfen Fang, Shaobin Wang 2022, 43 (9):  2301-2315.  DOI: 10.1016/S1872-2067(21)63918-9 Abstract ( 340 )   HTML ( 26 )   PDF (4829KB) ( 376 )   Metal atoms atomically dispersed on an inorganic metal-based support compose a unique category of single atom catalysts (SACs) and have important applications in catalytic photoreduction reactions, including H2 evolution reaction, CO2 reduction reaction, and N2 reduction reaction. In this minreview, we summarized the typical metal-support interaction (M-SI) patterns for successful anchoring of single-atom metals on metallic compound supports. Subsequently, the contribution of the dispersed single metal atoms and M-SI to photocatalytic reactions with improved activity, selectivity, and stability are highlighted, such as by accelerating charge transfer, regulating band structure of the support, acting as the reductive sites, and/or increasing catalytic selectivity. Finally, some challenges and perspectives of future development are proposed. We anticipate that this minireview will be a beneficial supplement for a comprehensive perception of metal-based material supported SACs and their application in heterogeneous photo-reductive catalysis.

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Visible-light-driven nonsacrificial hydrogen evolution by modified carbon nitride photocatalysts Shunta Nishioka, Kengo Shibata, Yugo Miseki, Kazuhiro Sayama, Kazuhiko Maeda 2022, 43 (9):  2316-2320.  DOI: 10.1016/S1872-2067(21)64015-9 Abstract ( 238 )   HTML ( 16 )   PDF (1758KB) ( 174 )   Supporting Information Pt-loaded graphitic carbon nitride (g-C3N4) is known to be a good photocatalyst for H2 evolution under visible light. In most cases, however, sacrificial electron donors such as triethanolamine are required for the water-splitting operation, and nonsacrificial H2 evolution by g-C3N4 remains a challenge. In this work, we investigated the photocatalytic activities of carbon nitride nanosheet (NS-C3N4), which was prepared by thermal treatment of urea, for nonsacrificial H2 evolution using reversible electron donors under visible light (λ > 400 nm). Whereas Pt-loaded NS-C3N4 did not produce H2 from aqueous solutions containing I-, Fe2+, or [Fe(CN)6]4-, modification of the Pt/NS-C3N4 photocatalyst with CrOx led to observable H2 evolution. Transmission electron microscopy observations and energy-dispersive X-ray spectroscopic analysis suggested that a Pt-core/CrOx-shell structure was formed on the NS-C3N4. The CrOx/Pt/NS-C3N4 served as a H2-evolution photocatalyst for visible-light-driven Z-scheme overall water splitting, in combination with a modified WO3 photocatalyst, in the presence of a [Fe(CN)6]3-/4- redox mediator.

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Conformal BiVO4/WO3 nanobowl array photoanode for efficient photoelectrochemical water splitting Wen Zhang, Meng Tian, Haimiao Jiao, Hai-Ying Jiang, Junwang Tang 2022, 43 (9):  2321-2331.  DOI: 10.1016/S1872-2067(21)63927-X Abstract ( 335 )   HTML ( 17 )   PDF (2831KB) ( 219 )   Supporting Information As one of the most promising photoanode candidates for photoelectrochemical (PEC) water splitting, the photocurrent density of BiVO4 still needs to be further improved in order to meet the practical application. In this work, a highly-matched BiVO4/WO3 nanobowl (NB) photoanode was constructed to enhance charge separation at the interface of the junction. Upon further modification of the BiVO4/WO3NB surface by NiOOH/FeOOH as an oxygen evolution cocatalyst (OEC) layer, a high photocurrent density of 3.05 mA cm-2 at 1.23 V vs. RHE has been achieved, which is about 5-fold higher than pristine BiVO4 in neutral medium under AM 1.5 G illumination. 5 times higher IPCE at 450 nm is also achieved compared with the BiVO4 photoanode, leading to about 95% faradaic efficiency for both H2 and O2 gas production. Systematic studies attribute the significantly enhanced PEC performance to the smaller BiVO4 particle size (< 90 nm) than its hole diffusion length (~100 nm), the improved charge separation of BiVO4 by the single layer WO3 nanobowl array and the function of OEC layers. Such WO3NB possesses much smaller interface resistance with the substrate FTO glass and larger contact area with BiVO4 nanoparticles. This approach provides new insights to design and fabricate BiVO4-based heterojunction photoanode for higher PEC water splitting performance.

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Precisely decorating CdS on Zr-MOFs through pore functionalization strategy: A highly efficient photocatalyst for H2 production Haijun Hu, Kailai Zhang, Ge Yan, Litong Shi, Baohua Jia, Hongwei Huang, Yu Zhang, Xiaodong Sun, Tianyi Ma 2022, 43 (9):  2332-2341.  DOI: 10.1016/S1872-2067(21)63949-9 Abstract ( 258 )   HTML ( 25 )   PDF (5764KB) ( 275 )   Supporting Information Different materials, such as metal sulphides, are often combined with metal-organic frameworks (MOFs) to develop multi-functional composites and improve their photocatalytic properties. However, the high interfacial energy barrier limits the formation and nano-assembly of the heterogeneous junctions between MOFs and metal sulphides. Herein, the heterostructured Zr-MOF-S@CdS are successfully constructed through a sequential synthesis method, in which the mesoporous Zr-MOF are firstly decorated with thioglycolic acid through pore functionalization, and followed by the S2- anion exchange process resulting in the surface close attached growth of CdS onto Zr-MOF-S materials. Due to the presence of molecules linkers, the CdS can be precisely decorated onto Zr-MOF-S without aggregation, which can provide more active sites. Moreover, the intimate connections and the suitable band structures between two materials can also facilitate the photogenerated electron-hole pairs separation. Therefore, the resulting Zr-MOF-S@CdS with appropriate ratio exhibits high photocatalytic activity for water reduction, in which the H2 evolution rate can reach up to 1861.7 μmol·g‒1·h‒1, 4.5 times higher than pure CdS and 2.3 times higher than of Zr-MOF/CdS, respectively. Considering the promising future of MOF-based photocatalysts, this work may provide an avenue for the further design and synthesis MOF-based composite photocatalysts for efficient H2 evolution.

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Electrochemical creation of surface charge transfer channels on photoanodes for efficient solar water splitting Zhiwei Li, Huiting Huang, Wenjun Luo, Yingfei Hu, Rongli Fan, Zhi Zhu, Jun Wang, Jianyong Feng, Zhaosheng Li, Zhigang Zou 2022, 43 (9):  2342-2353.  DOI: 10.1016/S1872-2067(21)63986-4 Abstract ( 381 )   HTML ( 12 )   PDF (6417KB) ( 211 )   Supporting Information Electrochemical treatment is a popular and efficient method for improving the photoelectrochemical performance of water-splitting photoelectrodes. In our previous study, the electrochemical activation of Mo-doped BiVO4 electrodes was ascribed to the removal of MoOx segregations, which are considered to be surface recombination centers for photoinduced electrons and holes. However, this proposed mechanism cannot explain why activated Mo-doped BiVO4 electrodes gradually lose their activity when exposed to air. In this study, based on various characterizations, it is suggested that electrochemical treatment not only removes partial MoOx segregations but also initiates the formation of HyMoOx surface defects, which provide charge transfer channels for photogenerated holes. The charge separation of the Mo-doped BiVO4 electrode was significantly enhanced by these charge transfer channels. This study offers a new insight into the electrochemical activation of Mo-doped BiVO4 photoanodes, and the new concept of surface charge transfer channels, a long overlooked factor, will be valuable for the development of other (photo)electrocatalytic systems.

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Multiple carbon interface engineering to boost oxygen evolution of NiFe nanocomposite electrocatalyst Yuyan Qiao, Yanqiu Pan, Jiangwei Zhang, Bin Wang, Tingting Wu, Wenjun Fan, Yucheng Cao, Rashid Mehmood, Fei Zhang, Fuxiang Zhang 2022, 43 (9):  2354-2362.  DOI: 10.1016/S1872-2067(21)63916-5 Abstract ( 190 )   HTML ( 8 )   PDF (1634KB) ( 166 )   Supporting Information Interface engineering has been widely investigated to regulate the structure and performance of electrodes and photoelectrodes, but the investigation of multiple carbon interface modifications on the electrocatalytic oxygen evolution reaction (OER) is still shortage. Herein, we report remarkable promotion of OER performance on the NiFe-based nanocomposite electrocatalyst via the synergy of multiple carbon-based interface engineering. Specifically, carbon nanotubes were in situ grown on carbon fiber paper to improve the interface between CFP and NiFeOxHy, and graphite carbon nanoparticles were in situ loaded and partly doped into the NiFeOxHy to modify the intergranular interface charge transfer and electronic structure of NiFeOxHy. Consequently, the as-obtained NiFeOxHy-C/CNTs/CFP catalyst exhibited significantly enhanced electrocatalytic OER activity with an overpotential of 202 mV at 10 mA cm-2 in 1 mol L-1 KOH. Our work not only extends application of carbon materials but also provides an alternative strategy to develop highly efficient electrocatalysts.

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Progress and prospects of photocatalytic conversion of low-concentration NOx Nan Li, Chuanyi Wang, Ke Zhang, Haiqin Lv, Mingzhe Yuan, Detlef W. Bahnemann 2022, 43 (9):  2363-2387.  DOI: 10.1016/S1872-2067(22)64139-1 Abstract ( 277 )   HTML ( 20 )   PDF (33365KB) ( 213 )   NOx can cause severe environmental problems such as acid rain and photochemical smog, endangering human health and the living environment. Among them, NO pollution accounts for about 95%. NO can exist stably in the air for a long time when the concentration is lower than the ppm level. Therefore, the conversion of low concentration of NO has attracted more and more attention. However, traditional physical or chemical methods are difficult to deal with low concentration of NO, having high requirements on equipment and being not cost-effective. Semiconductor photocatalytic technology can convert low concentration of NO into non-toxic products and reduce its harm. This work briefly surveys the commonly used materials, modification methods, and mechanisms for semiconductor photocatalytic conversion of low concentration of NO. In addition, the challenges and prospects of ppb level of NO treatment are also discussed, aiming to promote the development of semiconductor photocatalytic conversion of NO.

Communication

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Visible-light photoredox-catalyzed selective carboxylation of C(sp2)-F bonds in polyfluoroarenes with CO2 Zhi-Yu Bo, Si-Shun Yan, Tian-Yu Gao, Lei Song, Chuan-Kun Ran, Yi He, Wei Zhang, Guang-Mei Cao, Da-Gang Yu 2022, 43 (9):  2388-2394.  DOI: 10.1016/S1872-2067(22)64140-8 Abstract ( 230 )   HTML ( 11 )   PDF (1156KB) ( 233 )   Supporting Information Visible light-driven carboxylation with CO2 have emerged as a sustainable and powerful way to transfer waste to treasure. However, it is still challenging for aryl fluorides due to the low reactivities of both C(sp2)-F bonds and CO2. Herein, we report the first photocatalytic carboxylation of aryl C-F bonds with CO2. The visible-light photoredox catalysis enables selective carboxylation of strong C(sp2)-F bonds in diverse polyfluoroarenes, such as penta-, tetra-, and tri-fluoroarenes under mild conditions, providing a facile access to a series of important polyfluoroaryl carboxylic acids with good yields. In contrast to previous reports of direct capture of polyfluoroaryl radicals, mechanistic studies suggest that the reduction of fleeting polyfluoroaryl radicals into polyfluoroaryl anions might be involved in this transformation, which may open a new avenue for photocatalytic functionalization of aryl C-F bonds.

Articles

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Thiazolo[5,4-d]thiazole-based covalent organic framework microspheres for blue light photocatalytic selective oxidation of amines with O2 Fulin Zhang, Xia Li, Xiaoyun Dong, Huimin Hao, Xianjun Lang 2022, 43 (9):  2395-2404.  DOI: 10.1016/S1872-2067(22)64127-5 Abstract ( 256 )   HTML ( 8 )   PDF (4413KB) ( 310 )   Supporting Information Covalent organic frameworks (COFs) with photoactive units have attracted significant interest in visible light photocatalysis and can present a metal-free scenario for activating O2. As a typical photoactive unit, thiazolo[5,4-d]thiazole (TzTz) has rarely been added to COFs. However, circumventing the low reversibility of TzTz, it could be embedded into the building blocks beforehand, along with other bonds like β-ketoenamine in forming COFs. TzTz was embedded into 1,1′-biphenyl-4,4′-diamine (BD) using this approach to produce 4,4′-(TzTz-2,5-diyl)dianiline (DTz). Under organobase-modulated solvothermal conditions, combining 1,3,5-triformylphloroglucinol (Tp) with BD and DTz resulted in the production of β-ketoenamine-linked TpBD-COF and TpDTz-COF. Both TpDTz-COF and TpBD-COF are microspheres. TpDTz-COF possessed more adequate separation and charge migration than TpBD-COF. This resulted in superior performance for the blue light photocatalytic selective oxidation of benzylamine with O2. Furthermore, with O2 as the main oxidant, a wealth of benzylamines could be converted into imines over TpDTz-COF. Mechanistic investigations substantiate that oxidation of benzylamines obeys an electron transfer pathway, in which superoxide anion (O2•-) is the crucial reactive oxygen species. This study highlights the superiority of TzTz-embedded COFs in developing effective photocatalytic systems for organic transformations.

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Pyrrolic N or pyridinic N: The active center of N-doped carbon for CO2 reduction Yu Shang, Yunxuan Ding, Peili Zhang, Mei Wang, Yufei Jia, Yunlong Xu, Yaqing Li, Ke Fan, Licheng Sun 2022, 43 (9):  2405-2413.  DOI: 10.1016/S1872-2067(22)64122-6 Abstract ( 974 )   HTML ( 27 )   PDF (2461KB) ( 421 )   Supporting Information Pyridinic N is widely regarded as the active center while pyrrolic N has low-activity in metal-free N-doped carbon for electrocatalytic CO2 reduction reaction (CO2RR) to CO, but this viewpoint remains open to question. In this study, through density functional theoretical calculations, we first illustrate that the intrinsic activity of pyrrolic N is high enough for effectively catalyzing CO2RR, however, due to the interplay with the neighboring pyridinic N sites, the activity of pyrrolic N is dramatically suppressed. Then, experimentally, metal-free N-doped carbon spheres (NCS) electrocatalysts without significant pyridinic N content are prepared for CO2RR. The pyrrolic N in NCS shows a direct-positive correlation with the performance for CO2RR, representing the active center with high activity. The optimum NCS could produce syngas with a wide range of CO/H2 ratio (0.09 to 12) in CO2RR depending on the applied potential, meanwhile, the best selectivity of 71% for CO can be obtained. Intentionally adding a small amount of pyridinic N to the optimum NCS dramatically decreases the activity for CO2RR, further verifying the suppressed activity of pyrrolic N sites by the neighboring pyridinic N sites. This work reveals the interaction between a variety of N species in N-doped carbon, and the potential of pyrrolic N as the new type of active site for electrocatalysts, which can improve our understanding of the electrocatalysis mechanism and be helpful for the rational design of high-efficient electrocatalysts.

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Hexanuclear ring cobalt complex for photochemical CO2 to CO conversion Xiangyu Meng, Rui Li, Junyi Yang, Shiming Xu, Chenchen Zhang, Kejia You, Baochun Ma, Hongxia Guan, Yong Ding 2022, 43 (9):  2414-2424.  DOI: 10.1016/S1872-2067(22)64144-5 Abstract ( 223 )   HTML ( 16 )   PDF (3781KB) ( 245 )   Supporting Information Photosynthesis in nature has been deemed as the most significant biochemical reaction, which maintains a relatively stable content of O2 and CO2 in the atmosphere. Herein, for a deeper comprehension of natural photosynthesis, an artificial photosynthesis model reaction of photochemical CO2 to CO conversion (CO2 +2 H+ + 2e- → CO + H2O) catalyzed by a homogeneous hexanuclear ring cobalt complex {K2[CoO3PCH2N(CH2CO2)2]}6 (Co6 complex) is developed. Using the [Ru(bpy)3]2+ as a photosensitizer and TEOA as a sacrificial electron donor, an optimal turnover frequency of 503.3 h‒1 and an apparent quantum efficiency of 0.81% are obtained. The good photocatalytic CO2 reduction performance is attributed to the efficient electron transfer between Co6 complex and [Ru(bpy)3]2+, which boosts the photogenerated carriers separation of the photosensitizer. It is confirmed by the j-V curves, light-assisted UV-vis curves, steady-state photoluminescence spectra and real-time laser flash photolysis experiments. In addition, the proposed catalytic mechanism for CO2 reduction reaction catalyzed by the Co6 complex is explored by the potassium thiocyanate poison experiment, Pourbaix diagram and density functional theory calculations.

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"All-in-one" covalent organic framework for photocatalytic CO2 reduction Dengmeng Song, Wenhua Xu, Jun Li, Jiale Zhao, Qing Shi, Fei Li, Xuzhuo Sun, Ning Wang 2022, 43 (9):  2425-2433.  DOI: 10.1016/S1872-2067(22)64143-3 Abstract ( 345 )   HTML ( 20 )   PDF (2443KB) ( 231 )   Supporting Information Constructed by selecting appropriate building blocks, covalent organic frameworks (COFs) can be endowed with a variety of specific functions. Herein, we successfully synthesized an imine-linked H2PReBpy-COF with the CO2 reduction catalyst [ReI(bpy)(CO)3Cl] and the porphyrin photosensitizer as the monomeric building units. The light-harvesting properties of the porphyrin itself, augmented by the extended π-conjugated planar structure of 2D COF, enable H2PReBpy-COF the excellent light-harvesting capability, efficient charge separation, and fast interfacial charge transfer. In addition, a large amount of uniformly distributed [ReI(bpy)(CO)3Cl] units offer H2PReBpy-COF an excellent activity toward photocatalytic CO2 reduction with moderate selectivity and reusability. This study demonstrated a proof of concept in which the advantages of COFs and functional monomers are rationally integrated for photocatalytic solar fuel conversion.

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Constructing oxygen vacancy-regulated cobalt molybdate nanoflakes for efficient oxygen evolution reaction catalysis Tingting Jiang, Weiwei Xie, Shipeng Geng, Ruchun Li, Shuqin Song, Yi Wang 2022, 43 (9):  2434-2442.  DOI: 10.1016/S1872-2067(22)64137-8 Abstract ( 529 )   HTML ( 34 )   PDF (7347KB) ( 341 )   Supporting Information Oxygen evolution reaction (OER) is the dominant step for plenty of energy conversion and storage technologies. However, the OER suffers from sluggish kinetics and high overpotential due to its complex 4-electron/proton transfer mechanism. Thus, developing efficient electrocatalysts is particularly urgent to accelerate OER catalysis but still remains a great challenge. Herein, we have synthesized the novel cobalt molybdate nanoflakes (CoMoO4-Ov-n@GF) with adjustable oxygen vacancies contents by in situ constructing CoMoO4 nanoflakes on graphite felt (GF) and annealing treatment under the reduction atmosphere. The best-performing CoMoO4-Ov-2@GF with optimal oxygen vacancies content shows splendid electrocatalytic performance with the low overpotential (296 mV at 10 mA cm‒2) and also small Tafel slope (62.4 mV dec‒1) in alkaline solution, which are comparable to those of the RuO2@GF. The experimental and the density functional theory calculations results reveal that the construction of optimal oxygen vacancies in CoMoO4 can expose more active sites, narrow the band-gap to increase the electrical conductivity, and modulate the free energy of the OER-related intermediates to accelerate OER kinetics, thus improving its intrinsic activity.

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Carbon dots-derived carbon nanoflowers decorated with cobalt single atoms and nanoparticles as efficient electrocatalysts for oxygen reduction Yaojia Cheng, Haoqiang Song, Jingkun Yu, Jiangwei Chang, Geoffrey I. N. Waterhouse, Zhiyong Tang, Bai Yang, Siyu Lu 2022, 43 (9):  2443-2452.  DOI: 10.1016/S1872-2067(22)64146-9 Abstract ( 237 )   HTML ( 11 )   PDF (3070KB) ( 219 )   Supporting Information The sluggish kinetics of oxygen reduction reaction (ORR) hinders the commercialization of Zn-air batteries (ZABs). Manipulating the electronic structure of electrocatalysts to optimize the adsorption energy of oxygen-containing intermediates during the 4e- ORR offers a practical route toward improving ORR kinetics. Herein, we designed a novel ORR electrocatalyst containing Co single atoms and nanoparticles supported by carbon dots-derived carbon nanoflowers (Co SAs/NPs CNF). Co SAs/NPs CNF possessed a very high ORR activity (E1/2 of the Co SAs/NPs CNF catalyst is 0.83 V (vs. RHE)), and outstanding catalytic performance and stability when used as the air-electrode catalyst in rechargeable ZABs (152.32 mW cm-2, 1000.58 mWh gZn-1, and over 1300 cycles at a current density of 5 mA cm-2). The Co SAs and Co NPs cooperated to improve electron and proton transfer processes during ORR. Theoretical calculations revealed that the presence of adjacent Co NPs optimized the electronic structure of the isolated Co-N4 sites, significantly lowering the energy barriers for the rate-determining step in ORR (adsorption of *OOH) and thereby delivering outstanding ORR performance. This work reveals that the combination of supported single-atom sites and metal nanoparticles can be highly beneficial for ORR electrocatalysis, outperforming catalysts containing only Co SAs or Co NPs.