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Chinese Journal of Catalysis
2021, Vol. 42, No. 11
Online: 18 November 2021

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Cover: Prof. Zhang and coworkers in their article on pages 1983–1991reported a water-involving electrochemical transfer hydrogenation and dehydrogenation of N-heterocycles. Self-supported MoNi4 alloy is designedly synthesized as the bifunctional electrode enabling the transfer hydrogenation of unsaturated N-heterocycles using the active hydrogen atom (H*) and the oxidative dehydrogenation of saturated N-heterocycles using the in situ formed NiIII species from water electrolysis.

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Lignin valorization toward value-added chemicals and fuels via electrocatalysis: A perspective Chenxin Yang, Henan Chen, Tao Peng, Baiyao Liang, Yun Zhang, Wei Zhao 2021, 42 (11):  1831-1842.  DOI: 10.1016/S1872-2067(21)63839-1 Abstract ( 578 )   HTML ( 282 )   PDF (5068KB) ( 604 )   Developing efficient approaches for lignin upgrading is of interest for the industrial production of chemicals and fuels from renewable biomass. Electrocatalytic lignin upgrading powered by renewable electricity operating under gentle conditions (at or near ambient pressures and temperatures) enables a decentralized production of chemicals and fuels. Herein, we will cover the structures of lignin and review the recent advances in the electrocatalytic lignin upgrade, the electrocatalytic depolymerization of lignin, and the electrocatalytic upgrading of lignin monomers to value-added chemicals and fuels. Finally, we provide insights into the main challenges and future perspectives of this field.

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Hollow and substrate-supported Prussian blue, its analogs, and their derivatives for green water splitting Jing-Yi Xie, Bin Dong 2021, 42 (11):  1843-1864.  DOI: 10.1016/S1872-2067(21)63833-0 Abstract ( 346 )   HTML ( 32 )   PDF (6147KB) ( 382 )   To meet the current energy needs of society, the highly efficient and continuous production of clean energy is required. One of the key issues facing the green hydrogen evolution is the construction of efficient, low-cost electrocatalysts. Prussian blue (PB), Prussian blue analogs (PBAs), and their derivatives have tunable metal centers and have attracted significant interest as novel photo- and electrochemical catalysts. In this review, recent research progress into PB/PBA-based hollow structures, substrate-supported nanostructures, and their derivatives for green water splitting is discussed and summarized. First, several remarkable examples of nanostructured PB/PBAs supported on substrates (copper foil, carbon cloth, and nickel foam) and hollow structures (such as single-shelled hollow boxes, open hollow cages, and intricate hollow structures (multi-shell and yolk-shell)) are discussed in detail, including their synthesis and formation mechanisms. Subsequently, the applications of PB/PBA derivatives ((hydr)oxides, phosphides, chalcogenides, and carbides) for water splitting are discussed. Finally, the limitations in this research area and the most urgent challenges are summarized. We hope that this review will stimulate more researchers to develop technologies based on these intricate PB/PBA structures and their derivatives for highly efficient, green water splitting.

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Radical denitrogenative transformations of polynitrogen heterocycles: Building C-N bonds and beyond Wen-Chao Yang, Cai-Yun Chen, Jun-Feng Li, Zu-Li Wang 2021, 42 (11):  1865-1875.  DOI: 10.1016/S1872-2067(21)63814-7 Abstract ( 418 )   HTML ( 15 )   PDF (1256KB) ( 285 )   Polynitrogen heterocycles are readily available and have recently arisen as versatile synthons for the formation of various C-C and C-X bonds, and medicinally active nitrogen-containing heterocycles. Several cascade reactions, including annulation, radical cascade, and borylation reactions, have been reported in which polynitrogen heterocycles are applied as arylation reagents. The success of these exceptional reactions illustrates the great synthetic potential of polynitrogen heterocycles, which provides a direct and useful approach to arylation reactions and the synthesis of nitrogen-containing heterocycles. The use of photocatalysts to effectively transfer energy from visible light to non-absorbing compounds has gained increasing attention as this method allows for the mild and efficient generation of radicals in a controlled manner. This approach has thus led to new methods that involve unique bond formation reactions. In addition, the use of free radical intermediates stabilized by transition metal catalysts is a powerful way to construct new chemical bonds. The aim of this review is to highlight the rapidly expanding area of radical-initiated denitrogenative cascade reactions of polynitrogen heterocycles and elaborate on their mechanisms from a new perspective by using photocatalysis and metal-based catalysis.

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Strategies on improving the electrocatalytic hydrogen evolution performances of metal phosphides Wenli Yu, Yuxiao Gao, Zhi Chen, Ying Zhao, Zexing Wu, Lei Wang 2021, 42 (11):  1876-1902.  DOI: 10.1016/S1872-2067(21)63855-X Abstract ( 321 )   HTML ( 26 )   PDF (9969KB) ( 684 )   Among the sustainable energy sources, hydrogen is the one most promising for alleviating the pollution issues related to the usage of conventional fuels, as it can be produced in an efficient and eco-friendly way via electrocatalytic water splitting. The hydrogen evolution reaction (HER, a half-reaction of water splitting) plays a pivotal role in decreasing the price and increasing the catalytic efficiency of hydrogen production and is efficiently promoted by metal phosphides in different electrolytes. Herein, we summarize the recent advances in the development of metal phosphides as HER electrocatalysts, focus on their synthesis (post-treatment, in situ generation, and electrodeposition methods) and the enhancement of their electrocatalytic activity (via elemental doping, interface and vacancy engineering, construction of specific supports and nanostructures, and the design of bi- or polymetallic phosphides), and highlight the crucial issues and challenges of future development.

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Improving the performance of metal-organic frameworks for thermo-catalytic CO2 conversion: Strategies and perspectives Leiduan Hao, Qineng Xia, Qiang Zhang, Justus Masa, Zhenyu Sun 2021, 42 (11):  1903-1920.  DOI: 10.1016/S1872-2067(21)63841-X Abstract ( 341 )   HTML ( 15 )   PDF (6278KB) ( 380 )   Climate change caused by the increasing emission of CO2 to the atmosphere has become a global concern. To ameliorate this issue, converting CO2 into valuable chemicals is highly desirable, enabling a sustainable low-carbon future. To this end, developing efficient catalytic systems for CO2 conversion has sparked intense interests from both academia and industry. Taking advantage of their highly porous structures and unique properties, metal-organic frameworks (MOFs) have shown great potential as heterogeneous catalysts for CO2 conversion. Various transformations involving CO2 have been accomplished over MOFs-based materials. Here we provide a comprehensive and up-to-date review on recent advances of heterogeneous CO2 thermocatalysis using MOFs, highlighting relationships between structures and properties. Special attention is given to the design strategies for improving the catalytic performance of MOFs. Avenues available to enrich the catalytic active sites in MOF structures are stressed and their respective impacts on CO2 conversion efficiency are presented. The synergistic effects between each active site within the structure of MOFs and derivatives are discussed. In the end, future perspectives and challenges in CO2 conversion by heterogeneous catalysis with MOFs are described.

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Photo-/electrocatalytic functionalization of quinoxalin-2(1H)-ones Kai Sun, Fang Xiao, Bing Yu, Wei-Min He 2021, 42 (11):  1921-1943.  DOI: 10.1016/S1872-2067(21)63850-0 Abstract ( 401 )   HTML ( 17 )   PDF (1829KB) ( 366 )   The photo-/electrocatalytic functionalization of quinoxalin-2(1H)-ones has emerged as a promising and powerful approach for post-synthetic modification of quinoxalin-2(1H)-ones. This review provides an overview of recent developments in photo-/electrocatalytic functionalization of quinoxalin-2(1H)-ones including arylation, alkylation, fluoroalkylation, amination, phosphorylation, acylation, alkoxylation, thiolation, silylation, and annulation. The reaction scope and the related mechanism are also well discussed.

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Layered double hydroxide photocatalysts for solar fuel production Kailin Wang, Tianqi Wang, Quazi Arif Islam, Yan Wu 2021, 42 (11):  1944-1975.  DOI: 10.1016/S1872-2067(21)63861-5 Abstract ( 1039 )   HTML ( 46 )   PDF (8242KB) ( 609 )   Splitting water or reducing CO2 via semiconductor photocatalysis to produce H2 or hydrocarbon fuels through the direct utilization of solar energy is a promising approach to mitigating the current fossil fuel energy crisis and environmental challenges. It enables not only the realization of clean, renewable, and high-heating-value solar fuels, but also the reduction of CO2 emissions. Layered double hydroxides (LDHs) are a type of two-dimensional anionic clay with a brucite-like structure, and are characterized by a unique, delaminable, multidimensional, layered structure; tunable intralayer metal cations; and exchangeable interlayer guest anions. Therefore, it has been widely investigated in the fields of CO2 reduction, photoelectrocatalytic water oxidation, and water photolysis to produce H2. However, the low carrier mobility and poor quantum efficiency of pure LDH limit its application. An increasing number of scholars are exploring methods to obtain LDH-based photocatalysts with high energy conversion efficiency, such as assembling photoactive components into LDH laminates, designing multidimensional structures, or coupling different types of semiconductors to construct heterojunctions. This review first summarizes the main characteristics of LDH, i.e., metal-cation tunability, intercalated guest-anion substitutability, thermal decomposability, memory effect, multidimensionality, and delaminability. Second, LDHs, LDH-based composites (metal sulfide-LDH composites, metal oxide-LDH composites, graphite phase carbon nitride-LDH composites), ternary LDH-based composites, and mixed-metal oxides for splitting water to produce H2 are reviewed. Third, graphite phase carbon nitride-LDH composites, MgAl-LDH composites, CuZn-LDH composites, and other semiconductor-LDH composites for CO2 reduction are introduced. Although the field of LDH-based photocatalysts has advanced considerably, the photocatalytic mechanism of LDHs has not been thoroughly elucidated; moreover, the photocatalytic active sites, the synergy between different components, and the interfacial reaction mechanism of LDH-based photocatalysts require further investigation. Therefore, LDH composite materials for photocatalysis could be developed through structural regulation and function-oriented design to investigate the effects of different components and interface reactions, the influence of photogenerated carriers, and the impact of material composition on the physical and chemical properties of the LDH-based photocatalyst.

Communications

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Photo-thermal CO2 reduction with methane on group VIII metals: In situ reduced WO3 support for enhanced catalytic activity Huimin Liu, Xianguang Meng, Weiwei Yang, Guixia Zhao, Dehua He, Jinhua Ye 2021, 42 (11):  1976-1982.  DOI: 10.1016/S1872-2067(21)63835-4 Abstract ( 274 )   HTML ( 27 )   PDF (1706KB) ( 336 )   Supporting Information Photo-thermal CO2 reduction with methane (CRM) is beneficial for solar energy harvesting and energy storage. The search for efficient photo-thermal catalysts is of great significance. Here, we reveal that group VIII metal catalysts supported by optical material WO3 are more effective for photo-thermal CRM, giving catalytic activities with visible light assistance that are 1.4-2.4 times higher than that achieved under thermal conditions. The activity enhancement (1.4-2.4 times) was comparable to that achieved with plasmonic-Au-promoted catalysts (1.7 times). Characterization results indicated that WO3 was partially reduced to WO3-x in situ under the reductive CRM reaction atmosphere, and that WO3-x rather than WO3 enhanced the activities with visible light assistance. Our method provides a promising approach for improving the activity of catalysts under light irradiation.

Articles

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Water-involving transfer hydrogenation and dehydrogenation of N-heterocycles over a bifunctional MoNi4 electrode Mengyang Li, Cuibo Liu, Yi Huang, Shuyan Han, Bing Zhang 2021, 42 (11):  1983-1991.  DOI: 10.1016/S1872-2067(21)63834-2 Abstract ( 230 )   HTML ( 15 )   PDF (2334KB) ( 293 )   Supporting Information A room-temperature electrochemical strategy for hydrogenation (deuteration) and reverse dehydrogenation of N-heterocycles over a bifunctional MoNi4 electrode is developed, which includes the hydrogenation of quinoxaline using H2O as the hydrogen source with 80% Faradaic efficiency and the reverse dehydrogenation of hydrogen-rich 1,2,3,4-tetrahydroquinoxaline with up to 99% yield and selectivity. The in situ generated active hydrogen atom (H*) is plausibly involved in the hydrogenation of quinoxaline, where a consecutive hydrogen radical coupled electron transfer pathway is proposed. Notably, the MoNi4 alloy exhibits efficient quinoxaline hydrogenation at an overpotential of only 50 mV, owing to its superior water dissociation ability to provide H* in alkaline media. In situ Raman tests indicate that the NiII/NiIII redox couple can promote the dehydrogenation process, representing a promising anodic alternative to low-value oxygen evolution. Impressively, electrocatalytic deuteration is easily achieved with up to 99% deuteration ratios using D2O. This method is capable of producing a series of functionalized hydrogenated and deuterated quinoxalines.

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Metastable-phase β-Fe2O3 photoanodes for solar water splitting with durability exceeding 100 h Yang Li, Ningsi Zhang, Changhao Liu, Yuanming Zhang, Xiaoming Xu, Wenjing Wang, Jianyong Feng, Zhaosheng Li, Zhigang Zou 2021, 42 (11):  1992-1998.  DOI: 10.1016/S1872-2067(21)63822-6 Abstract ( 238 )   HTML ( 16 )   PDF (2250KB) ( 237 )   Supporting Information Planar films of pure and Ti4+-doped β-Fe2O3 were prepared by a spray pyrolysis method. X-ray diffraction patterns and Raman spectra of the metastable β-Fe2O3 film showed that its thermal stability was significantly improved because of covalent bonds in the interfaces between the film and substrate, while only weak Van der Waals bonds existed at the interfaces within the particle-assembled β-Fe2O3 film prepared by electrophoretic deposition. The as-prepared planar films were thus able to withstand higher annealing temperature and stronger laser irradiation power in comparison with the β-Fe2O3 particle-assembly. Ti4+ doping was used to increase the concentration of carriers in the metastable β-Fe2O3 film. Compared with pure β-Fe2O3 photoanodes, the highest saturated photocurrent for water splitting over the Ti4+-doped β-Fe2O3 photoanode was increased by a factor of approximately three. The β-Fe2O3 photoanode exhibited photochemical stability for water splitting for a duration exceeding 100 h, which indicates its important potential application in solar energy conversion.

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Ni(OH)2 quantum dots as a stable cocatalyst modified α-Fe2O3 for enhanced photoelectrochemical water-splitting Jiayue Rong, Zhenzhen Wang, Jiaqi Lv, Ming Fan, Ruifeng Chong, Zhixian Chang 2021, 42 (11):  1999-2009.  DOI: 10.1016/S1872-2067(21)63829-9 Abstract ( 174 )   HTML ( 11 )   PDF (4054KB) ( 191 )   Supporting Information Depositing a cocatalyst has proven to be an important strategy for improving the photoelectrochemical (PEC) water-splitting efficiency of photoanodes. In this study, Ni(OH)2 quantum dots (Ni(OH)2 QDs) were deposited in situ onto an α-Fe2O3 photoanode via a chelation-mediated hydrolysis method. The photocurrent density of the Ni(OH)2 QDs/α-Fe2O3 photoanode reached 1.93 mA·cm-2 at 1.23 V vs. RHE, which is 3.5 times that of α-Fe2O3, and an onset potential with a negative shift of ca. 100 mV was achieved. More importantly, the Ni(OH)2 QDs exhibited excellent stability in maintaining PEC water oxidation at a high current density, which is attributed to the ultra-small crystalline size, allowing for the rapid acceptance of holes from α-Fe2O3 to Ni(OH)2 QDs, formation of active sites for water oxidation, and hole transfer from the active sites to water molecules. Further (photo)electrochemical analysis suggests that Ni(OH)2 QDs not only provide maximal active sites for water oxidation but also suppress charge recombination by passivating the surface states of α-Fe2O3, thereby significantly enhancing the water oxidation kinetics over the α-Fe2O3 surface.

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Amide-linked covalent organic frameworks as efficient heterogeneous photocatalysts in water Si Ma, Ziping Li, Ji Jia, Zhenwei Zhang, Hong Xia, He Li, Xiong Chen, Yanhong Xu, Xiaoming Liu 2021, 42 (11):  2010-2019.  DOI: 10.1016/S1872-2067(21)63836-6 Abstract ( 587 )   HTML ( 27 )   PDF (2531KB) ( 525 )   Supporting Information Semiconductor photocatalysts play an indispensable role in the photocatalytic process. Two-dimensional covalent organic frameworks (2D-COFs), as a kind of innovative photocatalyst, have garnered tremendous attention. Herein, we report an amide-linked 2D-COF (COF-JLU19) with outstanding photocatalytic performance in water, designed through a multi-synergistic approach. The synergistic effects of the high porosity, photoactive framework, high wettability, and stability of COF-JLU19 led to an unprecedented enhancement in the photocatalytic activity and recyclability in water upon illumination by visible light. More importantly, amide-linked 2D-COF based electrospinning membranes were prepared, which also exhibited superior photocatalytic activity for the degradation of Rhodamine B in water with sunlight. This study highlights the potential of the multi-synergistic approach as a universal rule for developing COF-based photocatalysts to address environmental and energy challenges.

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Enhanced ambient ammonia photosynthesis by Mo-doped Bi5O7Br nanosheets with light-switchable oxygen vacancies Xue Chen, Ming-Yu Qi, Yue-Hua Li, Zi-Rong Tang, Yi-Jun Xu 2021, 42 (11):  2020-2026.  DOI: 10.1016/S1872-2067(21)63837-8 Abstract ( 216 )   HTML ( 15 )   PDF (2451KB) ( 264 )   Supporting Information The fabrication of efficient catalysts to reduce nitrogen (N2) to ammonia (NH3) is a significant challenge for artificial N2 fixation under mild conditions. In this work, we demonstrated that the simultaneous introduction of oxygen vacancies (OVs) and Mo dopants into Bi5O7Br nanosheets can significantly increase the activity for photocatalytic N2 fixation. The 1 mol% Mo-doped Bi5O7Br nanosheets exhibited an optimal NH3 generation rate of 122.9 μmol g-1 h-1 and durable stability, which is attributed to their optimized conduction band position, suitable absorption edge, large number of light-switchable OVs, and improved charge carrier separation. This work provides a promising approach to design photocatalysts with light-switchable OVs for N2 reduction to NH3 under mild conditions, highlighting the wide application scope of nanostructured BiOBr-based photocatalysts as effective N2 fixation systems.

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Encapsulated Ni-Co alloy nanoparticles as efficient catalyst for hydrodeoxygenation of biomass derivatives in water Dongdong Wang, Wanbing Gong, Jifang Zhang, Miaomiao Han, Chun Chen, Yunxia Zhang, Guozhong Wang, Haimin Zhang, Huijun Zhao 2021, 42 (11):  2027-2037.  DOI: 10.1016/S1872-2067(21)63828-7 Abstract ( 462 )   HTML ( 26 )   PDF (4738KB) ( 353 )   Supporting Information Catalytic hydrodeoxygenation (HDO) is one of the most promising strategies to transform oxygen-rich biomass derivatives into high value-added chemicals and fuels, but highly challenging due to the lack of highly efficient nonprecious metal catalysts. Herein, we report for the first time of a facile synthetic approach to controllably fabricate well-defined Ni-Co alloy NPs confined on the tip of N-CNTs as HDO catalyst. The resultant Ni-Co alloy catalyst possesses outstanding HDO performance towards biomass-derived vanillin into 2-methoxy-4-methylphenol in water with 100% conversion efficiency and selectivity under mild reaction conditions, surpassing the reported high performance nonprecious HDO catalysts. Impressively, our experimental results also unveil that the Ni-Co alloy catalyst can be generically applied to catalyze HDO of vanillin derivatives and other aromatic aldehydes in water with 100% conversion efficiency and over 90% selectivity. Importantly, our DFT calculations and experimental results confirm that the achieved outstanding HDO catalytic performance is due to the greatly promoted selective adsorption and activation of C=O, and desorption of the activated hydrogen species by the synergism of the alloyed Ni-Co NPs. The findings of this work affords a new strategy to design and develop efficient transition metal-based catalysts for HDO reactions in water.

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Effect of In2O3 particle size on CO2 hydrogenation to lower olefins over bifunctional catalysts Siyu Lu, Haiyan Yang, Zixuan Zhou, Liangshu Zhong, Shenggang Li, Peng Gao, Yuhan Sun 2021, 42 (11):  2038-2048.  DOI: 10.1016/S1872-2067(21)63851-2 Abstract ( 239 )   HTML ( 22 )   PDF (1893KB) ( 348 )   Supporting Information A reaction-coupling strategy is often employed for CO2 hydrogenation to produce fuels and chemicals using oxide/zeolite bifunctional catalysts. Because the oxide components are responsible for CO2 activation, understanding the structural effects of these oxides is crucial, however, these effects still remain unclear. In this study, we combined In2O3, with varying particle sizes, and SAPO-34 as bifunctional catalysts for CO2 hydrogenation. The CO2 conversion and selectivity of the lower olefins increased as the average In2O3 crystallite size decreased from 29 to 19 nm; this trend mainly due to the increasing number of oxygen vacancies responsible for CO2 and H2 activation. However, In2O3 particles smaller than 19 nm are more prone to sintering than those with other sizes. The results suggest that 19 nm is the optimal size of In2O3 for CO2 hydrogenation to lower olefins and that the oxide particle size is crucial for designing catalysts with high activity, high selectivity, and high stability.

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Intensified solar thermochemical CO2 splitting over iron-based redox materials via perovskite-mediated dealloying-exsolution cycles Yue Hu, Jian Wu, Yujia Han, Weibin Xu, Li Zhang, Xue Xia, Chuande Huang, Yanyan Zhu, Ming Tian, Yang Su, Lin Li, Baolin Hou, Jian Lin, Wen Liu, Xiaodong Wang 2021, 42 (11):  2049-2058.  DOI: 10.1016/S1872-2067(21)63857-3 Abstract ( 220 )   HTML ( 11 )   PDF (7885KB) ( 279 )   Supporting Information Solar thermochemical CO2-splitting (STCS) is a promising solution for solar energy harvesting and storage. However, practical solar fuel production by utilizing earth-abundant iron/iron oxides remains a great challenge because of the formation of passivation layers, resulting in slow reaction kinetics and limited CO2 conversion. Here, we report a novel material consisting of an iron-nickel alloy embedded in a perovskite substrate for intensified CO production via a two-step STCS process. The novel material achieved an unprecedented CO production rate of 381 mL g-1 min-1 with 99% CO2 conversion at 850 °C, outperforming state-of-the-art materials. In situ structural analyses and density functional theory calculations show that the alloy/substrate interface is the main active site for CO2 splitting. Preferential oxidation of the FeNi alloy at the interface (as opposed to forming an FeOx passivation shell encapsulating bare metallic iron) and rapid stabilization of the iron oxide species by the robust perovskite matrix significantly promoted the conversion of CO2 to CO. Facile regeneration of the alloy/perovskite interfaces was realized by isothermal methane reduction with simultaneous production of syngas (H2/CO = 2, syngas yield > 96%). Overall, the novel perovskite-mediated dealloying-exsolution redox system facilitates highly efficient solar fuel production, with a theoretical solar-to-fuel efficiency of up to 58%, in the absence of any heat integration.

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Zirconium-hydride-catalyzed site-selective hydroboration of amides for the synthesis of amines: Mechanism, scope, and application Bo Han, Jiong Zhang, Haijun Jiao, Lipeng Wu 2021, 42 (11):  2059-2067.  DOI: 10.1016/S1872-2067(21)63853-6 Abstract ( 240 )   HTML ( 14 )   PDF (2229KB) ( 387 )   Supporting Information Developing mild and efficient catalytic methods for the selective synthesis of amines is a longstanding research objective. In this respect, catalytic deoxygenative amide reduction has proven to be promising but challenging, as this approach necessitates selective C-O bond cleavage. Herein, we report the selective hydroboration of primary, secondary, and tertiary amides at room temperature catalyzed by an earth-abundant-metal catalyst, Zr-H, for accessing diverse amines. Various readily reducible functional groups, such as esters, alkynes, and alkenes, were well tolerated. Furthermore, the methodology was extended to the synthesis of bio- and drug-derived amines. Detailed mechanistic studies revealed a reaction pathway entailing aldehyde and amido complex formation via an unusual C-N bond cleavage-reformation process, followed by C-O bond cleavage.

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Electrodeposited PtNi nanoparticles towards oxygen reduction reaction: A study on nucleation and growth mechanism Lutian Zhao, Yangge Guo, Cehuang Fu, Liuxuan Luo, Guanghua Wei, Shuiyun Shen, Junliang Zhang 2021, 42 (11):  2068-2077.  DOI: 10.1016/S1872-2067(21)63860-3 Abstract ( 688 )   HTML ( 39 )   PDF (4656KB) ( 459 )   Supporting Information In this work, highly monodispersed Pt-Ni alloy nanoparticles were directly deposited on carbon substrate through a facile electrodeposition strategy in the solvent system of N,N-dimethylformamide (DMF). A series of carbon supported Pt-Ni alloy electrocatalysts were synthesized under different applied electrode potentials. Among all as-obtained samples, the Pt-Ni/C electrocatalyst deposited at -1.73 V exhibits the optimal specific activity up to 1.850 mA cm-2 at 0.9 V vs. RHE, which is 6.85 times higher than that of the commercial Pt/C. Comprehensive physiochemical characterizations and computational evaluations via density functional theory were conducted to unveil the nucleation and growth mechanism of PtNi alloy formation. Compared to the aqueous solution, DMF solvent molecule must not be neglected in avoiding particle agglomeration and synthesis of monodispersed nanoparticles. During the alloy co-deposition process, Ni sites produced through the reduction of Ni(II) precursor not only facilitates Pt-Ni alloy crystal nucleation but also in favor of further Pt reduction on the Ni-inserted Pt surface. As for the deposition potential, it adjusts the final particle size. This work provides a hopeful extended Pt-based catalyst layer production strategy for proton exchange membrane fuel cells and a new idea for the nucleation and growth mechanism exploration for electrodeposited Pt alloy.

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Constrained Al sites in FER-type zeolites Weifeng Chu, Xiaona Liu, Zhiqiang Yang, Hiroya Nakata, Xingzhi Tan, Xuebin Liu, Longya Xu, Peng Guo, Xiujie Li, Xiangxue Zhu 2021, 42 (11):  2078-2087.  DOI: 10.1016/S1872-2067(21)63884-6 Abstract ( 282 )   HTML ( 16 )   PDF (3487KB) ( 433 )   Supporting Information Crystallographic sites of Brönsted acids (Si-OH-Al) in zeolites, which are closely associated with the Al sites, play a significant and unique role in the catalytic application, especially when they are distributed in open channel systems or confined in cavities with small pore openings. In this article, we unraveled constrained Al crystallographic sites in FER-type zeolites containing the distinct local environments (10-ring channels and ferrierite cavities) by Rietveld refinement against the powder X-ray diffraction data. Final refinement demonstrates that regardless of the types of structure-directing agents and synthetic medium utilized, T1 and/or T3 are Al-rich positions, which are further confirmed by theoretical calculations. This new finding of constrained Al sites in the FER-type zeolite can well explain its limited catalytic activity in the DME carbonylation reaction.