The oxidized platinum (Pt) can exhibit better electrocatalytic activity than metallic Pt 0 in the hydrogen evolution reaction (HER), which has aroused great interest in exploring the role of oxygen in Pt-based catalysts. Herein, we select two structurally well-defined polyoxometalates Na 5 [H 3 Pt (IV) W 6 O 24 ] (PtW 6 O 24 ) and Na 3 K 5 [Pt (II) 2 (W 5 O 18 ) 2 ] (Pt 2 (W 5 O 18 ) 2 ) as the platinum oxide model to investigate the HER performance. Electrocatalytic experiments show the mass activities of PtW 6 O 24 /C and Pt 2 (W 5 O 18 ) 2 /C are 20.175 A mg −1 and 10.976 A mg −1 at 77 mV, respectively, which are better than that of commercial 20% Pt/C (0.398 A mg −1 ). The in situ synchrotron radiation experiments and DFT calculations suggest that the elongated Pt-O bond acts as the active site during the HER process, which can accelerate the coupling of proton and electron and the rapid release of H 2 . This work complements the knowledge boundary of Pt-based electrocatalytic HER, and suggests another way to update the state-of-the-art electrocatalyst.

Molybdenum carbides are considered as one type of privileged noble-metal-free electrocatalysts for hydrogen evolution reactions (HER) due to their d-band electron structure, which is similar to Pt. Especially, the electronic structure of such materials can be further adjusted by elemental doping to improve their electrocatalytic activity. Herein, we selected the Anderson-type polyoxometalates (POMs) (NH4)n[TMMo6O24H6]·5H2O (TM = Ni2+, Co2+, n = 4; TM = Fe3+, Cr3+, n = 3) as precursors to prepare new transition-metal-doped Mo2C materials. When these POMs were mixed with dicyandiamide (DCA) by solid grinding, and carbonized at a high temperature, a series of Ni-, Co-, Fe-, and Cr-doped Mo2C composite nanoparticles covered by few-layer graphitic carbon shells (abbr. TM-Mo2C@C) were obtained. All these nanoparticles possess a similar size, morphology, and TM/Mo component ratio, and thus it is feasible to systematically investigate the influence of different TM dopants on the electrocatalytic activity of Mo2C for HER. Both electrocatalytic experiments and DFT calculations reveal that TM dopants have a significant effect on the hydrogen binding energy (ΔGH*) and the catalytic activity of Mo2C. The sequence of HER electrocatalytic activity is as follows: Ni-Mo2C > Co-Mo2C > Fe-Mo2C > Cr-Mo2C. As a result, Ni-Mo2C@C possesses the best HER performance, which required an overpotential of 72 mV at a current density of 10 mA cm-2 and the Tafel slope is 65.8 mV dec-1. This work suggests a shortcut to reasonably investigate the effects of elemental doping on molybdenum carbides and explore new high-efficient and low-cost electrocatalysts for HER.

The hydrogen evolution reaction (HER) produces clean hydrogen through an electrochemical process. However, new nonprecious-metal electrocatalysts for the HER are required to reduce the consumption of energy. Herein, we report a new Co P/WC nano-heterojunction that consists of Co P and WC composite phases coated with a few-layer N-doped graphitic carbon shells (Co P/WC@NC). The composite was prepared by a one-step annealing of the polyoxometalate Na (NH ) [{(B-α-PW O )Co (OH)(H O) (Ale)} Co]⋅35 H O (Co P W ) and dicyandiamide (DCA). The preparation method consisted of the simultaneous phosphorization of Co and carbonization of W in a confined space to isolate a Co P/WC nano-heterojunction phase for the first time. Co P/WC@NC facilitated the generation of hydrogen in the electrolysis process, which had an overpotential of only 91 mV at a current density of 10 mA cm in the acid solution; an excellent HER performance (2 H +2 e →H ) and Tafel slope (40 mV dec ) as well as durability over a period of 50 h were achieved. Theoretical calculations showed that the Co P, WC, and N C dopants in the material synergistically promoted the HER activity rather than the individual constituents. Furthermore, Co P/WC@NC nano-heterojunctions showed good HER performance in the whole pH range of electrolytes and considerable durability in acidic media containing transition metal ions, which may attract more attention for the exploration and optimization of nano-heterojunction catalysts for the HER.

H2O2 plays an irreplaceable role in many aspects of human society, such as paper bleaching, medical disinfection, wastewater treatment, organic synthesis, hydrometallurgy and the electronic industry. However, the unsustainability of the current industrial production process of traditional anthraquinone has a serious conflict with the green sustainable development. The photo/electrocatalytic H2O2 production from renewable energy has the advantages of being more economical, low‐carbon and green, and in line with the requirements of energy economy. These catalytic methods of green H2O2 production have played a demonstrative role in the development of many small molecules, contributing to a fundamental understanding of general catalysis and providing a scientific perspective for future new energy cycles. In this review, the authors aim to integrate the reaction process and mechanism of photocatalytic and electrocatalytic H2O2 production, summarize the development and application of photocatalytic and electrocatalytic H2O2 production in recent years, and assess the modern technologies promoted in the process of H2O2 production research, including the development of flux production equipment and reaction coproduction, etc. This review intends to provide a clear logic profile and new directions for the development of H2O2 production, and calls for more researchers to provide more insights into the development of this field.

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