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Nano and single‐atom catalysis open new possibilities of producing green hydrogen (H2) by water electrolysis. However, for the hydrogen evolution reaction (HER) which occurs at a characteristic reaction rate proportional to the potential, the fast generation of H2 nanobubbles at atomic‐scale interfaces often leads to the blockage of active sites. Herein, a nanoscale grade‐separation strategy is proposed to tackle mass‐transport problem by utilizing ordered three‐dimensional (3d) interconnected sub‐5 nm pores. The results reveal that 3d criss‐crossing mesopores with grade separation allow efficient diffusion of H2 bubbles along the interconnected channels. After the support of ultrafine ruthenium (Ru), the 3d mesopores are on a superior level to two‐dimensional system at maximizing the catalyst performance and the obtained Ru catalyst outperforms most of the other HER catalysts. This work provides a potential route to fine‐tuning few‐nanometer mass transport during water electrolysis. [ABSTRACT FROM AUTHOR]

Owing to their unique porous structure, metal‐organic framework (MOF) nanosheets are considered one of the best active materials for high‐performance electrocatalysts. Ultrathin nanosheet Ni−MOF assemblies, [Ni3(OH)2(C8H4O4)2(H2O)4] ⋅ 2H2O, were synthesized by using a simple solvothermal method and used for efficiently catalyzing ascorbic acid (AA) in a common phosphate buffer solution (PBS, pH=7.2). Electrochemical data analysis revealed good catalytic activity performance and outstanding stability for the AA oxidation reaction. The reason for analyzing its intrinsic may depend on the structure of the ultrathin nanosheet. This structure not only provides a pathway for improving electrocatalytic performance, but its special aggregation state also makes it more stable in electrocatalytic AA. Vitamin electrocatalysis: Ultrathin nanosheet Ni‐metal organic framework assemblies are regarded as very promising electrocatalysts when used for catalyzing ascorbic acid (AA). Electrochemical data analysis reveals good catalytic activity performance and outstanding stability for the AA oxidation reaction. The ultrathin nanosheet structure not only provides a pathway for improving electrocatalytic performance, but its special aggregation state also makes it more stable in electrocatalytic AA. [ABSTRACT FROM AUTHOR]

Hollow cobalt oxide is phosphated under an inert atmosphere to form a composite with interconnected porous structures. As an electrocatalyst for oxygen evolution reaction, the catalytic activity of this material is significantly better than Co 3 O 4. [Display omitted] • Amorphous porous CoP x -CoO y complex was constructed by low temperature phosphating. • The same structure was obtained when the method is applied to other oxides. • The structure can significantly increase the number of active sites required for OER. • The catalytic activity of the material for oxygen release reaction was better than that of Co 3 O 4. Interconnected porous structures and amorphous materials are widely used in the field of electrocatalysis owing to their rich catalytic active sites. Amorphous CoP x -CoO y composites with interconnected porous structures were constructed through low-temperature phosphating of cobalt oxides. Moreover, low-temperature phosphating of cobalt oxide and other metal oxides with different morphologies also produced the same porous structures, further proving the generality of this method. Interestingly, the prepared CoP x -CoO y catalyst has excellent electrocatalytic activity for oxygen evolution reactions in alkaline media. At a current density of 10 mA cm−2, an overpotential of 322 mV and a Tafel slope of 102 mV dec-1 are generated. In a 1 M KOH electrolyte, its electrochemical activity is significantly better than that of unphosphorylated Co 3 O 4. Under catalytic conditions, the excellent performance arises from the formation of the incorporation of phosphorus, amorphous phase and porous structures. The unique structure can provide a large number of active sites, significantly shortening the electron transfer pathway. This is the foundation of our research on the development of electrocatalysts with rich active sites. The synthesis of amorphous interconnected porous structures by introducing phosphorus will allow the application of high-efficiency catalysts in electrocatalysis and other important chemical reactions. [ABSTRACT FROM AUTHOR]

The development of efficient oxygen evolution reaction (OER) electrocatalysts is critical to overcome the efficiency bottleneck in hydrogen generation via water electrolysis. Hollow nanostructured materials have emerged as a hot topic for electrocatalysis research because of their advantages, including abundant active sites, a large contact area between the catalyst and the electrolyte, and a short transmission path. As highly efficient and stable OER electrocatalysts, cobalt‐based nanostructured materials have attracted more and more attention. In this work, cobalt metal/cobalt phosphides/nitrogen‐doped carbon composites (Co‐CoxP/NC) with a hierarchical hollow structure are designed by using hollow ZIF‐67 microspheres as precursors. By coating ZIF‐8 on the surface of hollow ZIF‐67 microspheres and further carbonizing, carbon nanowhiskers are successfully formed on the surface of hollow carbon spheres under the catalytic effect of Co nanoparticles at a high temperature. In the subsequent phosphating process, solid Co nanocrystalline particles are transformed into core–shell CoP and Co2P nanoparticles on account of the Kirkendall effect. Through the optimization of the microstructure of the material and the synergistic effect of transition metal, transition metal phosphide, and nitrogen doping, the overpotential of the optimal material is only 287 mV at 10 mA cm−2 current density in 1 m KOH. [ABSTRACT FROM AUTHOR]