Interfacial Electronic Coupling of Ultrathin Transition-Metal Hydroxides Nanosheets with Layered MXene as a New Prototype for Platinum-Like Hydrogen Evolution

Metal hydroxides and oxides have emerged as fascinating materials and key structures for electrocatalysis, but they are rarely investigated for HER. Herein, we introduce unique transition-metal hydroxides@MXene (TMHs@MXene) hybrids, including Co(OH)2@MXene, Ni(OH)2@MXene, and FeOOH@MXene, with well-defined components and hierarchical sheet-like architectures for alkaline HER. By virtue of the novel structure and strong interfacial interaction between transition-metal hydroxides (TMHs) and MXene nanosheets, the obtained nanohybrids not only provide sufficient active sites and robust structure, but also ensure favourable electrochemical kinetic and superior catalytic activity. Significantly, both theoretical calculations and electrochemical test prove that the interfacial electronic coupling between the two different components could optimize the adsorption energy of water and hydrogen, thereby resulting in Pt-like catalytic activity including low Tafel slope (31.7 mV dec-1), small overpotential (21.0 mV@10 mA cm-2), and excellent stability for Co(OH)2@MXene. As expected, an alkaline water electrolyzer is built using Co(OH)2@MXene cathode for overall water splitting, which achieves a current density of 10 mA cm-2 at 1.46 V with outstanding stability over 100 h. Our discovery highlights the great potential of interfacial electronic coupling to optimize the advanced electrocatalysts for application in energy-related fields.