Porous 2D cobalt–nickel phosphide triangular nanowall architecture assembled by 3D microsphere for enhanced overall water splitting

Abstract The development of bifunctional electrocatalysts with remarkable activity is highly desired for optimal application in overall water splitting, yet challenging. Herein, a unique CoNiP/NF catalyst with advanced feature of hollow well-integration nanostructure on porous Ni foam substrate is reported. Uniform and well-designed 2D cobalt‐based MOF nanosheet are prepared through a simple room temperature static growth, and then the 2D nanosheet arrays are converted into porous 2D nanosheets assembled by 3D microspheres due to ion-exchange and etching process with an additional phosphating. The as-obtained CoNiP/NF nanostructure arrays integrate the advantages of 2D nanosheets and 3D microspheres, modulating the intrinsic electronic structure and further providing rich reaction active sites, which not only promote the permeations of electrolyte, but also promote the evolution/release of gas. When CoNiP/NF as a flexible electrode for electrolysis of water, the nanowall arrays electrode shows remarkable electrochemical performance toward HER and OER with only 147 and 234 mV overpotential at 10 mA cm−2, respectively, and excellent cycle capability. Moreover, it delivers a much lower cell voltage of 1.62 V to attain 10 mA cm−2 as superior bifunctional electrocatalyst. Density functional theory (DFT) calculations suggest that the advantages of porous structure can facilitate fast electron transfer and mass transport, further improve electrochemical ability. It can be desired that this work reveals a rational technique to design porous nano-catalysts for hydrogen economy.