Engineering Hierarchical‐Dimensional Co(OH)F into CoP Superstructure for Electrocatalytic Water Splitting

Abstract Multi‐dimensional materials can combine the advantages of fast mass diffusion of high dimensional structures and advanced intrinsic properties of low dimensional substructures. In specific, superstructures are widely prepared from assembling low dimensional materials into arrays by complicated methods. We recently proposed the concept of hierarchical‐dimensional material (HDM), in which superstructure is composed of low dimensional substructures from simple wet chemical method. Herein, we report the synthesis of a CoP HDM from the engineering of the hierarchical‐dimensional Co(OH)F precursor by successive phosphorization and acid etching. The resulting CoP superstructure is built by porous CoP rod substructure. The rods weave together to form 2D mesh plates and the 2D mesh plates stack together to form the 3D superstructure. Thus, a very interesting structure is generated with 0D, 1D, 2D and 3D features. The CoP material displayed outstanding electrocatalytic activity for both HER and OER in alkaline solutions. The overpotentials required to drive a HER and OER current density of 10 mA/cm 2 were 94 mV and 295 mV, respectively. The superior performance is believed to be associated with the unique structure from phosphorus‐based engineering of nanostructure.