Construction of CoP/NiCoP Nanotadpoles Heterojunction Interface for Wide pH Hydrogen Evolution Electrocatalysis and Supercapacitor

Constructing well defined nanostructures is promising but still challenging for high-efficiency catalysts for hydrogen evolution reaction (HER) and energy storage. Herein, utilizing the differences in surface energies between (111) facets of CoP and NiCoP, a novel CoP/NiCoP heterojunction is designed and synthesized with a nanotadpoles (NTs)-like morphology via a solid-state phase transformation strategy. By effective interface construction, the disorder in terms of electronic structure and coordination environment at the interface in CoP/NiCoP NTs is created, which leads to dramatically elevated HER performance within a wide pH range. Theoretical calculations prove that an optimized proton chemisorption and H2O dissociation are achieved by an optimized phosphide polymorph at the interface, accelerating the HER reaction. The CoP/NiCoP NTs are also proved to be excellent candidates for use in supercapacitors (SCs) with a high specific capacitance (1106.2 F g(-1) at 1 A g(-1)) and good cycling stability (nearly 100% initial capacity retention after 1000 cycles). An asymmetric supercapacitor shows a high energy density (145 F g(-1) at 1 A g(-1)) and good cycling stability (capacitance retention is 95% after 3200 cycles). This work provides new insights into the catalyst design for electrocatalytic and energy storage applications.