A sandwich structure of cobalt pyrophosphate/nickel phosphite@C: one step synthesis and its good electrocatalytic performance.

Oxygen evolution reaction (OER) is the basic reaction to achieve water decomposition and hydrogen production. Here, an OER catalyst material, carbon-coated cobalt pyrophosphate/nickel phosphite (Co₂P₂O₇/Ni(PO₃)₂@C) composite with sandwich structure, was prepared in vacuum environment by a simple method, which not only simplified the traditional two-step phosphating process but also directly formed carbon layer from homologous carbon. The tests for OER showed that the Co₂P₂O₇/Ni(PO₃)₂@C composite had lower overpotential and Tafel slope as well as stable catalytic property in alkaline solution. In 1 M KOH, the composite exhibited the overpotential of 279 mV which was lower than that of commercial catalyst at a current density of 10 mA cm⁻², and its Tafel slope is 102 mV dec⁻¹. Due to the protection of the carbon layer, the composite exhibited good stability, so that the current density only decreased 3.9% after being cycled for 12 h. This study should help to obtain other stable electrocatalytic materials of transition metal compounds as OER catalysts. [ABSTRACT FROM AUTHOR]