Thermally reduced rGO-wrapped CoP/Co2P hybrid microflower as an electrocatalyst for hydrogen evolution reaction

Cobalt phosphides (CoPx) are potential candidates for use as high-efficiency hydrogen evolution reaction electrocatalysts that can replace noble metals, such as Pt. Typically, CoPx can be synthesized by phosphidation with Co-based precursors such as oxides or hydroxides. In this study, we propose a new strategy for synthesizing CoPx through the thermal reduction in cobalt phosphate (Co-3(PO4)(2)). A reduced graphene oxide-wrapped CoP/Co2P hybrid microflower was successfully synthesized by a facile coprecipitation method in a Co-3(PO4)(2) matrix, followed by a thermal reduction process. Co-3(PO4)(2) can be transformed to CoP/Co2P by treatment at 700 degrees C for 1hour, maintaining the original particle morphology with the assistance of reduced graphene oxide (rGO). In a 0.5mol/L H2SO4 solution, the rGO-CoP/Co2P microflower catalyzes the hydrogen evolution reaction with an overpotential of 156 mV at a current density of 10mA cm(-2), a Tafel slope of 53.8mV dec(-1), and good stability as observed through long-term CV and chronoamperometry tests.