Controllable synthesis of Co2P nanorods as high-efficiency bifunctional electrocatalyst for overall water splitting

Abstract

One-dimensional transition metal phosphides with large specific surface areas and efficient conductivity have the great potential in both hydrogen and oxygen evolution reaction (HER and OER) as bifunctional catalysts, which are at the heart of water splitting. Herein, we firstly report the controllable synthesis of Co2P nanorods through a substrate- and template-free facile phosphating reaction. Electrochemical test results reveal that the synthesized Co2P nanorods exhibit superior bifunctional activity with overpotentials of 87 mV for HER and 310 mV for OER at 10 mA cm−2, respectively, relative to Co2P/CoP branched nanostructure, CoP nanoparticles and commercial Co2P in alkaline media. In addition, the bifunctional Co2P nanorods catalysts enable overall water splitting with a cell voltage of 1.65 V to achieve 10 mA cm−2 and stabilized potentials at different current densities testing over 24 h. Further analysis demonstrate that the remarkably bifunctional activity is contributed to high charge transfer efficiency, large contact area with electrolyte and a large number of exposed active sites provided by the rod-like nanostructure. This work should shed light on an industrialized pathway for the future design of phosphide catalysts to apply to overall water splitting even other emerging energy devices.