Three-dimensional amorphous N-doped cobalt–copper sulfide nanostructures for efficient full water splitting

The development of efficient catalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is of great significance for the practical application of water splitting in alkaline electrolytes. Transition metal sulfide electrocatalysts have been widely recognized as efficient catalysts for water splitting in alkaline media. In this work, an original and efficient synthesis strategy is proposed for the fabrication of asymmetric anode (N–(Co–Cu)S_x) and cathode (N–CoS/Cu₂S). Impressively, these electrodes exhibit superior performance, benefiting from the construction of three-dimensional (3D) structures and the electronic structure adjustment caused by N-doping with increased active sites, improved mass/charge transport and enhanced evolution and release of gas bubbles. Hence, N–(Co–Cu)S_x anode exhibits excellent OER performance with only 217 mV overpotential at 10 mA·cm⁻², while N-CoS/Cu₂S cathode possesses excellent HER performance with only 67 mV overpotential at 10 mA·cm⁻². N-(Co–Cu)S_x||N-CoS/Cu₂S electrolyzer presents a low cell voltage of 1.53 V at 10 mA·cm⁻² toward overall water splitting, which is superior to most recently reported transition metal sulfide-based catalysts.

Graphical abstract