Cu₂S nanorod arrays with coarse surfaces to enhance the electrochemically active surface area for water oxidation

Water oxidation reaction often impedes the overall water splitting for the multi-step electron transfer process. Transition metal sulfides are earth abundant and widely studied for accelerating water splitting reactions. Cuprous sulfide, which is a common mineral and generally regarded as less active for oxygen evolution reaction, can also effectively promote water oxidation by introducing coarse surfaces on the as-prepared Cu₂S nanorod arrays, with a largely increased double layer capacitance and thereby a greatly improved electrochemically active surface area, which only needs an overpotential of 360 mV to deliver 50 mA cm^-2 and exhibits a rapid kinetics for oxygen evolution reaction. The fabrication strategy of creating coarse surfaces on pre-synthesized nanostructures for increased electrochemically active surface area can be promising for developing precious-metal-free electrocatalysts by providing more active sites and surface areas for water oxidation, and is also valuable for promoting the activity of less active but earth-abundant materials to achieve a better cost-effectiveness in scale-up application of water splitting technology.