Solution-Processed Cu₂S Photocathodes for Photoelectrochemical Water Splitting

Cu2S has been regarded as a promising solar energy conversion material because of its favorable visible light absorption and earth abundance. Here, we present an indirect preparation method via a solution-processed ion exchange reaction to synthesize stoichiometric Cu2S films with high photoactivity. In addition, we developed a chemical bath deposition method to fabricate CdS buffer layers on Cu2S by adding a reducing agent in the precursor solution, avoiding oxidation of Cu2S. After being coated with the TiO2 protection layer and the RuOx hydrogen evolution catalyst, the Cu2S photoelectrode delivers a photocurrent density of 7.0 mA cm–2 at −0.3 V vs RHE and an onset potential of 0.48 V vs RHE under AM 1.5G simulated sunlight illumination for solar driven water reduction. To our knowledge, this is the first time that Cu2S has been used for solar hydrogen evolution with encouraging performance, which will stimulate further studies on Cu-based photocathodes.