Overall Photoelectrochemical Water Splitting using Tandem Cell under Simulated Sunlight

A stand‐alone photoelectrochemical (PEC) water‐splitting system driven only by sunlight was demonstrated with a tandem‐scheme of Pt/CdS/CuGa3Se5/(Ag,Cu)GaSe2 photocathode and NiOOH/FeOOH/Mo:BiVO4 photoanode in a neutral phosphate buffer solution as an electrolyte. The as‐prepared semi‐transparent Mo:BiVO4 layer allows sunlight to pass through the top photoanode and reach the bottom photocathode. Consequently, the tandem cell showed stoichiometric hydrogen and oxygen evolution with a solar‐to‐hydrogen (STH) conversion efficiency of 0.67 % over 2 h without degradation. The stability and STH efficiency are the highest among similar configuration of PEC tandem cells. Working together: A tandem photoelectrochemical cell composed of a photoanode (NiOOH/FeOOH/Mo:BiVO4) and photocathode (Pt/CdS/CGS/ACGSe) is reported. The tandem cell utilizes a wide range of the simulated sunlight from the UV to the visible region to yield solar‐to‐hydrogen conversion efficiencies of up to 0.67 %, which is one of the largest values ever reported among cells of similar configuration for overall water splitting.