Impact of TiO₂ layer formed on Cu_xS Films on the Photoelectrochemical Water Reduction Process

Solar radiation is the main source of renewable energy capable of satisfying the increasing energy demand without contributing to climate changes using fossil fuels. Energy harvesting from solar radiation requires innovation in materials with appropriate functional properties to produce chemical energy. This study aims to contribute in that sense. It reports the synthesis and characterization of photocathodes for hydrogen evolution based on TiO₂/Cu_xS films formed on FTO glass. Cu_xS is prepared by electrodeposition of copper, followed by chalcogenide formation through immersion in a sulfide source solution and then modified by heat treatment. A TiO₂ layer is deposited on Cu_xS film to favor its stability and charge carrier separation process. The calcination of bare Cu_xS film causes the formation of a mixture of copper oxides. TiO₂ film acts as an effective protector, preserving a larger proportion of Cu chalcogenide species by preventing the complete oxidation, without considerably varying the reducing power of photogenerated electrons in the films. TiO₂ layer favors the absorption of low energy photons and increases the photocurrent, diminishing electron-hole recombination probability.