On the stability enhancement of cuprous oxide water splitting photocathodes by low temperature steam annealing

Given the intermittent nature of solar radiation, the large-scale use of solar energy requires an efficient energy storage solution. So far, the only practical way to store such large amounts of energy is in the form of a chemical energy carrier, i.e., a fuel. Photoelectrochemical (PEC) cells offer the ability to convert solar energy directly into chemical energy in the form of hydrogen. Cuprous oxide (Cu2O) is being investigated for photoelectrochemical solar water splitting since it has a band gap of 2.0 eV with favorable energy band positions for water cleavage; it is abundant and environmentally friendly. A major challenge with Cu2O is its limited chemical stability in aqueous environments. We present a simple and low-cost treatment to create a highly stable photocathode configuration for H2 production, consisting of steam treatment of the multilayer structures. The role of this treatment was investigated and the optimized electrodes have shown photocurrents over −5 mA cm−2 with 90% stability over more than 50 h of light chopping (biased at 0 VRHE in pH 5 electrolyte).