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

Abstract

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 V_RHE in pH 5 electrolyte).