12.04.22 – The in situ electro-conversion of an electrodeposited CuSCN film into Cu₂O is reported to produce photocathodes with improved performance for solar hydrogen production.

Cuprous oxide, Cu₂O, is an inexpensive semiconductor material currently under investigation for the direct conversion of sunlight into hydrogen, however preparing semitransparent and highly active films of Cu₂O has been an ongoing challenge. In a new report from Caretti et al., the LIMNO lab in collaboration with LPI report a new route to construct thin homogeneous Cu₂O layers on transparent fluorine doped tin oxide (FTO) substrates via the in-situ electro-conversion of CuSCN to Cu₂O. We highlight the morphology control of the resulting converted Cu₂O thin-films while demonstrating that they maintain promising performance for solar-driven hydrogen production with a maximum incident photon to current efficiency (IPCE) reaching 60% (at 0 V vs RHE and 450 nm) for a 180 nm-thick film and integrated solar photocurrents up to 4 mA cm–2. In addition, altering the deposition conditions (e.g., applied potential, electrolyte compositions and pH) gives important insight into the mechanism and operation of the electro-conversion process. Overall, we conclude that the converted Cu₂O films are better suited for the coating of high surface transparent scaffolds or as top cells in tandem devices for overall water splitting. Thus, the Cu₂O deposition by electro-conversion is a promising alternative to coat homogenous and thin Cu₂O layer without scattering losses and without compromising the transparency of the electrode.