Cu₂O Nanowire Photocathodes for Efficient and Durable Solar Water Splitting

TLDR

Cu₂O is a scalable, nontoxic metal oxide that has attracted attention for solar energy conversion, yet planar devices fall short of the theoretical 14.5 mA cm⁻² due to mismatched light absorption and carrier diffusion, and although nanowire architectures promise improvement, they have rarely yielded higher efficiencies. The authors aim to develop a new synthetic route for Cu₂O nanowire arrays on fluorine‑doped tin oxide and introduce a blocking layer strategy to achieve high‑performance photoelectrodes. They grow well‑controlled‑phase Cu₂O nanowire arrays on FTO using the novel synthesis, then apply a blocking layer to optimize electronic and photonic properties. The resulting Cu₂O nanowire array photocathodes deliver 10 mA cm⁻² photocurrent for solar water splitting and operate stably for over 50 h, setting a new benchmark for metal‑oxide photoelectrodes.

Abstract

Due to its abundance, scalability, and nontoxicity, Cu2O has attracted extensive attention toward solar energy conversion, and it is the best performing metal oxide material. Until now, the high efficiency devices are all planar in structure, and their photocurrent densities still fall well below the theoretical value of 14.5 mA cm–2 due to the incompatible light absorption and charge carrier diffusion lengths. Nanowire structures have been considered as a rational and promising approach to solve this issue, but due to various challenges, performance improvements through the use of nanowires have rarely been achieved. In this work, we develop a new synthetic method to grow Cu2O nanowire arrays on conductive fluorine-doped tin oxide substrates with well-controlled phase and excellent electronic and photonic properties. Also, we introduce an innovative blocking layer strategy to enable high performance. Further, through material engineering by combining a conformal nanoscale p–n junction, durable protective overlayer, and uniform catalyst decoration, we have successfully fabricated Cu2O nanowire array photocathodes for hydrogen generation from solar water splitting delivering unprecedentedly high photocurrent densities of 10 mA cm–2 and stable operation beyond 50 h, establishing a new benchmark for metal oxide based photoelectrodes.