Nanopixelated Cuprous Oxide Photocathodes for Durable Photoelectrochemical Water Splitting

Cuprous oxide (Cu2O) has attracted extensive attention for use in the production of hydrogen through photoelectrochemical water-splitting reactions. However, because the Cu2O photocathode undergoes serious photocorrosion in aqueous environments, it needs a TiO2 protection layer to prevent direct contact with the electrolyte. Although TiO2 is deposited by atomic layer deposition, it is difficult to form a flawless film because of the presence of microscopic particles or ligands of precursors. Herein, we introduce defect-tolerant nanopixelated Cu2O thin film photocathodes to ensure the stability of the photocathodes. Structures comprising discrete pixels restrict defect propagation by corrosion. The pixel size of the pixelated photoelectrodes is theoretically investigated to mitigate the defect density of a protective layer. Nanopixelated Cu2O photocathodes with a pixel diameter of about 400 nm were electrodeposited on a patterned substrate using nanosphere lithography and show 70% stability for approximately 5 h, which is 10 times longer than that shown by a planar cell.