Cu sub(2)O photoelectrodes for solar water splitting: Tuning photoelectrochemical performance by controlled faceting

Cuprous oxide (Cu sub(2)O) films were grown by electrodeposition in aqueous solutions of varying pH. The effect of bath pH on morphology, structural, and photoelectrochemical (PEC) properties of Cu sub(2)O films was investigated. XRD showed that all prepared films were polycrystalline Cu sub(2)O, without formation of competing phases such as CuO and Cu. The film grown in the solution with a pH of 8 is made up of Cu sub(2)O crystallites with preferential (200) planes exposed. The films deposited at solution pH values of 10, 12 and 14 exhibit Cu sub(2)O crystallites with preferential (111) planes exposed. As photoelectrodes these Cu sub(2)O films generate photocurrent upon light illumination. The Cu sub(2)O film grown in the solution with pH of 12 shows the best PEC performance for hydrogen generation. The (111) facets of the Cu sub(2)O film were stable without corrosion during the PEC test. A mechanism for the preferred faceting in alkaline solution has been discussed.