Nanocrystal Engineering of Sputter-Grown CuO Photocathode for Visible-Light-Driven Electrochemical Water Splitting

Cupric oxide (CuO) thin film was sputtered onto fluorine-doped tin oxide (FTO) coated glass substrate and incorporated into a photoelectrochemical (PEC) cell as a photocathode. Through in situ nanocrystal engineering, sputtered CuO film shows an improvement in its stability and photocurrent generation capability. For the same CuO film thickness (150 nm), films deposited at a sputtering power of 300 W exhibit a photocurrent of ∼0.92 mAcm(-2) (0 V vs RHE), which is significantly higher than those deposited at 30 W (∼0.58 mAcm(-2)). By increasing the film thickness to 500 nm, the photocurrent is further enhanced to 2.5 mAcm(-2), which represents a photocurrent conversion efficiency of 3.1%. Systematic characterization using Raman, XRD, and HR-TEM reveals that the high sputtering power results in an improvement in CuO film crystallinity, which enhances its charge transport property and, hence, its photocurrent generation capabilities.