Anisotropic Crystal Growth via Defects Cluster Boosted Solar Photoelectrochemical Water Splitting by n-Cu2O Thin Films.

The present study reports on anisotropic growth of the Cu2O crystals deposited on an indium tin oxide coated glass substrate via facile electrodeposition along with low temperature calcination in favor of solar photoelectrochemical water splitting. In particular, X-ray diffractometry, transmission and scanning electron microscopy reveal that appreciable oxygen vacancies are populated in the Cu2O crystals with a highly branched dendritic thin film morphology, which are presumably clustered upon the post thermal treatment to give birth to the catalytically active (111) facets. Such Cu2O thin film shows n-type conduction with a donor concentration on the order of 1017 cm-3 and a flat-band potential of -1.19 V vs. silver/silver chloride (Ag/AgCl) electrode that are derived alternatively from the Mott-Schottky analysis. This in turn renders this material employed as the photoanode and most importantly, that delivers a photocurrent amounted to 2.2 mA⋅cm-2 at a potential of 0.3 V (vs. Ag/AgCl electrode), surpassing those reported in the literature more than twofold. Such superiority originates mostly from the synergism of selective facet growth within the Cu2O crystals that have decent crystallinity reflected otherwise in the Raman and photoluminescence spectroscopy and favorable bandgap of 2.1 eV derived alternatively from the UV-Vis spectroscopy, respectively. Evidently, the n-type Cu2O thin film reported herein holds great promise for solar-related applications.