Defective Indium Tin Oxide Forms an Ohmic Back Contact to an n-Type CuO Photoanode to Accelerate Charge-Transfer Kinetics for Enhanced Low-Bias Photoelectrochemical Water Splitting.

In significant contrast to the tremendous research efforts mostly geared to addressing the severe hole accumulation at the back contact of a p-type CuO photocathode with a fluorine-doped tin oxide (FTO) substrate, sluggish electron transfer from an n-type CuO photoanode to a tin-doped indium oxide (ITO) substrate has been largely overlooked. To tackle this issue that has been reported to largely limit the photoelectrochemical performance of n-type CuO photoanodes at a low bias, the present contribution puts forward a strategy to introduce oxygen vacancies into the ITO substrate via an unprecedented yet facile electrochemical approach. Such defect engineering turns out to decrease the work function of the ITO substrate, which in turn approaches the conduction band extremum of n-CuO to highly efficiently extract the photoexcited electrons therein.

Defect-Cluster-Boosted Solar Photoelectrochemical Water Splitting by n-Cu O Thin Films Prepared Through Anisotropic Crystal Growth.

Anisotropic growth of Cu O crystals deposited on an indium-doped tin oxide-coated glass substrate through facile electrodeposition and low-temperature calcination results in favorable solar photoelectrochemical water splitting. XRD, TEM, and SEM reveal that appreciable oxygen vacancies are populated in the Cu O crystals with a highly branched dendritic thin film morphology, which are further substituted by Cu atoms to form Cu antisite defects exclusively along the [111] direction. The post-thermal treatment presumably accelerates such migration of the lattice imperfections, favoring the exposure of the catalytically active (111) facets.