Boosting charge separation on epitaxial In2O3 octahedron-nanowire crystal facet-based homojunctions for robust photoelectrochemical water splitting

Hindering the recombination of photogenerated charges in photoelectrodes is extremely essential yet hugely challenging. Herein, the In2O3 homojunctions comprising of square nanowires exclusively enclosed by {001} facets and octahedrons fully surrounded by {111} facets are exemplified to illustrate a new strategy of crystal facet-induced charges separation. Kelvin probe force microscopy, spatially resolved surface photovoltage, photo-depositions and theoretical calculations corroborate that the oriented built-in electric field from {111} to {001} facets caused by work function difference of two facets render the photogenerated electrons and holes to accumulate on surface of octahedrons and nanowires, respectively, achieving the effective charges separation with long spatial distance. Benefiting from this advantage, the In2O3 crystal facet-based homojunctions exhibit dramatically higher photoelectrochemical water splitting activity compared with standalone nanowires, octahedrons and truncated octahedrons. The new strategy of boosting the charges separation can be extended to other applications such as photodetectors, solar cells and photocatalysis.