Spatial separation of photogenerated charges on the anisotropic facets of cuprous oxide

Anisotropic facet engineering is an intriguing way to regulate the charge-separation behavior on a semiconductor photocatalyst. Here we show the morphology tailoring of cuprous oxide (Cu2O) from cubic to octahedral and truncated octahedral crystals, and apply Kelvin probe force microscopy to image the photogenerated charge separation on exposed anisotropic facets. The facet junction was observed to greatly improve charge separation efficiency, wherein the photo-induced electrons and holes tend to accumulate on the {100} and {111} facets, respectively. We further correlate the facet-dependent photocorrosion of Cu2O in a photoelectrochemical process with the self-reduction from photo-induced electrons. Our results illuminate the crucial role of anisotropic facet engineering in the regulation of photogenerated charge behaviors and surface reactions in photocatalytic energy conversion.