Inherent Facet-Dominant effect for cobalt oxide nanosheets to enhance photocatalytic CO2 reduction

Highly specific exposed to different crystal facets remarkably affect the CO2 reduction photoreactivity. Thereby, we give examples of well-interpretated Co3O4 nanosheets, which dominating with respective facets, {1 1 2} and {1 1 1}, to explore the reactivity of the photocatalysis's special exposed crystal facets in the photocatalytic CO2 reduction. The true photoreactivity of Co3O4-{1 1 2} were testified to be remarkably higher than Co3O4-{1 1 1} for both CO evolution and CH4 production reactions. Further photoelectrochemical detection studies have confirmed that the different reactivity is not only due to the different morphologies of the calcined materials under different temperature conditions, but controlled by the different exposing facets, giving rise to the photogenerated carriers and effective space separation. Under the calcination condition of 673 K, CO and CH4 evolution rates of Co3O4-{1 1 2} reached 96.4 and 18.94 μmol·g−1·h−1. The mechanism of the reaction was further confirmed by in-situ fourier transform infrared spectroscopy and DFT calculation. Effective separation of photogenerated carriers and specific flaky shapes, crystal facets, and surface atomic arrangement all contribute to the high activity of the carefully designed Co3O4 photocatalysis.