Selectively triggering photoelectromacro for CO 2 to CH 4 reduction over SrTiO 3 {110} facet with dual-metal sites.

In this article, the roles of surface-active sites in dominating photoelectron selectivity for CO ₂ reduction products are well demonstrated over photocatalyst models of SrTiO ₃ {100} and {110} facets. On the easily exposed {100} facets terminated with Sr-O atoms, photoelectrons are of 8 mol % for CH ₄ and 92 mol % for CO generation. The Sr-O-Ti configuration in the {110} facets could enrich the surface charge density due to the lower interface resistance for higher photocatalytic efficiency (1.6 fold). The dual sites of Ti and adjacent Sr atoms are active for strong adsorption and activation of the generated CO* species from primary CO ₂ reduction on the surface, thus kinetically favoring the activity of photoelectrons (73 mol %) in hydrogenation for CH ₂ * species and hence CH ₄ product. Inversely, the poor CH ₄ selectivity is due to difficulty in the subsequent photoelectron reduction reaction by the weak adsorption of CO* at the single-Sr site on the {100} facets, independent of the electron and proton concentration. Our results may offer some illuminating insights into the design of a highly efficient photocatalyst for selective CO ₂ reduction.
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