Tuning the anisotropic facet of SrTiO3 to promote spatial charge separation for enhancing photocatalytic CO2 reduction properties

Abstract

A key issue in artificial photosynthesis is how to improve the separation and transport efficiency of photogenerated carriers. The use of facet effect to promote the spatial charge separation is an effective strategy to improve the photocatalytic performance of photocatalysts. However, high-energy crystal facets with high surface energy are highly susceptible to disappear during the growth process due to the faster growth rate of high-energy facets, making the preparation of multi-facets or high-energy facets is very challenging for SrTiO3 (STO) photocatalysts. In this work, we have obtained 26-facet STO with high-energy {111} facets by molten salt method, which is attributed to the selective adsorption of Cl- on the high-energy facet. By in situ photodeposition experiments, we found that the reduction and oxidation sites were distributed on the anisotropic {100} and {111}/{110} facets of 26-facet STO, respectively. The 26-facet STO with high-energy {111} facets possesses better photocatalytic CO2 reduction properties compared to common 6-facet STO and 18-facet STO. The excellent performance is attributed to the strong internal electric field generated by the difference in the work function between the anisotropic facets, which induces the photogenerated electrons to migrate directionally to the {100} facets and the holes to migrate to the {111} and {110} facets, which dramatically promotes the effective separation of the photogenerated carriers. Moreover, the spatial distribution of the oxidation and reduction reaction sites effectively inhibits the reverse reaction and promotes the slow water oxidation reaction to release more protons, thus improving CO2 reduction performance. This will be an important reference for the design and preparation of efficient photocatalysts for artificial photosynthesis.