Oxygen vacancy mediated bismuth stannate ultra-small nanoparticle towards photocatalytic CO₂-to-CO conversion

Photocatalytic CO₂ reduction suffers from the weakness of high energy barrier, low efficiency and poor selectivity. Exploring effective strategy to enhance the adsorption and activation behavior of CO₂ molecules is an alternative approach to boost CO₂ photoreduction performance. In this work, abundant oxygen vacancies (V_O) are introduced onto Bi₂Sn₂O₇ nanoparticles (NPs) by decreasing their size down to about 4 nm. The V_O mediated NPs exhibit a tremendous 8.1 times enhanced performance than the bulk counterpart towards CO₂-to−CO conversion in pure water. This is attributed to fast charge diffusion and abundant Vo for effective CO₂ adsorption and activation in the ultra-small nanoparticles. The V_O mediated Bi₂Sn₂O₇ NPs have electron back donation nature and optimized electronic structure for effectively activating CO₂, which were demonstrated by density functional theory calculations. During the reduction process, the Vo can effeciently stabilize the COOH* intermediates, and also lower the energy barrier of CO desorption determining step.