Boosted Inner Surface Charge Transfer in Perovskite Nanodots@Mesoporous Titania Frameworks for Efficient and Selective Photocatalytic CO 2 Reduction to Methane

with selectivities of 88.7 % and 84.2 %, were achieved, respectively, which are better than most reported halide perovskite photocatalysts. Focused ion-beam sliced-imaging techniques were used to directly image the hyperdispersed perovskite nanodots confined in mesopores with tunable sizes ranging from 3.8 to 9.9 nm. In situ X-ray photoelectronic spectroscopy and Kelvin probe force microscopy showed that the built-in electric field between the perovskite nanodots and mesoporous titania channels efficiently promoted photo-induced charge transfer. Density functional theory calculations indicate that the high methane selectivity was attributed to the Bi-adsorption-mediated hydrogenation of *CO to *HCO that dominates CO desorption.