Cation vacancy activating surface neighboring sites for efficient CO2 photoreduction on Bi4Ti3O12 nanosheets

Abstract

Inefficient charge separation and insufficient surface catalytic sites remain the main impediment in developing highly efficient and selective catalysts for CO₂ photoreduction. Surface defects are effective, but their function is always constrained within the defect location. Herein, a desirable surface cation vacancy strategy is implemented to solve the above obstacles over Bi₄Ti₃O₁₂ nanosheets. The surface Ti vacancy (V_Ti) creates an atomic-level charge transfer channel on the surface of Bi₄Ti₃O₁₂, allowing a rapid transfer of photon-generated electrons from the V_Ti site of neighboring Ti and O atoms to CO₂ molecules. More importantly, V_Ti activates neighboring Ti and O atoms, which allows them a stronger ability for enhancing CO₂ adsorption and conversion. Thus, a convenient and swift charge transfer channel and activated near surface region are formed on the surface of Bi₄Ti₃O₁₂, profoundly boosting the CO₂ reduction process, as evidenced by experimental and theoretical results collectively. Without any sacrificial agents or cocatalysts, Bi₄Ti₃O₁₂ with an optimal V_Ti concentration exhibits an outstanding CO production rate of 15.17 μmol g⁻¹ h⁻¹, nearly 5 times higher than that of pristine Bi₄Ti₃O₁₂. This work unfolds a new function of surface cation vacancies to substantially enhance CO₂ photoreduction.