In3+-doping and oxygen vacancies co-engineering active sites of Bi2WO6 hollow nanospheres to achieve efficient photoreduction of CO2 to CO with nearly 100 % selectivity

Abstract

Photocatalytic reduction of CO₂ into renewable fuels has been received as one of the most promising technologies to alleviate the problems of greenhouse effect and energy crisis; however, achieving the efficient conversion of CO₂ selectively into a single product remains a significant challenge. In this study, we report that In³⁺-doping and oxygen vacancies co-engineer the active sites of the Bi₂WO₆ (BWO) photocatalyst to achieve efficient photoreduction of CO₂ selectively into CO. Novel In³⁺-doped BWO hollow nanospheres with abundant oxygen vacancies have been hydrothermally prepared by using ethylene glycol (EG) as the solvent. Comprehensive experimental and theoretical studies demonstrate that the In³⁺ doping and oxygen vacancies synergistically lead to the formation of coordination-unsaturated Bi active sites, enhance the CO₂ adsorption on the photocatalyst, promote the electron transfer from the photocatalyst to CO₂, and lower the energy barriers of CO₂ photoreduction; moreover, mixed defect states are introduced within the bandgap, which expand the light absorption range, promote the separation of photocarriers and prolong their lifetime. These factors collectively endow the photocatalyst with excellent CO₂ photoreduction performance. The optimal In_0.075BWO-EG results in the CO yield rate as high as 95.6 μmol g⁻¹h⁻¹ with 99.7 % selectivity, which is superior to that of other reported BWO-based photocatalysts. This research offers an important strategy and understanding for improving the CO₂ photoreduction performance of photocatalysts.