Efficient CO2 photoreduction triggered by oxygen vacancies in ultrafine Bi5O7Br nanowires

Sluggish charge kinetics, poor photoabsorption and low CO2 affinity have been regarded as the main obstacles inhibiting the efficiency of CO2 photoreduction. Herein, freestanding ultrafine Bi5O7Br nanowires with abundant oxygen vacancies were initially fabricated to synchronously optimize these critical processes. The 1D ultrafine configuration and abundant oxygen vacancies endow the Bi5O7Br nanowires with extended photoadsorption, boosted charge separation and enhanced interfacial CO2 adsorption and activation. Density functional calculations reveal that the presence of oxygen vacancies on the Bi5O7Br surface can not only afford abundant localized electrons and lower the CO2 reaction energy barriers, but also have a stronger covalent interaction and more efficient electron exchange and transfer between CO2 and oxygen vacancies. Without any co-catalyst or sacrifice reagent, OV-rich Bi5O7Br nanowires show a 27.76-fold enhancement of CO2 photoreduction activity relative to bulk Bi5O7Br in the gas-solid system. This work may inspire the future design of ultrafine catalysts for artificial photosynthesis.