Boosted Sacrificial-Agent-Free Selective Photoreduction of CO2 to CH3OH by Rhenium Atomically Dispersed on Indium Oxide

Abstract

Solar-energy-driven photoreduction of CO₂ is promising in alleviating environment burden, but suffers from low efficiency and over-reliance on sacrificial agents. Herein, rhenium (Re) is atomically dispersed in In₂O₃ to fabricate a 2Re-In₂O₃ photocatalyst. In sacrificial-agent-free photoreduction of CO₂ with H₂O, 2Re-In₂O₃ shows a long-term stable efficiency which is enhanced by 3.5 times than that of pure In₂O₃ and is also higher than those on Au-In₂O₃, Ag-In₂O₃, Cu-In₂O₃, Ir-In₂O₃, Ru-In₂O₃, Rh-In₂O₃ and Pt-In₂O₃ photocatalysts. Moreover, carbon-based product of the photoreduction overturns from CO on pure In₂O₃ to CH₃OH on 2Re-In₂O₃. Re promotes charge separation, H₂O dissociation and CO₂ activation, thus enhancing photoreduction efficiency of CO₂ on 2Re-In₂O₃. During the photoreduction, CO is a key intermediate. CO prefers to desorption rather than hydrogenation on pure In₂O₃, as CO binds to pure In₂O₃ very weakly. Re strengthens the interaction of CO with 2Re-In₂O₃ by 5.0 times, thus limiting CO desorption but enhancing CO hydrogenation to CH₃OH. This could be the origin for photoreduction product overturn from CO on pure In₂O₃ to CH₃OH on 2Re-In₂O₃. The present work opens a new way to boost sacrificial-agent-free photoreduction of CO₂.

Keywords: CO2; Indium Oxide; Metal-Support Interaction; Methanol; Photocatalysis.