Oxygen-vacancy-stabilized CuO/CuFe2O4/rGO S-scheme heterostructure for highly efficient photoreduction of CO2 to methanol

Photoreduction of carbon dioxide into value added fuels such as methanol (CH 3 OH) is a fascinating and bright area of utilizing CO 2 to neutralize the carbon balance in the atmosphere. However, high activation barrier of CO 2 remains a significant challenge for efficient photoreduction. Introduction of oxygen vacancies (OVs) and band gap tuning are effective approaches to modifying the intrinsic properties of photocatalyst for improved reduction of CO 2 . This study focuses on OVs rich heterostructures of the binary (CuFe 2 O 4 /rGO) and ternary (CuO/ CuFe 2 O 4 /rGO) catalysts were synthesized via co-precipitation method and are evaluated for photocatalytic reduction of CO 2 in methanol under UV-visible illumination. The synergistic effect of abundant OVs and reduced optical band gap in the optimized CuO/ CuFe 2 O 4 /rGO composite facilitated efficient electron-hole (e⁻/h⁺) separation and enhanced charge carrier mobility, resulting in superior photocatalytic performance. However, the optimized 75% CuO/CuFe 2 O 4 /rGO remarkably increased methanol production rate in optimized composite to 3110.98 µmolg -1 cat h -1 , which is 1.53 folds superior to previously reported CuO/rGO photocatalyst. X-ray photoelectron spectroscopy (XPS) and electrochemical impedance (EIS) measurements confirm the interfacial transfer of photo generated electrons from CuFe 2 O 4 to CuO via rGO in TC caused an improvement in reduction efficiency of CO 2 to CH 3 OH. The apparent quantum yield (AQY) of the composite further demonstrates suppression of charge carrier recombination through spatially separated reduction and oxidation sites. This work provides an insight on the design of conceptual S-scheme heterostructure incorporating non-precious metal for ameliorated CO 2 photoreduction performance.