Reduced TiO2 quantum dots/graphene for solar light driven CO2 reduction into precisely controlled C-1 vs C-2 hydrocarbon products without noble Co-catalyst

Abstract

Photocatalytic CO2 reduction is a logical approach to overcome the energy crisis as well as to curb the anthropogenic CO2 emission by converting atmospheric CO2 with water vapour under irradiation into hydrocarbon fuels. Herein, for the first time, a noble metal-free photocatalyst comprised of reduced TiO2 quantum dots (TQDs) dispersed over graphene sheets has been successfully synthesized and employed for this reaction. EELS investigation reveals the addition of graphene has imparted oxygen vacancies inside TQDs, which in turn helps to enhance broad solar light absorption. TRPL spectroscopy revealed a prolonged charge separation in the heterostructure. Depending on graphene content, the ratio of the products has been changed; CH4:C2H6 from 3.41:1 to 1:1.62. The optimized sample exhibits 2.8- and 3.7-fold increment of CH4 and C2H6 yields compared to TQDs. Under the continuous mode, the photocatalyst has shown excellent stability of 72 h. © 2022 Elsevier B.V.