Effects of alcohols as sacrificial reagents on a copper-doped sodium dititanate nanosheets/graphene oxide photocatalyst in CO2 photoreduction

Abstract

Carbon dioxide (CO₂) photoreduction is an intriguing approach that converts CO₂ into high-value substances with the assistance of a photocatalyst. Key to effective photoreduction is to promote the interaction of photo-induced holes and a sacrificial reagent (SCR), separating the holes from photoelectrons and enhancing the rate of the subsequent product generation. Methanol, ethanol, isopropanol, and water SCRs were tested for their ability to assist a copper-doped sodium dititanate nanosheets/graphene oxide heterostructure (CTGN) in CO₂ photoreduction. The CTGN photocatalyst was suspended in a CO₂-saturated aqueous solution with the assigned SCR while illuminated by a mercury lamp. Product samples from the gas and liquid phases were analyzed for targeted product compositions. Methanol SCR exhibited the best performance in facilitating CO₂ photoreduction, producing ethanol as the main product at a total carbon consumption (TCC) of 6544 μmol g_cat⁻¹. The remarkable performance of methanol is attributed to the high diffusivity and excellent stability of the hydroxymethyl radical that developed during the photoreduction. The kinetics studies revealed the first and second order for the CO₂ depletion and product generation rates, respectively, for the alcohol SCRs.