Photoinduced CO2 and N2 reductions on plasmonically enabled gallium oxide

Abstract

Ag-containing ZnO/ β-Ga₂O₃ semiconductor, which exhibit reduced bandgap, increased light absorption, and hydrophilicity, have been found to be useful for photocatalytic CO₂ reduction and N₂ fixation by water. The charge-separation is facilitated by the new interfaces and inherent vacancies. The Ag@GaZn demonstrated the highest photocurrent response, about 20- and 2.27-folds that of the Ga and GaZn samples, respectively. CO, CH₄, and H₂ formed as products for photo-reduction of CO₂. Ag@GaZn catalyst exhibited the highest AQY of 0.121 % at 400 nm (31.2 W/m²). Also, Ag@GaZn generated 740 μmolg^-1 of NH₄⁺ ions, which was about 18-folds higher than Ga sample. In situ DRIFTS for isotopic-labelled ¹³CO₂ and ¹⁵N₂ reaffirmed the photo-activity of as-synthesized catalysts. Density functional theory provided insight into the relative affinity of different planes of heterostructures towards H₂O, CO₂ and N₂ molecules. The structure-photoactivity rationale behind the intriguing Ag@GaZn sample offers a fundamental insight into the role of plasmonic Ag and design principle of heterostructure with improved photoactivity and stability.

Keywords: CO(2) reduction; DRIFTS, density functional theory; Hydrophilicity; Photocurrent response.