Creation of Mo active sites on indium oxide microrods for photocatalytic amino acid production

As an n-type semiconductor, In2O3 is considered a promising photocatalyst for producing amino acids using biomass derivatives as precursors. However, similar to other intrinsic semiconductors, In2O3 suffers from poor charge dynamics. Herein, we show the synthesis of Mo-doped In2O3 (Mo-In2O3) with a porous rod-shaped structure through a one-step solvothermal reaction followed by calcination. Under visible-light irradiation, Mo-In2O3 achieves a high conversion rate of 81% for the reaction that transforms lactic acid into alanine with a selectivity of 91%. Spectroscopic techniques and density functional theory calculations reveal that Mo doping introduces defect states slightly below the conduction band of In2O3, which improves the separation of photogenerated electron-hole pairs. In addition, Mo atoms on the surface form extra adsorption and reaction centers that greatly enhance the reaction rate. This work provides insights into the development of transition metal-doped semiconductor photocatalysts to produce amino acids.