Water acting as a catalytic promoter for electron-proton transfer in the Pt single atom catalyzed environmental reduction reactions

Water, which is the host of life, introduces many unusual features into the kinetics and energetics of biological reaction systems catalyzed by enzymes. Single atom catalyst has great potential to mimic biological enzymes in regard to special catalytic sites and high efficiency. Here we report a significant promotion by H2O in the environmental reduction of nitrobenzene on an environmentally friendly humic acid supported Pt single atom catalyst. No nitrobenzene conversion took place when only organic solvents were used while high activity of the catalyst was observed in aqueous mixtures (turnover frequency is as high as 1883 h(-1)). Experiments and density functional theory calculation show that H2O greatly decreased the energy barrier by enabling a biomimetic electron-proton transfer for the hydrogenation process even on single atom Pt catalyst, and a new reaction pathway with phenyl-lambda(1)-azane as intermediate in the direct hydrogenation of nitrobenzene is proposed.