On the activity of supported Au catalysts in the liquid phase hydrogenation of CO2 to formates

•Au/Al2O3 shows excellent activity in CO2 hydrogenation to formates.•Synergy between Au0 particles and oxide support is crucial for CO2 hydrogenation.•Polar solvents are needed for high catalytic performance.•Surface formate species are key intermediates in the catalytic reaction.•Reaction mechanism over Au/Al2O3 resembles that of the homogeneous counterparts.

The performance of a range of nanoparticulate gold catalysts in the hydrogenation of carbon dioxide to formates was investigated and a superior performance of Au/Al2O3 was revealed. The comparative studies with unsupported gold nanoparticles pointed to the crucial role of the metal-support interaction for the CO2 hydrogenation activity. Cyanide leaching tests complemented by XPS and STEM studies point to the importance of metallic Au0 species for the catalytic activity. The Au/Al2O3 catalyst shows stable activity that allows reaching equilibrium formate yields in a broad temperature range. A kinetic study revealed that a near-zero apparent activation barrier for the hydrogenation reaction is an intrinsic property of the catalytic system. The reaction mechanism is proposed on the basis of the obtained reactivity and characterization data.

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