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

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.