In situ DRIFTS examining the impact of indium doping on activity of CuIn/ZrO₂ catalyst for CO₂ hydrogenation to methanol

We describe the synthesis of CuIn/ZrO2 catalysts via a facile mechanochemical synthesis method. In doping was demonstrated to promote the formation of strong Cu-In2O3 interactions and increase the number of Cu+ sites. The CuIn0.05/ZrO2 catalyst shows relatively high selectivity and space-time yield of methanol (similar to 50% and similar to 1.25 g(CH3OH)gCu(-1)h(-1), respectively) at 300 degrees C and 5 MPa, outperforming those of the Cu/ZrO2 catalyst (similar to 25% and similar to 1.12 g(CH3)g(OH)gCu(-1)h(-1), respectively). Time-resolved in situ DRIFTS results acquired under various reaction conditions (typically H-2/D-2 isotope exchange) demonstrate that the surface Cu+-bound formate was the most reactive intermediate and the subsequent hydrogenation process should be the rate-limiting step, which was positively promoted by the inclusion of In. The strong Cu-In2O3 interaction promotes a decrease in Cu-0 sites, leading to a weak interaction of the Cu-0-bound CO intermediates, thus facilitating further hydrogenation of these species rather than releasing CO product.