Catalysis of material surface defects: Multiscale modeling of methanol synthesis by CO2 reduction on copper

The effect of the structure of copper catalyst surface on CO2 conversion has been a long-standing research effort, both theoretically and experimentally. In this paper, flat Cu(111) and stepped Cu(533) surfaces are theoretically studied for catalytic CO2 hydrogenation to methanol, an important carbon utilization process for tackling modern environmental pollution problems. First-principles multiscale modeling using density functional theory (DFT) and mesoscopic kinetic Monte Carlo (kMC) is employed to simulate the complex reaction pathway, focusing on the role of surface defects on the overall catalytic selectivity and activity at laboratory operating conditions. The contribution of the electronic (interaction energy) and geometric (distortion energy) effect to the adsorbates binding energy is evaluated and discussed. The results show that a stepped Cu(533) surface enhances the selectivity and activity of the methanol synthesis, with selectivity up to 84% and turn-over frequency (TOF) up to 10(-4) s(-1), which is over 4 orders of magnitude better than a flat Cu(111) surface. It is found that the surface defect, compared to the Cu(111) surface and other Cu/metal oxide alloys, promotes the H2COH hydrogenation pathway, resulting in higher total CH3OH yields. The study provides an insight into surface defects engineering, serving as a step towards the rational design of multifaceted copper catalysts.