Why ZnO is the Support for Cu in Methanol Synthesis? A Systematic Study of the Strong Metal Support Interactions

The choice of Cu/ZnO/Al₂O₃ as the industrial catalyst for methanol synthesis is attributed to the strong metal support interactions (SMSI), whereby ZnO is reduced to partially cover the Cu surface, eventually allowing for a favorable synergy between Cu and the Zn species toward higher activity for methanol synthesis. Here, we apply density functional theory (DFT) calculations on a simple atomistic model for the SMSI on Cu(211), screening several oxides as potential supports/promoters. We discover that only ZnO - and, to a lesser extent, Ga₂O₃ - are reducible to cover the Cu(211) surface only partially, allowing for the modification of the Cu surface with Zn or Ga atoms, without diluting the Cu sites necessary for reactants' activation. Other oxides are either too stable to be reduced under reaction conditions, or are too readily reducible into complete wetting of the Cu(211) surface. This work gives fundamental, rational insight into a catalysis that is well-established both in scholarly literature and in industrial practice.