Atom-by-atom assembly reveals structure-performance control in PdCu catalysts for CO₂ hydrogenation to methanol

The catalytic conversion of CO₂ to methanol using bimetallic materials presents a promising pathway for sustainable chemical production. A major challenge is the lack of atomic-level control over the catalyst structure and composition, which hinders the understanding of each metal's role in activity and selectivity. Here, we present a solvent-free on-surface assembly of PdCu bimetallic particles, directly from atoms, on ZnO with precise control of the order and quantity of metal atoms added. This atomic-defined interface reveals when atoms are added simultaneously, the metal with stronger ZnO binding governs particle size, but when introduced sequentially the first metal determines particle size. The simultaneously deposited PdCu exhibits the highest reported methanol productivity for PdCu-systems, achieving 8.2 mol h^-1 mol_metal ^-1 at 270 °C and 20 bar. In this catalyst, Cu enhances CO₂ adsorption, suppresses Zn incorporation into the PdCu structure and modulates Pd binding strength to reaction intermediates. This enhances methanol selectivity while maintaining high Pd-driven CO₂ conversion.