Mechanism and catalytic activity of the water–gas shift reaction on a single-atom alloy Al ₁ /Cu (111) surface

The mechanism and activity of the water-gas shift reaction (WGSR) on single-atom alloy Al₁/Cu (111) and Cu (111) surfaces were studied using GGA-PBE-D3. Al₁/Cu (111) exhibited bifunctional active sites, with the Al site being positively charged and the Cu site negatively charged due to electronic interactions. This led to selective adsorption of H₂O and CO. Al₁/Cu (111) promoted H₂O adsorption and dissociation, reducing the energy barrier to 0.67 eV compared with 1.13 eV on the Cu (111) surface. Meanwhile, Cu served as the active site for H₂ formation, which is the rate-determining step, with an energy barrier of 0.95 eV. The Al-O and Cu-C bonds cooperatively increased the interaction strength of O-containing intermediates. Al₁/Cu (111) promoted the whole WGSR through cooperativity, reducing the overall apparent activation energy. This work gives insights for the design of single atom alloy (SAA) catalysts with p-p orbital energy level matching, which facilitates orbital interactions between Al and H₂O, thus achieving excellent WGSR activity.