Mechanism and catalytic activity of the water–gas shift reaction on a single-atom alloy Al1/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.