Based on previous work on the CO 2 hydrogenation by thermal and electrochemical catalysis, we choose Cu, Zn, and Pd as host metals in our SAAs. 12 different SAs are combined with each of the three hosts resulting in 36 SAAs. Overall, 120 flat and stepped SAA surfaces and 780 different surface sites were considered (Figure ). The sites in the pristine surfaces of the three host metals were also included in the study.