A small change in the local atomic environment for a big improvement in single-atom catalysis

How the local atomic environment that relates to the coordination ligand, crystalline structure, and substrate composition influences the catalytic performance of a single-atom catalyst (SAC) has not been fully explored. Here, we theoretically design Ru SAs supported on composition-adjustable inert Cu oxide substrates and investigate their electrocatalytic performance in comparison with that of well-studied bulk Ru and Ru SAs coordinated by nitrogen. Density functional theory (DFT) calculations reveal that Ru SAs supported on Cu oxides (SAs/CuxOy) cause a significant up-shift of the d-band center of Ru SAs in the order of Ru/Cu2O(111) > Ru/Cu(111) > Ru/CuO(111) > Ru-N > Ru(0001), highlighting the superiority of the weak SA-substrate interaction originating from the appropriate coordination environment. Using the nitrogen reduction reaction (NRR) as a probe, the DFT results show that the change of SA electronics due to the use of the CuxOy substrate leads to facile N-2 adsorption which reduces alkaline HER and H* poisoning. Following the theoretical prediction, atomically dispersed Ru on Cu oxides is prepared for the first time and exhibits outstanding catalytic activity and selectivity towards the NRR with an NH3 yield rate of 42.4 mu g mg(cat.)(-1) h(-1) and a faradaic efficiency up to 14.1% at +0.05 V vs. the reversible hydrogen electrode. Finally, we propose new descriptors that help rapidly screen SACs for alkaline NRR. This study represents a successful illustration of the "theoretical design - experimental verification - theoretical generalization" pathway, featuring a slight change in the local SA atomic environment for substantial catalytic performance enhancement.