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

Abstract

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/Cu_xO_y) 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 Cu_xO_y substrate leads to facile N₂ 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 μg 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.