High-throughput Design of Single-atom Catalysts with Nonplanar and Triple Pyrrole-N Coordination for Highly Efficient HO Electrosynthesis.

Single-atom catalysts (SACs) with nonplanar configurations possess unique capabilities for tailoring the oxygen reduction reaction (ORR) catalytic performance compared with the ones with planar configurations, owing to the additional orbital rearrangement arising from the asymmetric coordination atoms. However, the systematic investigation of these nonplanar SACs has long been hindered by the difficulty in screening feasible nonplanar configurations and precisely controlling the coordination structures. Herein, we demonstrate a combined high-throughput screening and experimental verification of nonplanar SACs (ppy-MN) with metal atoms triple-coordinated by pyrrole-N, for highly active and selective 2e ORR electrocatalysis. With the additional p-orbital rearrangement of N-ligands for ppy-MN during catalysis, a new descriptor on the energy difference between d-band center of metal sites and p-band centers of N-ligands (Δϵ) is proposed to accurately identify the relationship between their catalytic activities and electronic structures, on top of the conventional d-band center theory. Consequently, ppy-ZnN is identified with excellent 2e ORR activity (η=0.08 eV) and selectivity, as well as a low 2e ORR kinetic barrier under alkaline condition owing to a strong hydrogen bonding between OOH* intermediate and interfacial water, which is then experimentally verified by its high electrocatalytic HO yield (43 mol g h) and selectivity (92 %) under alkaline condition. This study thus presents a proof-of-concept demonstration of the performance-oriented and precise coordination design of nonplanar SACs for efficient HO electrosynthesis, and, more importantly, provides an essential complement to the d-band theory for more accurately predicting the catalytic activities of catalysts with nonplanar configurations for series potential electrochemical processes.