Single-atom Zn sites decorated with ZnO clusters by in-situ carbon reduction and limited evaporation for boosting oxygen reduction.

The regulation of electron distribution of single-atom catalysts (SACs) by metal oxide groups is an effective strategy for boosting their intrinsic activity of oxygen reduction reaction (ORR). However, it remains a challenge to precisely control synthesis and achieve high activity of the catalyst. Herein, single-atomic Zn sites decorated with ZnO clusters on porous hollow carbon spheres (Zn/ZnO@NC) was constructed by in-situ carbon reduction and limited evaporation strategy. We reported the detailed evolution process of the template in-situ volatilization from ZnO spheres to the coexistence of Zn SAs and ZnO clusters. The influence of ZnO cluster on the reaction velocity at the ZnN sites was investigated by means of density functional theory (DFT) calculation. ZnO clusters changed the charge distribution and decreased the reaction energy barrier. Such catalyst has a half-wave potential (E) of up to 0.90 V for ORR. As the air electrode in Zn-air batteries (ZABs), Zn/ZnO@NC shows an open-circuit voltage (OCV) of the assembled Zn-air battery is 1.61 V. This work not only provides a new idea for designing highly accessible catalysts for practical applications, but also provides a guidance for studying structure-property correlations of Zn electrocatalysis.