Boosting ORR performance by single atomic divacancy Zn–N₃C–C₈ sites on ultrathin N-doped carbon nanosheets

Abstract

Single-atom catalysts (SACs) show great promise to improve the performance of catalysis because of their spatially isolated single-atom sites with unique electronic properties. Herein, we construct single Zn atoms anchored on ultrathin two-dimensional (2D) N-doped carbon nanosheets (Zn–SAs/UNCNS) as an efficient electrocatalyst for oxygen reduction reaction (ORR). The microenvironment of Zn–SAs/UNCNS with super ORR intrinsic activity was identified as the divacancy Zn–N3C–C8 by both experiments and theoretical simulations. Density functional theory (DFT) calculations reveal that the divacancy Zn–N3C–C8 sites exhibit near-Fermi electronic states distinct from those of graphene-enclosed Zn–N4–C10 and divacancy trans-Zn–N2C2–C8 sites, which greatly facilitate the ORR process. Furthermore, compared with 3D architecture, the single atomic divacancy Zn–N3C–C8 sites anchored on ultrathin 2D carbon nanosheets show more active site exposure and fast electron transport, which collectively boost the ORR performance, showing a high half-wave potential of 0.91 V versus reversible hydrogen electrode [RHE] and a super turnover frequency (4.99 e− site−1 s−1).