Edge-assisted heteroatom doping strategy to break the charge symmetry of single-atom Ni sites for enhanced CO2 electroreduction

Modifying the chemical surrounding of N-doped carbon supported single-atom catalysts (SA/NCs) through heteroatom doping is a mainstream approach to optimize their performance for electrocatalytic CO2 reduction reaction. However, conventional SA/NCs mainly consists of in-plane metal sites feature with tightly symmetrical M–N4 coordination environments, limiting the regulatory strength of heteroatom doping. Herein, we proposed an edge-assisted heteroatom doping regulation strategy by constructing edge-type Ni sites supported on a hollow and leaf-shaped P-doped NC substrate (eNi/H-NPC). The two-dimensional leaf-shaped and hollow carbon can expose enriched edges. The edge structure can promote the accessibility of active sites, more importantly, intensifies electronic perturbation induced by heteroatom doping. Resultantly, the charge symmetry distribution of Ni–N4 site is significantly disrupted, and energy barrier associated with the formation of *COOH intermediate is further diminished. eNi/H-NPC achieves CO faradaic efficiency (FECO) near 100 % at −0.6 V versus reversible hydrogen electrode (vs. RHE) and maintains FECO over 90 % from −0.6 to −1.1 V (vs. RHE) in H-type cells. Remarkably, in gas-diffusion flow cells, eNi/H-NPC exhibits FECO reaches 98.9 % and 96.5 % in neutral and acidic electrolytes with the CO current density reach 283.5, and 397.2 mA cm−2, respectively, which are much superior than that of the bulk material with dominant in-plane active sites. Moreover, eNi/H-NPC serves as an efficient cathode in Zn–CO2 batteries, realized a discharge power density of 4.1 mW cm−2, and exceptional cycling durability over 35 h.