Heteroatom functionalized double-layer carbon nanocages as highly efficient oxygen electrocatalyst for Zn-Air batteries

The nonprecious electrocatalyst with high electrocatalytic activity and low cost is urgently desired to fulfill the demands of efficient rechargeable Zn-air batteries (ZABs). Herein, the heteroatom functional carbon-based nanocage Zn-NC is prepared through pyrolysis of ZIF-8. In this process, the organic ligands are converted into partially graphitized carbon with simultaneously reduction of Zn2+ to metal Zn, thus the nitrogen doping porous structure and homogeneous distributed zinc endow the Zn-NC more exposed active surface. Further co-heat treatment of carbonized ZIF-8 precursor with dicyandiamide and glucose results in the formation of Zn, N atomic-level modified carbon material Zn-NC/GD. The dual-shell carbon nanocage structure produces obvious interface properties, which can well bind the escaping metallic zinc to form Zn–N–C bond structure. Benefiting from double carbon modification, interfacial properties, and bonding structure, the Zn-NC/GD performs outstanding half-wave potential (0.86 V) and a lower Tafel slope (97.8 mV dec−1). Consequently, as an air electrode, the Zn-NC/GD also exhibits high open circuit voltage (1.531 V), remarkable power density (326.1 mW cm−2), and excellent specific capacity (824.7 mAh gzn−1). The critical findings demonstrate promising potential to obtain an efficient atomic-level modification of carbon-based electrocatalyst for ZABs. The atomic-level modification of double-layer carbon structure is prepared. The synergetic effect of core and shell not only promotes high conductivity but also exposes abundant active sites, promoting electron transport and facilitating the diffusion of oxygen to the catalytic sites. The assembled ZABs demonstrate a record-high peak power density of 326.1 mW cm−2 and specific capacity of 824.7 mAh gzn−1. [Display omitted] •The double-layer carbon can well bind the escaping zinc metal to induce many defects.•The formation of Zn-Nx bonding structure is beneficial to improve the cycle stability of the electrode.•The assembled Zn-air battery exhibits high open circuit voltage of 1.531 V, superior power density of 326.1 mW cm−2.