Co-embedded nitrogen-enriching biomass-derived porous carbon for highly efficient oxygen reduction and flexible zinc-air battery

The configurations of nitrogen species have a crucial influence on the transition metal-nitrogen-doped carbon catalysts (M-N-C). Whereas, how to build more sp2 hybrid N (including pyridinic and graphitic N) to enhance the catalytic activity and charge transfer rate of the carbon-based ORR catalysts remains a challenge. Herein, Co-embedded nitrogen-enriching platanus bark-derived porous carbon (PBPC) material (Co-N-C) was developed from the pyrolytic platanus bark, assisted by impregnating cobalt salt and ethylenediamine nitriding strategy. The synthesized catalyst exhibits a high nitrogen content of 5.02%, of which over 2/3 are high conductivity sp2 hybrid N (consist of pyridinic and graphite-N), suggesting the unity of high activity and conductivity. Thus, it delivers a competitive half wave potential and a lower Tafel slope (69.55 mV dec−1) than Pt-C-20% catalyst. The ZAB with Co-N-C-900 catalyst exhibits a higher open-circuit potential and a peak power density up to 3.5 times (186.17 mW cm−2) higher than that of the Pt-C-20%. During the durability test for 100 cycles (16.7 h), the voltage gap only increased by 4.2%, nevertheless, the Pt-C-20%-based ZAB encountered a catastrophic polarization surge in less than 16 h. When assembling a flexible ZAB, it performs excellent flexibility in bending tests, and the voltage gap merely increased by 1.7% after 100 cycles (16.7 h).