Unraveling the Tandem Effect of Nitrogen Configuration Promoting Oxygen Reduction Reaction in Alkaline Seawater

Developing seawater-based high-performance oxygen reduction reaction (ORR) electrocatalysts is meaningful to renewable energy storage and conversion, and the Fe-based derivatives encapsulated by nitrogen (N) doped carbon are the typical representative. Nevertheless, unrevealing the mechanism of N configuration to ORR activity and chlorine resistance is still a great challenge. In this work, a feasible strategy is developed to prepare controllable pyridinic/pyrrolic-N doped carbon-coated Fe-based electrocatalysts (FexN-NC). Drawing support from the H3PO4 blocking based in situ Fourier transform infrared spectroscopy (FTIR) test and density-functional theory (DFT) calculation, the tandem effect of pyridinic-N and pyrrolic-N on ORR is proved. Additionally, the low hydrogen peroxide (H2O2) yield and 4e(-) pathway of FexN-NC demonstrate that N doping effectively reduces the adsorption of Cl-, which is consistent with the low Cl- adsorption energy of DFT. The half-wave potential (E-1/2) of FexN-NC for ORR reaches 0.874 V in alkaline seawater, and ZABs assembled with FexN-NC as the air cathode deliver a remarkable power density (162 mW cm(-2)), along with excellent long-term durability (>400 h).