Efficient ORR catalyst: porous activated carbon prepared from water hyacinth with high N content.

Oxygen reduction reaction (ORR) is an important reaction process that occurs at the cathode of zinc-air batteries. An efficient reaction process is conducive to further research on sustainable energy devices. In order to improve the reaction speed, the ORR electrocatalyst containing uniform Fe–N-C sites in a porous carbon network similar to the shape of moth-eaten rotten wood was prepared using water hyacinth with a thin-layer structure inside as a template. Water hyacinth, plays a variety of synthetic functions in the construction of nanocatalysts, not only has a good enrichment effect on metal elements, but also is rich in N element. The doped Fe elements combine with the carbon and N elements of water hyacinth to form Fe–N-C active sites. The half-wave potential of SHL-Fe-HMNC is raised to 0.881 V (0.838 V for commercial 20wt% Pt/C) compared to the reversible hydrogen electrode (RHE). The power density of the liquid battery prepared based on SHL-Fe-HMNC reaches 110 mW·cm⁻² (90 mW·cm⁻² for 20 wt% Pt/C). Furthermore, the cycle time of ZABs exceeds 200 h. The flexible battery based on SHL-Fe-HMNC has a cycle stability of more than 10 h at a current of 10 mA·cm⁻², and the open circuit voltage (OCV) reaches 1.511 V. [ABSTRACT FROM AUTHOR]