Microalgae biomass-derived nitrogen-enriching carbon materials as an efficient pH-universal oxygen reduction electrocatalyst for Zn-air battery

Abstract

Abstract Microalgae, with robust nutrition intake capacity and rapid growth rate, could enrich large amounts of nutrition elements (N and P) and CO2 from the environment, providing an effective way to counter water eutrophication and global warming. However, how to effectively dispose the massive biomass rich in carbon and nutrition contents is still a big challenge. In this work, the microalgae biomass was used as a precursor to synthesize the N-enriching porous carbon materials via a facile pyrolysis method. The as-synthesized materials exhibited robust electrocatalytic oxygen reduction reaction (ORR) activities in both alkaline and acidic media, showing a superb catalytic ORR activity (high catalytic activity, favorable durability, as well as excellent tolerance to methanol and CO). Large surface area with mesopore structure, as well as abundant active nitrogen sites were mainly responsible for their robust electrocatalytic performance. The pyridinic N species was identified as the ORR catalytic site, and its contribution was quantitatively analyzed. The performance of the as-assembled Zn-air battery equipped with the as-synthesized N-enriching carbon materials for air cathode catalyst further confirms its superb effectiveness for ORR. The results provided in this work would provide a sustainable and cost-effective method to produce high-performance carbon materials for energy storage and conversion from the large-scale biomass wastes.