Microalgae-derived single-atom oxygen reduction catalysts for zinc-air batteries

The need to fight against global warming has motivated the development of new technologies for green production of various chemicals and materials. Microalgae can convert CO2 into valuable biofuels, thus playing important roles in carbon neutrality. However, appropriately utilization of microalgae biomass remains an important issue to address. Here we demonstrate that the microalgae biomass with abundant membrane-bound biomolecules and singly isolated metal atoms can be upgraded into single-atom site catalysts (SACs) with high oxygen reduction reaction (ORR) activity. Through hydrothermal and pyrolysis treatment of microalgae, Fe-N4 structured SACs (malg-SACs) are obtained, as confirmed by near edge X-ray absorption fine structure (NEXAFS), X-ray absorption near-edge structure (XANES), and extended X-ray absorption fine structure (EXAFS). Under optimal conditions, the malg-SAC exhibits a remarkable ORR activity (E1/2 = 0.875 V vs. RHE), outstanding longterm stability, and good resistance to CO and CH3OH poisoning. When assembled in a primary zinc-air battery, the full device reaches a maximum power density of 220.7 mW cm-2 with negligible voltage decay over the 6 h test, far outperforming the commercial Pt/C (112.1 mW cm-2). Our work reports a sustainable pathway to convert CO2-capture biomass into high-performance SACs, simultaneously addressing environmental and energy issues.

Automated summary

The development of new green technologies for chemical and material production is driven by the need to combat global warming. Microalgae can convert CO2 into biofuels, making them important for carbon neutrality. This study demonstrates that microalgae biomass can be upgraded into single-atom site catalysts with high oxygen reduction reaction (ORR) activity. The resulting catalysts show remarkable stability and resistance to poisoning, and outperform commercial catalysts in a zinc-air battery. The research offers a sustainable pathway for converting CO2-capture biomass into high-performance catalysts, addressing environmental and energy concerns simultaneously.