Constructing thinner micropore-enriched carbon skeleton through molecular configuration transformation of hexose isomers to boost oxygen reduction reaction in Al-air battery

Abstract

Oxygen reduction reaction (ORR) is the core process of metal-air battery. Glucose and fructose are the primary monomers in biomass. In this work, the molecular configuration transformation between pyranose (glucose) and furanose (fructose) is selected as an entry point to construct thinner micropore-riched carbon skeleton with high amount of active sites. The molecular configuration transformation from furanose to pyranose increases the activation barrier associated with the molecular conversion, self-assembly, and aromatization reaction. The higher activation barrier slows the dynamic pyrolysis process, which favors the pore-forming and graphitization of precursors. The Glu-SSC-950–1 (derived from pyranose) exhibits a larger electrochemical active surface area (ECSA) and faster electron transfer, concretely, double-layer capacitance increases from 7.4 to 14.9 mF cm−2. And the Glu-SSC-950–1 exhibits a higher half-wave potential (0.847 V) and kinetic current density at half-wave potential (3.91 mA cm−2) than Fru-SSC-950–1 (derived from furanose, 0.801 V, 2.92 mA cm−2). In practical application, the Al-air battery with Glu-SSC-950–1 exhibits a superior peak power density (467.8 mW cm−2) than Fru-SSC-950–1 (400.7 mW cm−2). In general, we present an approach for the preparation of highly active ORR biomass-derived carbon.