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

•Biomass monomers (glucose and fructose) are used as carbon precursors.•Molecular configuration transformation of hexose adjusts microstructure of carbon.•Higher activation barrier of glucose favors the formation of micropore structures.•Glucose-derived carbon exhibits superior activity of ORR compared with fructose.•Glucose-derived carbon as cathode displays higher power density (467.8 mW cm−2).