Monosaccharide oxidation powered hybrid zinc-air battery with ultrahigh energy efficiency

Abstract

Rechargeable zinc-air batteries (ZABs) are promising for sustainable energy storage yet remain constrained by the high charging voltages and low energy efficiencies (∼60 %). Herein, we report a hybrid ZAB system (h-ZAB) that replaces the energy-intensive oxygen evolution reaction (OER) with the monosaccharide oxidation reaction (MOR) during charging, enabled by a high-performance nitrogen-doped carbon nanotube (NCNT)-encapsulated NiCo alloy bifunctional catalyst. This catalyst exhibits remarkable bifunctional performance, achieving a MOR potential of 1.29 V (vs. RHE) at 100 mA cm−2 and an oxygen reduction reaction (ORR) half-wave potential of 0.85 V (vs. RHE). Combined experimental and theoretical studies reveal that the built-in electric field at the interface of NiCo and NCNT induces charge redistribution, which optimizes intermediates adsorption and reduces reaction energy barriers, thereby boosting electrocatalytic kinetics. The h-ZAB delivers a low charge-discharge voltage gap of 0.32 V with 82.6 % round-trip efficiency at 10 mA cm−2, simultaneously producing value-added formate. Notably, the system maintains stable operation for 200 h at 40 mA cm−2 with a voltage gap below 0.58 V. This work provides a sustainable strategy integrating energy storage with biomass valorization, offering new insights into renewable energy-electrochemical systems.