Asymmetric Zinc–Nitrate/Hydrogen Battery Chemistry Coupling Electrochemical Hydrogen Charge and Energy Storage

Abstract

Aqueous zinc–nitrate batteries (ZNBs) have attracted considerable interest because they combine energy storage with nitrate remediation and ammonia production. However, their practical application is hindered by large energy loss during charging, resulting in limited overall energy efficiency. Herein, a rechargeable zinc–nitrate/hydrogen battery (ZNHB) is proposed to couple electrochemical hydrogen utilization with energy storage with asymmetric battery chemistry. During discharge, the ZNHB with a high-entropy catalyst outputs electricity with a peak power density of 15 mW cm–2 and steady ammonia production. While charging, hydrogen is charged into the system and greatly reduces the charging potential to much lower than the discharging potential, simultaneously harvesting electrical energy and hydrogen chemical energy. As a result, the ZNHB achieves an overall energy efficiency of 72.9%, exceeding that of conventional ZNBs. Furthermore, a hydrogen chemical-to-electrical energy efficiency of 62.6% is achieved, demonstrating the effective utilization of hydrogen chemical energy during charging. With this alternate hydrogen-charging and electric outputting design, the rechargeable ZNHB provides a new mode for stationary hydrogen electrochemical charging and electric energy storage.