Anode-less Hybrid Na–CO Battery with Sodium Harvesting from Seawater for Both Electricity Storage and Various Chemical Production

Abstract

Metal–CO2 batteries have received significant attention. Specifically, Zn–CO2 batteries have attracted interest because of their ability to produce value-added chemicals from CO2. However, owing to the low driving force of Zn (high redox potential, EZn(OH)42–/Zn of −1.2 V vs SHE), they exhibit low energy density and face challenges in the production of high-value C2 chemicals requiring high energy barriers. In this study, we designed hybrid Na–CO2 batteries which utilize the high driving force of Na (low redox potential, ENa+/Na of −2.7 V vs SHE) to achieve high energy density and produce C2 chemicals. This system produced CO, formate, and C2 chemicals with 97.0%, 70.4%, and 37.6% Faradaic efficiency (FE), generating a high power density (25.0 mW cm–2). Furthermore, we constructed an anode-less hybrid Na–CO2 battery that harvests unlimited Na ions from seawater instead of difficult-to-handle Na metal anode, producing CO with an 85.0% FE. This study shows the potential of next-generation sustainable batteries that can address greenhouse gas problems.