Pseudo‐Zero‐Gap Flow‐Type Aqueous Zn‐CO2 Batteries

In pseudo-zero-gap aqueous Zn-CO₂ batteries (AZCBs), the distance between the anode and cathode is minimized, resulting in facilitated OH⁻ ion transport and CO₂ diffusion. Together with eCO₂RR electrocatalysts that could generate formate efficiently and selectively, a record current density of 117.5 mA cm⁻² and power density of 67.0 mA cm⁻² for AZCBs are achieved.

ABSTRACT

Aqueous Zn-CO₂ batteries (AZCBs) generate electricity and convert CO₂ into valuable products simultaneously, while their development is limited due to poor mass transport, low reactivity, etc. Therefore, we develop AZCBs featuring flowing CO₂ gases and electrolytes, gas-diffusion cathodes, and especially a pseudo-zero interelectrode distance. By employing carbon-coated bismuth oxides (Bi₂O₃/C) as the cathode in a pseudo-zero-gap AZCB, a record-high peak power density of 67.0 mW cm⁻² @current density of 117.5 mA cm⁻² is achieved, together with excellent cycling performance over 600 cycles. Specifically, the near-zero distance greatly promotes hydroxide ion transport and CO₂ diffusion by establishing an enhanced concentration gradient at the reaction interface of CO₂ electroreduction. Theoretical simulations further indicate preferred formate production is due to the lower energy barrier compared to the CO pathway, because of the favorable ^*O@Bi adsorption via the ^*OCHO intermediate. Significantly, the developed AZCBs operate efficiently and stably in a simulated Martian atmosphere, which is promising for future Human exploration of Mars, providing a potential solution for simultaneous energy generation and feedstock production in the challenging environment.