Reversible Aqueous Zinc–CO₂ Batteries Based on CO₂–HCOOH Interconversion

Abstract

As a promising technique for CO2 fixation/utilization and energy conversion/storage, the metal–CO2 battery has been studied to improve its interconversion between CO2 and carbonates/oxalates. Herein, we propose and realize a reversible aqueous Zn–CO2 battery based on the reversible conversion between CO2 and liquid HCOOH on a bifunctional Pd cathode. The 3D porous Pd interconnected nanosheet with enriched edge and pore structure, has a highly electrochemical active surface to facilitate simultaneous selective CO2 reduction and HCOOH oxidation at low overpotentials. The resulting battery has a 1 V charge voltage, a cycling durability over 100 cycles, and a high energy efficiency of 81.2 %. The battery mechanism is proposed as Zn+CO2+2 H++2 OH−↔ ZnO+HCOOH+H2O, through which the reversible conversion between CO2 and liquid HCOOH was realized.

Tuning electronic and composition effects in ruthenium-copper alloy nanoparticles anchored on carbon nanofibers for rechargeable Li-CO2 batteries

“…Conversion of carbon dioxide (CO2) to renewable energies in an environmental-friendly way has been considered as an appealing and essential approach for mitigating climate change and achieving sustainable development [1][2][3]. In recent decades, various routes have been investigated and employed to fulfill this purpose [4][5][6][7].…”

A Zn–CO2 Flow Battery Generating Electricity and Methane

“…Thus, despite the CHF electrode not being modified by catalytically active heteroatoms and metal‐containing species, [EMIM] + cations will play as the promoter to initiate CO 2 reduction. Metallic zinc is selected as the anode based on the following considerations: 1) Zn enjoys proper reactivity to drive CO 2 methanation ( E o Zn2+/Zn = −0.762 vs E° CO2/CH4 = 0.17 V); 2) Zn electrode, and even Zn 2+ ions, display unique activity in the enhancement of CO 2 electrochemical reduction; 3) it is easy to revert the oxidized Zn anode to Zn 0 by an electrochemical method, thus making the Zn–CO 2 battery renewable; 4) Zn is an earth‐abundant and inexpensive metal that is capable of sustaining mass production of the battery …”

“…These batteries generally converted CO 2 to solid‐state products such as amorphous carbon and oxalates. Very recently, Wang and co‐workers obtained liquid reduction product of formic acid in a battery adopting porous Pd nanosheets as the cathode …”

“…However, as a technology at very early stage, issues still exist for metal–CO 2 battery technologies: 1) The products are limited to carbon,4a oxalate, and formic acid that require less than 4e − transfer, while high reduction of CO 2 to hydrocarbons has not yet been achieved because the processes involve kinetically challenging proton‐coupled electron transfer (PCET) reactions (≥8H + and 8e − ) . Hydrocarbons should be preferred as reduction products, not only because they are high value‐added fuels or chemicals, but also because the huge global demands on hydrocarbons can lead to a meaningful contribution to the reduction of CO 2 emission .…”

“…3) Coin‐type cells with a perforated cathode shell are commonly employed to encapsulate the electrodes and the resultant batteries need to operate in CO 2 ‐filled airtight containers 4a,5b,6. Electricity can be output from the closed system, while the reduction products have to circulate in the system through reversible battery reactions CO 2 + M ↔ P + M n+ + n e − (M = metal; P = reduction product) 5b,7. Owing to a carbon‐neutral interconversion between CO 2 and reduction products, the battery is hard to impact on global CO 2 levels 10b.…”