High-rate and selective conversion of CO2 from aqueous solutions to hydrocarbons

Abstract

Electrochemical carbon dioxide (CO2) conversion to hydrocarbon fuels, such as methane (CH4), offers a promising solution for the long-term and large-scale storage of renewable electricity. To enable this technology, CO2-to-CH4 conversion must achieve high selectivity and energy efficiency at high currents. Here, we report an electrochemical conversion system that features proton-bicarbonate-CO2 mass transport management coupled with an in-situ copper (Cu) activation strategy to achieve high CH4 selectivity at high currents. We find that open matrix Cu electrodes sustain sufficient local CO2 concentration by combining both dissolved CO2 and in-situ generated CO2 from the bicarbonate. In-situ Cu activation through alternating current operation renders and maintains the catalyst highly selective towards CH4. The combination of these strategies leads to CH4 Faradaic efficiencies of over 70% in a wide current density range (100 – 750 mA cm-2) that is stable for at least 12 h at a current density of 500 mA cm-2. The system also delivers a CH4 concentration of 23.5% in the gas product stream.

Developing Catalysts Integrated in Gas-Diffusion Electrodes for CO2 Electrolyzers

“…The p-d orbital hybridization of Cu and Ga adjusts the binding strength of *CO facilitating C–C coupling. Dinh et al reported a flow cell fabricated with porous a Cu electrode and a bipolar membrane . The Cu was activated in situ by cycling between positive and negative bias, and the bipolar membrane ensured that bicarbonates were regenerated in situ to CO 2 .…”

Ethylene Production from Carbonate Using a Bipolar Membrane Electrolysis System

“…Bipolar membrane (BPM)-based electrolyzers, however, can desorb and compress CO 2 from an alkaline carbon capture solution through a pH swing process . This in situ production of CO 2 can then undergo CO 2 reduction reaction (CO 2 RR) to form products such as CO, CH 4 , C 2 H 4 , HCOO – , and C 2 H 5 OH. − One critical challenge with this configuration is that excessive production of protons at the BPM junction can create a locally acidic region near the catalyst, promoting the hydrogen evolution reaction (HER) instead of CO 2 RR (lowering the C 1+ or 2+ FE). , Most prior investigations of (bi)­carbonate electrolysis with a BPM focus on the formation of C 1 products (i.e., CO, syngas, and CH 4 ). − The production of pure syngas (mixture of CO and H 2 ) has also been demonstrated within a carbonate-based electrolysis cell. , However, few have demonstrated the production of C 2+ products from bicarbonate or carbonate-based electrolytic cells. ,, Controlling the local pH emerges as a crucial factor as an acidic condition is essential for CO 2 release from (bi)­carbonate, while an alkaline condition is necessary to inhibit HER and promote multicarbon product formation at the catalyst-layer–BPM interface. Additionally, the generation of CO 2 from (bi)­carbonate is highly dependent on various parameters, such as the concentrations of (bi)­carbonates, bulk pH, and applied current densities.…”

Ni‐Based Catalysts for CO2 Methanation: Exploring the Support Role in Structure‐Activity Relationships

“…Over the years an increase emission of CO 2 has been recorded due to the combustion of fossil fuels and industrial processes [1,2] . Therefore, different techniques like photocatalysis, electrocatalysis and thermal catalysis have been developed for the conversion of CO 2 to useful chemical fuels, [3–7] and among them, thermal conversion of CO 2 to methane is a widely used process to obtain natural gas at mild condition [8–11] . However, CO 2 methanation is a thermodynamically favored and kinetically limited reaction, designing an active catalyst is required for this exothermic reaction.…”