Physics

Reversible hydrogen electrode

Electrode

Organic chemistry

Current density

Electrocatalyst

Membrane

Analytical Chemistry (journal)

Engineering

Faraday efficiency

Physical chemistry

Inorganic chemistry

Chemistry

Materials science

Carbonate

Membrane electrode assembly

Reference electrode

Cathode

Quantum mechanics

Electrolyte

Chemical engineering

Chromatography

Electrochemistry

Biochemistry

ACS Energy Letters

The formation of (bi)carbonates is a pressing issue for CO2 electroreduction in neutral or alkaline solutions. It adversely causes low single-pass conversion efficiency as a result of (bi)carbonate crossover, as well as limited device lifetimes as a result of (bi)carbonate precipitation at the cathode. One emerging solution to circumvent this challenge is conducting the reaction in acids. To this end, we here demonstrate an acid-fed membrane electrode assembly (MEA) for CO2 electroreduction to CO. A diluted electrolyte with an H+ to Cs+ ratio of 1:1 and a relatively low current density are optimal conditions to achieve high CO Faradaic efficiencies. A relatively high H+ versus Cs+ ratio offers high electrocatalytic activities. By systematically evaluating the impact of H+ and Cs+ concentration on the electrochemical performance, we uncover the essential role of the balance between the rates of (bi)carbonate formation and H+ diffusion in determining the selectivity and activity. As a result, we report a CO partial current density of ∼105 mA cm–2 at an ∼4 V cell voltage, a near-doubled activity toward CO compared to a neutral MEA at a similar voltage. Under the optimal conditions for long-term operation, our acid-fed membrane electrode assembly is capable of delivering a CO Faradaic efficiency of ∼80%, an extraordinary single-pass conversion efficiency of ∼90% (about twice that of neutral MEA), and a 50 h long-term stability notably superior to those in previous reports.

Close to 90% Single-Pass Conversion Efficiency for CO<sub>2</sub> Electroreduction in an Acid-Fed Membrane Electrode Assembly

Close to 90% Single-Pass Conversion Efficiency for CO2 Electroreduction in an Acid-Fed Membrane Electrode Assembly

Close to 90% Single-Pass Conversion Efficiency for CO₂ Electroreduction in an Acid-Fed Membrane Electrode Assembly