An Ir-based anode for a practical CO2 electrolyzer

- We studied common conductive supports for oxygen evolution in neutral conditions.
- Titanium supports with iridium coating exhibited highly activity and stability.
- Stable performance was obtained using an Ir anode in a CO2 electrolyzer.

The electrochemical conversion of CO2 to fuels may provide a two-fold benefit of reducing CO2 emissions while providing of means of storing excess energy generated from renewable sources in a chemical form. Recent research focuses primarily on the development of efficient CO2 reduction electrocatalysts, while little attention has been given to the development of an effective oxygen evolution anode that is compatible for practical CO2 electrolyzers. In this report, we investigated potential anode candidates that are highly active for oxygen evolution and structurally stable under near-neutral operation conditions for a typical CO2 electrolyzer. The majority of non-precious metal-based catalysts are unstable in neutral bicarbonate electrolytes during CO2 electrolysis. In contrast, iridium-coated porous titanium electrodes exhibited decent oxygen evolution reaction activities as well as excellent stability under near-neutral conditions. Furthermore, by spray coating iridium black nanoparticles onto a cation exchange membrane (Nafion 211) and coupling it with a state-of-the-art nanoporous Ag catalyst as the CO2 reduction cathode, a remarkable total current of ∼375 mA at an applied cell voltage of 2.6 V in the span of 24 h was achieved using a 25 cm2 CO2 electrolyzer flow cell.

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