An Ir-based anode for a practical 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.