Electrochemical Deoxygenation Electrolyzers Using an Organic Catalyst

Abstract An efficient oxygen reduction reaction (ORR) is crucial for deoxygenation electrolyzers. However, the use of metal catalysts in electrolyzer designs is challenging due to their high cost, catalyst dissolution, and susceptibility to poisoning. Conductive polymers have emerged as a promising new class of metal‐free catalysts for ORR, combining electron conductivity and a lack of an insulating oxidation layer. In this study, a new n‐type polymer is explored, poly(benzimidazobenzophenanthroline) (BBL), as an ORR catalyst to enhance deoxygenation efficiency in carbon‐based electrolyzers. Electrocatalytic studies show that BBL film improves ORR kinetics via a four‐electron pathway with a mass activity of the order of 100 A g ⁻¹ . A low‐voltage electrolyzer is constructed and tested using BBL‐coated carbon fiber paper (CFP) as the cathode for ORR and CFP as the anode to drive the oxidation of catechol as a compensating faradaic reaction to facilitate ORR. The deoxygenation electrolyzer with a drop‐cast BBL cathode achieves fast deoxygenation kinetics, reaching below 0.1 mg L ⁻¹ DO in salty solution with 0.001 m catechol. The findings introduce a new approach to deoxygenating thermal fluids by employing an ORR polymer catalyst and a compensating redox additive (RA) in water.