Water Oxidation to Hydrogen Peroxide Over a Super‐Aerophilic Graphite Catalyst

Abstract

Abstract Two‐electron water oxidation reaction (2e‐WOR) to produce hydrogen peroxide (H 2 O 2 ) is an attractive anode reaction with several merits. It can be paired with several large‐scale cathode reactions that produce valuable chemical substances in an electrochemical cell. However, high‐performing and reliable 2e‐WOR anodic catalysts are yet to be fully developed. In this work, a rationally designed, inexpensive, robust, and selective graphite catalyst electrode is presented, made by following the key principle mechanisms of 2e‐WOR. First, an aerophilic graphite‐based electrode is created to leverage the challenges posed by the four‐electron WOR, where the generated O 2 from this reaction is kept onto the electrode surface to shift the O intermediates binding on graphite in the direction of improved H 2 O 2 generation. An initial improvement in H 2 O 2 selectivity of seven fold is observed, albeit with no improved H 2 O 2 generation rates. The stunted H 2 O 2 generation is ascribed to poor activity from pristine graphite, courtesy of less active sites and low intrinsic O 2 binding in the electrolyte environment. Second, to improve and balance graphite's activity and selectivity, the structure of graphite is altered via different elemental doping (with N, S, B, and P atoms), a method that allows the retention of the O 2 on the graphite surface. The super‐aerophilic B‐doped graphite catalyst (optimum) reaches a maximum Faraday efficiency (FE) of 60.6 ± 2.6% with a production rate of 26.7 ± 0.6 µmol min −1 cm −2 (85.9 ± 2.2 mA cm −2 partial current density) and excellent stability of over 120 h. In tandem, cathodic H 2 co‐production is demonstrated with an FE of above 90%. This approach demonstrates a rational approach to designing inexpensive and robust 2e‐WOR anode catalysts for H 2 O 2 and the possibility of its use in chemical co‐production at the cathode.