The Electrochemical Engineering of Anodic Peroxide Production in Alkaline Water Electrolysis

Abstract

With increasing climatic changes due to greenhouse gas accumulation, there is an urgent need for sustainability improvements across many sectors of society, including chemicals manufacturing. One ubiquitous chemical feedstock in need of a cleaner production method is hydrogen (H2), commonly produced by the environmentally unfriendly steam-methane reforming reaction. The production of H2 could be made far more sustainable by instead using alkaline water electrolysis powered by renewable energy, but the process economics are unfavorable, with so-called “green” hydrogen from water electrolysis costing much more than less sustainable “gray” hydrogen. The majority of the costs of green hydrogen arise from the balance of plant surrounding the electrolyzer, and recent research has made only incremental progress in improving the efficiency of either the balance of plant or the electrolyzer itself. Driving down the cost of green hydrogen will require a more innovative approach. Electrolysis splits water into high-value H2 but also low-value oxygen (O2). A creative approach to lowering costs would be to replace the anodic reaction producing low-value O2 with a reaction to produce high-value hydrogen peroxide (H2O2). The H2O2 could then be separated and sold, offsetting the higher cost of the green hydrogen produced at the cathode. This method of paired electrolysis to simultaneously produce H2 and H2O2 has been the subject of much study with respect to its electrochemistry, but very little with regards to the electrochemical engineering. If we are to scale this reaction and offset the cost of green hydrogen by co-production of a valuable side product, we also need to understand the electrochemical engineering of the reaction, from the scale of operational devices to the complete process plant....