Technoeconomic Assessment of Electrochemical Hydrogen Peroxide Production with Gas Diffusion Electrodes under Scenarios Relevant to Practical Water Treatment

Recent studies have shown that electrochemically producing hydrogen peroxide (H2O2) with gas diffusion electrodes (GDEs) directly in the water to be treated by H2O2-based advanced oxidation processes (AOPs) is problematic in practical applications because of the quick deterioration of GDE stability by oxidation with strong oxidants (e.g., hydroxyl radicals) and fouling by complex water constituents (e.g., Ca2+ and Mg2+). Therefore, this study tested the electrosynthesis of H2O2 with GDEs in electrolyte solutions in a separate reactor as an alternative for on-site H2O2 production in water treatment. Results show that many reactor configurations and operational parameters (e.g., electrode distance, current densities, electrolytes, and GDE backpressure) intertwine to have complex influences on the overall performance of H2O2 production in terms of H2O2 production rates and current efficiencies, GDE stability, operating cost, and GDE capital cost. Under optimized conditions determined in this study (4 mm electrode distance, 150–200 mA/cm2 current densities, 1 M Na2SO4, and 30 kPa GDE backpressure), ∼29,000–34,000 mg/L of H2O2 could be produced with production rates of 57.3–68.3 mg/h/cm2 and apparent current efficiencies of 55%–61% during H2O2 electrosynthesis with a divided cell, and the GDEs maintained stable H2O2 production over ∼350–1000 h before water penetrated the GDEs due to the electrocapillary effect. The operating cost, including the electricity, electrolytes, water, and oxygen consumed in the process, was ∼1.32–1.48 $/kgH2O2, and the capital cost was ∼0.30–0.46 $/kgH2O2. The results of this study suggest that it is technoeconomically feasible to scale up H2O2 electrosynthesis with GDEs in electrolytes to produce H2O2 on site in some water treatment applications, e.g., micropollutant removal in drinking water treatment by H2O2-based AOPs. Additional studies are needed to further extend the GDE lifetime by improving GDE fabrications and operations to prevent water penetration during H2O2 electrosynthesis.