Electrolyte design for high hydrogen peroxide production rates utilizing commercial carbon gas diffusion electrodes

The electrolyte design plays a key, yet underexplored, role in the two-electron oxygen reduction reaction (2e⁻ ORR) to hydrogen peroxide (H₂O₂). Here, we investigate the dramatic beneficial impact of alkali metal cations (AMCs) on the H₂O₂ production in commercial carbon gas diffusion electrode-based flow electrolyzers in single-pass and closed-loop modes using online analytics. We demonstrate previously unavailable single-pass H₂O₂ production rates of up to 123 mg cm⁻² h⁻¹ with a Faraday efficiency (FE) of 96.9% at −200 mA cm⁻² in the presence of potassium cations, exceeding the corresponding production rate and FE in 0.1 M H₂SO₄ by a factor of 34. Additionally, to the increased selectivity, the onset potential of the 2e⁻ ORR shifted by 0.42 V toward a less negative potential. Furthermore, we explore and quantify the influence of multivalent metal cations (Ca²⁺, Mg²⁺, and Al³⁺) on the 2e⁻ ORR.