Ink formulation and electrolytes affect electrochemical oxygen reduction into H₂O₂: a kinetic study

The electrocatalytic production of hydrogen peroxide (H₂O₂) through the 2-electron oxygen reduction reaction (2e ORR) has garnered significant research interest as an appealing alternative to the conventional anthraquinone process. To advance industrial applications, carbon materials emerge as one of the most promising catalysts for the 2e ORR. The evaluation of their electrochemical activity and selectivity is the most fundamental of research in this field. However, tremendous studies have been reported by using various ink formulations and electrolytes, neglecting their underlying influences on apparent ORR kinetics. By employing carbon black as the model catalyst, this study investigates the impact of ink formulations, catalyst loading, and electrolytes on the efficiency and selectivity of the 2e ORR. Results indicated that an optimal ink formulation containing 10 μL of Nafion and 1000 μL of alcohol exhibited superior efficiency for H₂O₂ generation. Moreover, the optimal H₂O₂ generation over a gas diffusion electrode can be acquired with a current density of 0.8 mA cm^-2 and an electron transfer number of 2 under a catalyst loading of 0.1 mg cm^-2. Besides, the linear correlation between transferred electron numbers and electrolyte concentrations indicates that the ideal 2e ORR can be achieved in 0.98 mol L^-1 KOH. This study describes the effects of carbon-based electrode preparation methodologies and offers basic insights into the electrochemical synthesis of H₂O₂.