Catalyst-less efficient electrochemical production of hydrogen peroxide

Abstract

Hydrogen peroxide is produced efficiently in a catalyst-less electrochemical cell manufactured at lab scale (4 cm2 of electrode size) by resin and titanium 3-D printing. The electrolyte inlet and outlet of the cell are designed to promote a very turbulent flow pattern that provides good mixing of the liquid and gas phases and minimizes the mass transport limitations. The mechanization of the titanium contributes to an efficient gas diffusion in the cathode which was successfully adapted to the 3-D printed cell resulting in a very efficient gas–liquid reactive absorbent unit. The effect of the electrolyte, operation mode, gas and liquid flow rates were evaluated on the electrochemical production of hydrogen peroxide and the results obtained were successfully fitted to a simple phenomenological model that helped to obtain a deep understanding of the process. The proposed electrochemical gas–liquid absorber achieved coulombic efficiencies as high as 69.72 % and energy consumptions close to 9 mg H2O2 (Wh)−1 when the system was operated in continuous mode with the most efficient conditions (no cell compartmentation and feeding pure oxygen with electrolytes containing sulphate salts at pH near 3). Those values of efficiencies are in the upper range of the results found in the literature for the electrochemical production of hydrogen peroxide, even though no catalytic coating was used to promote this cathodic reaction. An unexpected effect of the salt contained in the electrolyte was observed indicating the existence of other production mechanisms that require further characterization.