Polymer electrolyte membrane (PEM) electrolysis of H2O2 from O2 and H2O with continuous on-line spectrophotometric product detection: Load flexibility studies

Hydrogen peroxide (H2O2) is a green oxidant, widely used in industry. The electrochemical production of H2O2 via the two-electron oxygen reduction reaction (2eORR) is a promising approach for the replacement of the industrial anthraquinone process because it opens the possibility to produce hydrogen peroxide using renewable energies. Classical off-line characterize techniques for the detection of hydrogen peroxide are not suitable for dynamic conditions. To quantify the efficiency of the peroxide formation we developed a novel on-line analysis setup based on the spectrophotometric analysis with titanium oxysulfate, which allows the determination of hydrogen peroxide continuously at the moment it is formed. With our setup, the concentration is continuously measured and the influence of varying process parameter can be directly monitored. We validated the setup with load flexibility experiments, were rectangular current load steps by 33.3% above and below a reference load were performed within an electrolyzer. The evolution of the hydrogen peroxide concentration was directly measurable within 35 s and 95% of the main H2O2 concentration was detectable after 2 min. The applied load steps led to no visible performance decrease of the electrolyzer and faraday efficiencies of > 98% with a maximum production rate of 122.4 mg cm-2h-1 were reached in 0.1 M H2SO4 + 0.05 M K2SO4 for current densities up to -200 mA cm-2.