The Solid-Polymer-Electrolyte Coelectrolysis of O ₂ and Water to Pure 26 wt % H ₂ O ₂ Aqueous Solutions with 81% Current Efficiency

Hydrogen peroxide is one of the essential chemicals in the industry. The H2O2 manufacture process using the anthraquinone method has a serious disadvantage of a large amount of energy consumption. Direct synthesis of pure H2O2 aqueous solutions with an 8.4 mol L–1 (26.2 wt %) concentration and 81% current efficiency was achieved by coelectrolysis of O2 and water by solid-polymer-electrolyte electrolysis. The cathode catalyst used was Ketjen black (KB)-supported 5,10,15,20-tetraphenyl-21H,23H-porphine cobalt(II) (Co-TPP), which was activated in inert gas at 1023 K, abbreviated as Co-TPP/KB(1023K), and the anode was Ti-mesh-supported IrOx. The active site of the Co-TPP/KB(1023K) catalyst (0.05 wt % Co loading) was confirmed as CoN2Cx by extended X-ray absorption fine structure (EXAFS). Essential factors for the production of H2O2 were revealed as (i) the effects of washout by water diffused from the anode compartment on the H2O2 formation at the cathode, (ii) water diffusion through the vehicle mechanism induced by the anode without ionomer modification, and (iii) the increase in activity of O2 on the cathode under pressure conditions of 11∼21 atm of pure O2.