Study of Direct Synthesis of Hydrogen Peroxide Acid Solutions at a Heat-Treated MnCl–Porphyrin/Activated Carbon Cathode from H₂ and O₂

Heat-treated MnCl–porphyrin supported on activated carbon (AC) catalyzed electrochemical reduction of O 2 to H 2 O 2 using an H 2 /O 2 fuel cell reactor. Suitable preparation conditions for an Mn–porphyrin electrocatalyst were studied for the H 2 O 2 formation, such as types of porphyrin rings, heat-treatment temperatures in He, and Mn loadings. The effects of reaction conditions, H 2 SO 4 concentration, P(O 2 ), P(H 2 ), and electrolyte flow on the H 2 O 2 formation were studied. Then, 0.5 wt % MnCl–TPP/AC heat treated at 823 K and 0.3 wt % MnCl–OEP/AC heat treated at 723 K showed good electrocatalytic activities for the H 2 O 2 formation (TPP: 5,10,15,20-tetrakis(phenyl)-21 H,23 H -porphyrin, OEP: 2,3,7,8,12,13,17,18-octaethyl-21 H,23 H -porphyrin). A maximum H 2 O 2 concentration of 1.0 mol dm –3 with 47% current efficiency (CE) was obtained under suitable conditions. The heat-treated MnCl–TPP/AC and MnCl–OEP/AC electrocatalysts were characterized using temperature-programmed desorption, X-ray absorption near-edge structure spectroscopy, elemental analysis, cyclic voltammetry, and rotating ring-disk electrode voltammetry. Elimination of Cl from MnCl–TPP and MnCl–OEP supported on AC was essential to generate an active site for the H 2 O 2 formation. A model of the Mn active site was proposed.