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

• Published in: Journal of physical chemistry. C Vol. 116; no. 7; pp. 4572 - 4583
• Main Authors: Yamanaka, Ichiro, Onizawa, Takeshi, Suzuki, Hirobumi, Hanaizumi, Noriko, Nishimura, Naoya, Takenaka, Sakae
• Format: Journal Article
• Language: English
• Published: Columbus, OH American Chemical Society 01.04.2012
• Subjects: Applied sciences; Catalysis; Catalysts: preparations and properties; Chemistry; Direct energy conversion and energy accumulation; Electrical engineering. Electrical power engineering; Electrical power engineering; Electrochemical conversion: primary and secondary batteries, fuel cells; Exact sciences and technology; General and physical chemistry; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; TDS; Heat treatment; Hydrogen peroxide; Atomic position; Cathode; XANES; Electrocatalysts; Active site; Carbon; Cyclic voltammetry; Electrolyte; Porphyrin; Rotating disk; Crystallographic site; Catalyst activity; Catalyst; Fuel cell
• DOI: 10.1021/jp207679e
• ISSN: 1932-7447

Heat-treated MnCl–porphyrin supported on activated carbon (AC) catalyzed electrochemical reduction of O2 to H2O2 using an H2/O2 fuel cell reactor. Suitable preparation conditions for an Mn–porphyrin electrocatalyst were studied for the H2O2 formation, such as types of porphyrin rings, heat-treatment temperatures in He, and Mn loadings. The effects of reaction conditions, H2SO4 concentration, P(O2), P(H2), and electrolyte flow on the H2O2 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 H2O2 formation (TPP: 5,10,15,20-tetrakis(phenyl)-21H,23H-porphyrin, OEP: 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin). A maximum H2O2 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 H2O2 formation. A model of the Mn active site was proposed.