Hydrogen Peroxide Synthesis via Enhanced Two-Electron Oxygen Reduction Pathway on Carbon-Coated Pt Surface

Abstract

Continuous on-site electrochemical production of hydrogen peroxide (H2O2) can provide an attractive alternative to the present anthraquinone-based H2O2 production technology. A major challenge in the electrocatalyst design for H2O2 production is that O-2 adsorption on the Pt surface thermodynamically favors side-on configuration over end-on configuration, which leads to a dissociation of O-O bond via dominant 4-electron pathway. This prefers H2O production rather than H2O2 production during the electrochemical oxygen reduction reaction (ORR). In the present work, we demonstrate that controlled coating of Pt catalysts with amorphous carbon layers can induce selective end-on adsorption of O-2 on the Pt surface by eliminating accessible Pt ensemble sites, which allows significantly enhanced H2O2 production selectivity in the ORR. Experimental results and theoretical modeling reveal that 4-electron pathway is strongly suppressed in the course of ORR due to a thermodynamically unfavored end-on adsorption of O-2 (the first electron transfer step) with 0.54 V overpotential. As a result, the carbon-coated Pt catalysts show an onset potential of similar to 0.7 V for ORR and remarkably enhanced H2O2 selectivity up to 41%. Notably, the produced H2O2 cannot access the Pt surface due to the steric hindrance of the coated carbon layers, and thus no significant H2O2 decomposition via disproportionation/reduction reactions is observed. Furthermore, the catalyst shows superior stability without considerable performance degradation because the amorphous carbon layers protect Pt catalysts against the leaching and ripening in acidic operating conditions.