Hydrogen peroxide electrosynthesis: A comparative study employing Vulcan carbon modification by different MnO2 nanostructures

Abstract: The electrochemical performances of the {\alpha}-MnO2/Vulcan XC-72 and {\delta}-MnO2/Vulcan XC-72 nanostructures in hydrogen peroxide (H2O2) electrosynthesis were compared herein. Both materials were synthesized by a simple hydrothermal route. Their structures and morphologies were analyzed by SEM, HRTEM, XPS, Raman Scattering and XRD, and their ORR electrochemical properties and H2O2 electrosynthesis efficacies were investigated in alkaline NaOH solutions applying the rotating ring-disk electrode (RRDE) technique. Gas diffusion electrode (GDE) setups in acid media aiming at H2O2 formation were also performed. The 3% {\delta}-MnO2/C and 1% {\alpha}-MnO2/C electrocatalysts were more efficient and selective than pure Vulcan XC-72 through the ORR 2-electron pathway in the RRDE essays. Concerning H2O2 electrogeneration using GDE, the 1% {\alpha}-MnO2/C electrocatalyst displayed better activity, with peroxide accumulation of 402.6 mg/L at -1.9 V (vs Ag/AgCl) after 120 min, 48 % higher than pure Vulcan XC-72 GDE. These results can be ascribed to a synergistic effect between {\alpha}-MnO2 and Vulcan XC-72, as well as oxygen functional acid species improvement, increasing electrocatalytic surface hydrophilicity and enhancing H2O2 electrosynthesis.