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• Simple synthesis of MnO2 nanostructures by hydrothermal method • Comparative ORR study for different nanostructured-MnO2 modifying Vulcan XC-72 • Highest H2O2 electrogeneration using 1% α-MnO2/Vulcan XC-72 (402 mg L-1) The electrochemical performances of the α-MnO 2 /Vulcan XC-72 and δ-MnO 2 /Vulcan XC-72 nanostructures in hydrogen peroxide (H 2 O 2) 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 H 2 O 2 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 H 2 O 2 formation were also performed. The 3% δ-MnO 2 /C and 1% α-MnO 2 /C electrocatalysts were more efficient and selective than pure Vulcan XC-72 through the ORR 2-electron pathway in the RRDE essays. Concerning H 2 O 2 electrogeneration using GDE, the 1% α-MnO 2 /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 α-MnO 2 and Vulcan XC-72, as well as oxygen functional acid species improvement, increasing electrocatalytic surface hydrophilicity and enhancing H 2 O 2 electrosynthesis. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • First-time study of magnetic field-enhanced 2-electron oxygen reduction reaction. • Investigation of different cerium oxide nanostructures on carbon Vulcan XC72. • The magnetic field shows significant improvements to conventional electrocatalysis. • Best performance with 5 % CeO 2 /C nanocubes, enhancing H 2 O 2 selectivity. • Magnetic field correlation with Zeeman effect, Lorentz and Kelvin forces, and BMP. We investigated cerium oxide nanoparticles of various morphologies (nanosheets, nanocubes, and nanoparticles) supported on carbon Vulcan XC-72 for the two-electron oxygen reduction reaction (ORR). A continuous magnetic field (2000 Oe) was used for the first time in the literature. The best results were for 5 % (w/w) CeO 2 for all three different morphologies, more than doubling the ring current, enhancing the hydrogen peroxide selectivity from 51 % (Vulcan XC-72) to 84–89 %, and modifying the onset potential to lesser negative values. The presence of the magnetic field led to even higher ring currents with 5 % (w/w) CeO 2 , H 2 O 2 selectivity from 54 % (Vulcan XC-72) to 88–96 % and changing even more the onset potential. Those results were correlated with the Zeeman effect, the Lorentz force, generating magnetohydrodynamic effects, the Kelvin force, and the formation of Bound Magnetic Polarons. This pioneering research introduces an innovative approach, highlighting the potential of an external continuous magnetic field. [ABSTRACT FROM AUTHOR]