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[Display omitted] • Vulcan XC-72 carbon modified with Nb 2 O 5 nanorods using the impregnation method. • H 2 O 2 generation of using Vulcan XC-72 carbon modified with 1% Nb 2 O 5 (645 mg L−1). • H 2 O 2 generation using Nb 2 O 5 /Vulcan XC-72 was 45% higher compared to pure Vulcan. • The modified material showed higher current efficiency and lower energy consumption. • Higher amount of oxygenated species, highest hydrophilicity. The production of H 2 O 2 through oxygen reduction reaction (ORR) from a 2-electron mechanism is an attractive alternative method because it allows the in-situ production of H 2 O 2 at moderate temperature and atmospheric pressure. The present study investigates, for the first time, the modification of Vulcan XC-72 carbon with niobium oxide (Nb 2 O 5) nanorods in different mass proportions (1%, 3%, 5%, and 10%) and their application as electrocatalysts in ORR through the 2-electron mechanism in alkaline media and in gas diffusion electrode for electrogeneration of H 2 O 2 in acid media. The modified electrocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), contact angle measurements, and X-ray photoelectron spectroscopy (XPS), while the ORR assays were analyzed using the rotating ring-disk electrode (RRDE) technique. The modification of Vulcan XC-72 carbon with 1% Nb 2 O 5 contributed to the enhancement of selectivity toward H 2 O 2 electrogeneration in ORR with current efficiency of 40 % higher than bare Vulcan XC-72 carbon and a relatively more positive initial potential. The application of gas diffusion electrodes for H 2 O 2 generation in acid medium using 1% Nb 2 O 5 -modified Vulcan XC-72 carbon yielded 645 mg L−1 of H 2 O 2 in 120 min of experiment at −2.5 V vs. Ag/AgCl. The concentration of H 2 O 2 electrogenerated via the application of the modified carbon material was 48 % higher compared to the concentration electrogenerated using the unmodified carbon material (444 mg L−1) under the same experimental conditions. In addition, the proposed electrocatalyst presented lower energy consumption and higher current efficiency compared to Vulcan XC-72 carbon. The results obtained can be attributed to the greater hydrophilicity of the surface of the proposed catalyst caused by the insertion of only 1% of Nb 2 O 5 nanorods. [ABSTRACT FROM AUTHOR]

• 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]

Hydrogen peroxide (H 2 O 2) stands as one of the foremost utilized oxidizing agents in modern times. The established method for its production involves the intricate and costly anthraquinone process. However, a promising alternative pathway is the electrochemical hydrogen peroxide production, accomplished through the oxygen reduction reaction via a 2-electron pathway. This method not only simplifies the production process but also upholds environmental sustainability, especially when compared to the conventional anthraquinone method. In this review paper, recent works from the literature focusing on the 2-electron oxygen reduction reaction promoted by carbon electrocatalysts are summarized. The practical applications of these materials in the treatment of effluents contaminated with different pollutants (drugs, dyes, pesticides, and herbicides) are presented. Water treatment aiming to address these issues can be achieved through advanced oxidation electrochemical processes such as electro-Fenton, solar-electro-Fenton, and photo-electro-Fenton. These processes are discussed in detail in this work and the possible radicals that degrade the pollutants in each case are highlighted. The review broadens its scope to encompass contemporary computational simulations focused on the 2-electron oxygen reduction reaction, employing different models to describe carbon-based electrocatalysts. Finally, perspectives and future challenges in the area of carbon-based electrocatalysts for H 2 O 2 electrogeneration are discussed. This review paper presents a forward-oriented viewpoint of present innovations and pragmatic implementations, delineating forthcoming challenges and prospects of this ever-evolving field. [Display omitted] • H 2 O 2 stands as one of the foremost utilized oxidizing agents in modern times. • Promising alternative pathway is the electrochemical hydrogen peroxide production. • 2-electron oxygen reduction reaction promoted by carbon electrocatalysts. • Treatment of effluents contaminated with different pollutants are presented. [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]