Abstract
The production of H2O2 through oxygen reduction reaction (ORR) from a 2-electron mechanism is an attractive alternative method because it allows the in-situ production of H2O2 at moderate temperature and atmospheric pressure. The present study investigates, for the first time, the modification of Vulcan XC-72 carbon with niobium oxide (Nb2O5) 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 H2O2 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% Nb2O5 contributed to the enhancement of selectivity toward H2O2 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 H2O2 generation in acid medium using 1% Nb2O5-modified Vulcan XC-72 carbon yielded 645 mg L−1 of H2O2 in 120 min of experiment at −2.5 V vs. Ag/AgCl. The concentration of H2O2 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 Nb2O5 nanorods.
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