Estudo Comparativo do Efeito da Morfologia da Céria Suportada em Carbono na Reação de Redução de Oxigênio (RRO)

Ceria is a oxide with good electrocatalyst properties to RRO via 2 electrons, as presented in previous works [1]. This work aims to study the effect of the ceria(CeO2) morphology supported on carbon (Printex 6L) in different proportions for the in situ H2O2 production. CeO2 nanorods (NR) were synthesized by the hydrothermal method [2] and supported on carbon by an impregnation method, while the nanoparticles (NP) were prepared bythe polymeric precursor method (PPM) [1]. Samples containing 1%, 2.5%, 4%, 5.5% and 10% of ceria on carbon were studied using a rotating ring-disc electrode (RRDE) for ORR in basic media. The working electrode is a glassy carbon disc (area = 0.2475 cm2), where the electrocatalyst film was deposited, with a gold ring (area= 0.1866 cm2). It was used platinum (area= 2 cm2) as counter electrode and an Hg/HgO reference electrode. The experiments were performed in NaOH 1 mol.L-1 [3], with the disc anode scan from 0.1V to -0.6V and the ring polarization at 0.3V in different rotations 100, 400, 625, 900 and 1600 rpm. The 1600 rpm was the rotation used for the calculation the number of electrons transferred. From the data obtained in this analysis it was possible extract the necessary values to calculate the number of electrons transferred [3]and the hydrogen peroxide production (as well, water generation) percentage by each electrocatalyst tested, and this number is showed in Table 1 for both the best materials and the reference ones. With the results obtained, we can conclude that the CeO2 nanoparticles supported on Printex 6L are better for the hydrogen peroxide production than the CeO2 nanorods and pure Printex 6L, probably because it has a greater number of defects in its structure, thus resulting in a greater favoring of its catalytic activity for H2O2 production.