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Au/TiO 2 (1wt% Au), Cu/TiO 2 (1wt% Cu) and AuCu/TiO 2 (1wt% AuCu) catalysts with different Au:Cu mass ratios were prepared in one-step synthesis using sodium borohydride as reducing agent. The resulting catalysts were characterized by X-ray diffraction (XRD), X-ray Dispersive Energy (EDX), Transmission Electron Microscopy (TEM) and Temperature Programmed Reduction (TPR) and tested for the preferential oxidation of carbon monoxide (CO-PROX reaction) in H 2-rich gases. EDS analysis showed that the Au contents are close to the nominal values whereas for Cu these values are always lower. X-ray diffractograms showed only the peaks of TiO 2 phase; no peaks of metallic Au and Cu species or oxides phases were observed. TPR and high-resolution TEM analysis showed that AuCu/TiO 2 catalysts exhibited most of Au in the metallic form with particles sizes in the range of 3-5 nm and that Cu was found in the form of oxide in close contact with the Au nanoparticles and well spread over the TiO 2 surface. The AuCu/TiO 2 catalysts exhibited good performance in the range of 75-100 °C and presented a better catalytic activity when compared to the monometallic ones. A maximum CO conversion of 98.4% with a CO 2 selectivity of 47% was obtained for Au 0.50 Cu 0.50 /TiO 2 catalyst at 100 o C.

Resumo: A ureia, além de estar presente na urina humana, é produzida como fertilizante em indústrias. Dessa forma, grande quantidade desse composto é lançada diariamente em efluentes. A oxidação eletroquímica da ureia é um método promissor para remoção desse composto. Assim, neste trabalho, nanopartículas de Ni suportadas em carbono e CeO 2 com diferentes morfologias, foram sintetizadas com o intuito de estudar a influência da presença do CeO 2 no processo de eletro-oxidação de ureia. As análises de difração de raios-x (DRX) revelaram a presença das fases Ni° e Ni(OH) 2 e confirmaram a presença do CeO 2 e do carbono. As imagens de microscopia eletrônica de transmissão (MET) confirmaram nanofios de CeO 2 com diâmetros de 15 nm e nanopartículas de Ni com 2 nm de tamanho. A atividade catalítica dos materiais foi investigada por experimentos de voltametria cíclica (VC) e cronoamperometria (CA), nos quais foi mostrado que a presença de céria aumentou a atividade catalítica na reação de oxidação eletroquímica da ureia. Urea, in addition to being present in human urine, is produced as a fertilizer in industries. Thus, a large amount of this compound is discharged daily into effluents. The electrochemical oxidation of urea is a promising method for removing this compound. Thus, in this work, Ni nanoparticles supported on carbon and CeO 2 with different morphologies were synthesized in order to study the influence of CeO 2 in the urea electro-oxidation process. X-ray diffraction (XRD) analyzes revealed the presence of the Ni° and Ni(OH) 2 phases and confirmed the presence of CeO 2 and carbon. Transmission electron microscopy (TEM) images confirmed CeO 2 nanowires with diameter of 15 nm and Ni nanoparticles with 2 nm in size. The catalytic activity of the materials was investigated by cyclic voltammetry (CV) and chronoamperometry (CA) experiments, in which it was shown that the presence of ceria increased the catalytic activity in the electrochemical oxidation of urea reaction.

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