Catalytic decomposition of N₂O over Au/Co₃O₄ and Au/ZnCo₂O₄ catalysts

Au/Co₃O₄ catalysts with different gold loadings were prepared by the deposition-precipitation method using HAuCl₄ solution through adjustment of the pH value to 7, 9 or 11. Their catalytic properties for N₂O decomposition in the presence of oxygen were investigated. 0.29%Au/Co₃O₄ catalyst prepared at the pH value of 9 exhibited higher catalytic activity than 0.31%Au/ZnCo₂O₄ prepared under optimal conditions although ZnCo₂O₄ was more active than Co₃O₄. AES, BET, XRD, SEM, XPS and H₂-TPR characterization results indicated a synergistic effect existed between gold and cobalt species in Au/Co₃O₄, which is, however, absent in the Au/ZnCo₂O₄. Despite that N₂O was completely decomposed at 500 ℃ in oxygen atmosphere for both the samples, the N₂O conversion was decreased to 92% and 63% after the reaction was carried out for 10 h in the presence of both oxygen and steam over the 0.29%Au/Co₃O₄ and the 0.31%Au/ZnCo₂O₄, respectively.