Direct catalytic decomposition of N₂O over bismuth modified NiO catalysts

Direct catalytic decomposition is a promising technology to control the emission of nitrous oxide (N₂O) during fossil fuel combustion and various chemical industries. In this study, a series of NiO catalysts modified with different metal oxides (M_aNiO_b) were prepared by the co-precipitation method and employed for the direct catalytic decomposition of N₂O. Bismuth (Bi) species was confirmed to be the most optimal promoter and the Bi_0.1NiO_1.15 catalyst with a Bi/Ni molar ratio of 0.1 exhibited the best activity over the temperature range of 300-450 °C. The addition of Bi species also promoted the steam resistance capability of the NiO catalyst. Moreover, the physicochemical properties of pure and Bi-modified NiO catalysts were further determined by several characterization methods. The surface areas and capacity of oxygen adsorption/desorption over the catalyst were noticeably improved with the doping of Bi species. Besides, the presence of doped-Bi facilitated the creation of both Ni³⁺ and surface oxygen vacancies on NiO, which promoted the performance of N₂O decomposition. Whereas, the excessive Bi species would accumulate to form large Bi₂O₃ grains, which diminished the surface areas and covered the active sites on the catalysts, leading to the rapid degradation of N₂O catalytic decomposition.