Rh 2 O 3 /monoclinic CePO 4 composite catalysts for N 2 O decomposition and CO oxidation

Fabrication of Flower-like Rhodium-Doped β-Ni(OH)2 as an Efficient Electrocatalyst for Methanol Oxidation Reaction in Alkaline Media

In this study, β-Ni(OH)₂ with a unique flower-like morphology was synthesized through a hydrothermal method. The doping of Rh in β-Ni(OH)₂ was achieved by a reduction method. The as-synthesized catalysts were characterized by X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy for the crystal structure, morphology, composition, and chemical state analysis. The electrochemical tests revealed that the doping of Rh can significantly increase the electrocatalytic performance of β-Ni(OH)₂ in 1.0 M KOH solution. The methanol oxidation peak current density of Rh-doped β-Ni(OH)₂ reached 95 mA cm^-2 with a Tafel slope of 40 mV dec^-1. The reason for these improvements is that Rh can suppress the phase transformation of NiOOH from β to α. Meanwhile, the electronic structure change of nickel in β-Ni(OH)₂ and the defect ratio increase caused by Rh doping are beneficial to methanol oxidation reaction (MOR) catalytic activity. Furthermore, the synergistic effect between Rh and Ni(OH)₂ improved the surface activity of β-NiOOH. The doping of Rh in β-Ni(OH)₂ is initiative in this work, which provides a new strategy to design highly efficient and cost-effective MOR electrocatalysts for alkaline DMFCs.

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.

Preparation of two different crystal structures of cerous phosphate as solid acid catalysts: their different catalytic performance in the aldol condensation reaction between furfural and acetone

Liquid fuel intermediates can be produced via aldol condensation reactions through furan aldehydes and ketones driven from biomass. It was found that cerous phosphate (CP) with two different crystal structures (hexagonal and monoclinic structure), which was tailored by different hydrothermal temperature (120 °C for the hexagonal structure and 180 °C for the monoclinic structure) and calcination temperature (900 °C for the monoclinic structure) as a solid acid catalyst, exhibit high catalytic performance in aldol condensation between furfural and acetone. The CP with hexagonal structure gave 89.1% conversion of furfural with 42% yield of 4-(2-furyl)-3-buten-2-one (FAc) and 17.5% of yield of 1,5-di-2-furanyl-1,4-pentadien-3-one (F₂Ac), much higher than CP with monoclinic structure. However, both furfural conversion and aldol product yield increased from 82.3% to 96% and from 50.5% to 68.4%, respectively, for CP with the monoclinic structure after calcination owing to the higher amount of acid of catalyst after calcination but decreased continuously for CP with hexagonal structure after calcination because of its rapidly reduced BET surface area and total pore volume. The results indicated that calcination affects significantly the physical–chemical properties of CP catalysts, which influence subsequently the catalytic performance in the aldol condensation reaction. Recycling experiments showed that the catalytic performance after five number runs for CP with monoclinic structure after calcination was acceptable but was not ideal for CP with hexagonal structure owing to its poor hydrothermal stability.

Liquid fuel intermediates can be produced via aldol condensation reactions through furan aldehydes and ketones driven from biomass.