Direct oxidation of methanol to high value oxygenated chemicals on V2O5/TiO2 based catalysts is a green alternative to the commercial methods. But the V–Ti based catalysts are challenged by the relatively low reactivity. Herein, we demonstrated a facile and practicable strategy to directly fabricate hollow structure VOx/TiO2 nanofibers (VTO-HNF) through the coelectrospinning and calcination method. The effects of V/Ti ratio on the structure, the surface chemistry and methanol oxidation performance were investigated in detail. VTO-HNFs with appropriate V/Ti ratio have hierarchical structure, large surface area, uniform nanoparticles, narrowed grain sizes, and high dispersions of vanadium. Moreover, both the oxidation properties and the acidities of the catalyst were enhanced due to the high content of surface V4+. The VTO-HNF catalysts featured excellent activities and reliable stability for the selective oxidation of methanol to methyl formate (MF) and dimethoxymethane (DMM). The MF yield reached 90% at 150 °C, which is comparable with the noble metal based catalysts. In situ NAP-XPS investigations suggested that the variable valence of vanadium was involved in the oxidation of methanol.
A series of Sm-doped Co 3 O 4 catalysts for the N 2 O direct catalytic decomposition were synthesized by the sol–gel method using citric acid as a chelating agent and urea as a combustion agent. The doping of Sm significantly altered the activity of N 2 O decomposition on the Co 3 O 4 catalyst. Sm was incorporated into the Co 3 O 4 matrix, leading to the distortion of Co 3 O 4 lattice with the spinel configuration maintained. Sm-doping can effectively promote the oxygen vacancy generation, and the electron interaction between Co and Sm species occurred as the Co 3+ + Sm 2+ ↔ Co 2+ + Sm 3+ redox cycle. Combined with in situ Raman and in situ NAP-XPS results proposed that this redox cycle is the main reason that the Sm-doping accelerates the high-efficiency N 2 O decomposition.
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