Synthesis and Characterization of Ag−Hollandite Nanofibers and Its Catalytic Application in Ethanol Oxidation

Ag−hollandite nanofibers were synthesized through a simple hydrothermal process by oxidizing Mn(NO 3 ) 2 with AgMnO 4 in aqueous solution. The temperature was found to play an essential role in determining both the crystalline structure and the morphology of the Ag−hollandite materials, whereas the AgMnO 4 /Mn(NO 3 ) 2 molar ratio affected only the morphology of the product. Ag−hollandite nanofibers with diameters of 20−40 nm and lengths of 0.5−4 μm were prepared at 160 °C and a 2/3 AgMnO 4 /Mn(NO 3 ) 2 molar ratio. X-ray photoelectron spectroscopy surface analysis revealed that the silver species presented as Ag + and the average oxidation state of manganese was 3.9. More promisingly, the Ag−hollandite nanofibers showed quite high catalytic performance for ethanol oxidation, with ethanol conversion of 75% and acetaldehyde selectivity of 95% at 230 °C for 200 h time-on-stream. The high activity, selectivity, and stability were attributed to the stable presence of Ag + species and the unique morphology of the Ag−hollandite nanofibers.