Abstract:

MnO_x nanoparticles obtained by the emulsion method were loaded on a microporous tubular titanium membrane to prepare a functional MnO_x/Ti electrocatalytic membrane. The effects of calcination temperature on the crystal structure of MnO_x as well as the electrochemical properties and catalytic performance to oxidize benzyl alcohol of MnO_x/Ti membrane were systematically investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), cyclic voltammetry (CV), chronoamperometry (CA), and other characterization methods. The results indicated that the crystal structure of MnO_x was gradually transformed from Birnessite-MnO₂ to K_0.27MnO₂, and finally to α-MnO₂ from Mn3O4 with increasing calcination temperature. The α-MnO₂ particles in the MnO_x/Ti electrocatalytic membrane showed high crystallinity and uniform particle size (less than 30 nm). The superior electrochemical properties and catalytic performance of α-MnO₂/Ti membrane obtained at a calcination temperature of 450 ℃ could be attributed to the binding effects between unsaturated coordination atoms of Mn and oxygen vacancies with the Ti substrate. The α-MnO₂/Ti membrane obtained at 450 ℃ was used as the anode to assemble an electrocatalytic membrane reactor to oxidize benzyl alcohol. 64% conversion of benzyl alcohol and 79% selectivity to benzaldehyde was achieved under the operating conditions: reaction temperature 25 ℃, aqueous benzyl alcohol solution of 50 mmol·L^-1, current density 2 mA·cm^-2, and residence time 15 min.

Key words: Porous titanium membrane, Electrocatalytic membrane reactor, Manganite, Benzyl alcohol, Catalytic oxidation