Novel Composite Material Polyoxovanadate@MIL-101(Cr): A Highly Efficient Electrocatalyst for Ascorbic Acid Oxidation

摘要

A novel hybrid composite material, PMo_(10)V2@MIL-101 was prepared by the encapsulation, of the tetra-butylammonium (TBA) salt of the vanadium-substituted phosphomolybdate [PMo_(10)V2O_(40)]_(5-) (PMo_(10)V2) into the porous metal-organic framework (MOF) MIL-lOl(Cr). The materials characterization by powder X-ray diffraction, Fourier transform infrared spectra and scanning electron microscopy confirmed the preparation of the composite material without disruption of the MOF porous Structure. Pyrolytic graphite electrodes modified with the original components (MIL-101(Cr), PMo_(10)V2), and the composite material PMo_(10)V2@MIL-101 were prepared and their electrochemical responses were studied by cyclic voltammetry. Surface confined redox processes were observed for all the immobilized materials. MIL-101(Cr) showed one-electron reduction process due to chromium centers (Cr~(III)→Cr~(II)), while PMo_(10)V2 presented five reduction processes: the peak at more positive potentials is attributed to two superimposed 1-electron vanadium reduction processes (V~V→V~(IV)) and the other four peaks to Mo-centred two-electron reduction processes (Mo~(VI)→Mo~V). The electrochemical behavior of the composite material PMo_(10)V2@ MIL-101 showed both MIL-101(Cr) and PMo_(10)V2 redox features, although with the splitting of the two vanadium processes and the shift of the Mo- and Cr- centered processes to more negative potentials. Finally, PMo_(110)V2@MrL-101 modified electrode showed outstanding enhanced vanadium-based electrocatalytic properties towards ascorbic acid oxidation, in comparison with the free PMo_(10)V2, as a result of its immobilization into the porous structure of the MOF. Furthermore, PMo_(10)V2@MIL-101 modified electrode showed successful simultaneous detection of ascorbic acid and dopamine.