Dawson型磷钨杂多阴离子P2W18O626-的电化学性质和对O2还原的电催化作用

用循环伏安、交流伏安和交流阻抗法对Dawson型磷钨杂多阴离子P₂W₁₈O₆₂^6-的电化学性质进行了详细研究, 循环伏安结果显示, P₂W₁₈O₆₂^6-在pH 2.52的0.1 mol·L^-1 Na₂SO₄+NaHSO₄溶液中有两对可逆的单电子还原-氧化波和两对可逆的双电子还原-氧化波. 单电子波的峰电位和电流与溶液的pH无关, 双电子波的峰电位则随溶液pH的增加而负移, 峰电流降低, 表明双电子电极过程有H⁺参与, 其数目为2. 交流阻抗谱表明P₂W₁₈O₆₂^6-的电极过程完全受扩散控制, 实验测定其扩散系数(D_O)为2.5×10^-6 cm²·s^-1. 循环伏安结果表明P₂W₁₈O₆₂^6-的第III对波对O₂还原为H₂O₂具有显著的电催化作用, 催化效率约达300%. 将P₂W₁₈O₆₂^6-应用于PW₁₁O₃₉Fe(III)(H₂O)^4-构成的类电-芬顿过程, 使该过程对硝基苯的降解效率显著提高.

Electrochemical Properties of the Dawson-Type Heteropolytungstate Anion P2W18O626- and Its O2 Reduction Electrocatalysis

The electrochemical properties of the Dawson-type heteropolyanion P₂W₁₈O₆₂^6- were studied in detail by cyclic voltammetry, alternating current (AC) voltammetry, and AC impedance. Cyclic voltammetry results revealed that P₂W₁₈O₆₂^6- possessed two pairs of reversible one-electron redox waves and two pairs of reversible two-electron redox waves in a solution containing 0.1 mol·L^-1 Na₂SO₄ and NaHSO₄ (pH 2.52). The peak potential and the peak current of the single-electron wave were independent of the solution pH while the peak potential of the two-electron wave shifted negatively, and the peak current decreased with an increase in solution pH. This indicated that the two-electron electrode process involved H⁺ and the involved H⁺ number was 2. AC impedance spectroscopy showed that the P₂W₁₈O₆₂^6- electrode process was fully controlled by diffusion and the diffusion coefficient (D_O) was 2.5×10^-6 cm²·s^-1. The cyclic voltammograms indicated that significant P₂W₁₈O₆₂^6- electrocatalysis towards O₂ reduction to H₂O₂ occurred as evidenced by the third wave pair and a catalytic efficiency of 300% were obtained. Application of P₂W₁₈O₆₂^6- in the degradation of nitrobenzene in the electro-Fenton-like system containing PW₁₁O₃₉Fe(III)(H₂O)^4- showed a remarkable improvement in terms of degradation efficiency.