硝酸根电化学还原去除过程阴极电位振荡研究

硝酸根在电化学还原去除过程中存在多价态变化行为,该过程是一个典型的远离平衡态的非线性体系.为探明硝酸根在去除过程中发生的电化学行为,研究了H₂SO₄浓度、电流、反应温度及NO₃^-浓度对阴极电位振荡的影响规律.采用循环伏安法、XRD、SEM-EDS及XPS表征方法,分析了反应体系循环伏安特性,以及反应前后阴极Cu表面的物相组成、微观形貌、表面电子价态等变化规律.研究结果表明,在恒流条件下(Pt作为阳极、Cu作为阴极),H₂SO₄-NaNO₃体系发生了明显的电位振荡;当H₂SO₄浓度为0.10mol/L,电流为12mA,温度为20℃,NaNO₃浓度为0.20mol/L最佳电位振荡条件下,振荡平均振幅为1.15V,振荡平均周期为3s.另外,硝酸根在电化学还原去除过程产生的周期性电位振荡主要原因是阴极Cu表面生成的致密CuO薄膜不断溶解和形成,以及阴极表面H₂的周期性产生与消失.

Potential oscillation of cathode in nitrate electrochemical reduction removal process

Nitrate has a polyvalent behavior in electrochemical reduction removal process, it is a typical nonlinear system far from equilibrium. To investigate the electrochemical behavior of nitrate during the removal process, the influence of H₂SO₄ concentration, current, reaction temperature and NO₃^- concentration on cathode potential oscillation was systematically studied. The cyclic voltammetry characteristics of the reaction system and the changes of the phase composition, microstructure and surface electron valence state of the cathode Cu surface before and after the reaction were analyzed by cyclic voltammetry, XRD, SEM-EDS and XPS. The results show that the H₂SO₄-NaNO₃ system had obvious potential oscillation under constant current conditions (Pt as anode and Cu as cathode). When concentration of H₂SO₄ and NaNO₃ were separately 0.10, 0.20mol/L, the current 12mA, the temperature 20℃, the oscillation average amplitude was 1.15V and the oscillation average period was 3s. In addition, the periodic potential oscillation of nitrate in the process of electrochemical reduction removal was mainly caused by the continuous dissolution and formation of the dense CuO film on the Cu surface of the cathode, and periodic generation and disappearance of H₂ on cathode surface.