金属电极上的中和滴定法——Ⅱ.不同预处理对Pt电极pH响应的影响

Neutralization Titration with Metal Electrodes Ⅱ. The Effect of Different Pretreatment on pH Response of Platinum Electrode

本文讨论了不同的预处理对Pt电极pH响应的影响。经阴极极化或火焰上红热后,Pt电极以 Pt(OH)_2+2e?Pt+2OH^-响应溶液的pH。而经+1.5V(vs.SCE)阳极极化后,由于Pt电极表面PtO_2的快速分解,电极的电位值很快下降,并逐渐达到稳定值,稳定后的Pt电极仍以上式响应溶液的pH。用KMnO_4溶液浸泡后,Pt电极表面有MnO_2沉积,并以 MnO_2+4H^++2e?Mn^(2+)+2H_2O(pH 2-7) 2MnO_2+2H^++2e?Mn_2O_3+H_2O(pH 8-12)响应溶液的pH。

The effect of different pretreatment on pH response of Pt electrode was studied. For cathodized or ignited Pt electrode, the following equation is given for the electrode process Pt(OH)_2+2e=Pt+2OH^- or PtO+2H^++2e=Pt+H_2O After anodized in 0.1 M H_2SO_4 at 1.5 V vs. SOE, Pt electrode is partially covered with PtO_2. Under open circuit condition, PtO_2 decomposes to PtO in the presence of Pt.Elec- trode potential decreases rapidly and reaches gradually the stable value. The stabilized Pt electrode also responds to pH according to the above -mentioned equation. After soaked in permanganate solution, Pt electrode is covered with MnO_2. The potential vs. pH behaviour is close to that predicted for the reactions. MnO_2+4H^++2e=Mn^(2+)+2H_2O (pH 2--7) or MnO_2+2H^++2e=Mn_2O_3+H_2O (pH 8--12)