Cathodic Reduction of Dichromate Ion

[摘要] Reduction of dichromate at a platinum cathode in acid solution was studied by cyclic voltammetry and controlled potential electrolysis. Cathodic polarization curve consisted of three waves in unbuffered solution of potassium dichromate having initial pH ranges 1.5¡­4.0, with sodium sulfate as the supporting electrolyte. Relative heights of the first and the second waves were, respectively, a function of chromium (¥µ) concentration and activity of hydrogen ion, but that of the third wave was not proportional to both of them. The current of the first two peaks were proportional to the sweep rate of potential (v), while that of the last peak vs. v1/2 was linear at the sweep rate of less than 50mV/sec. By the controlled potential electrolysis, the reduction of chromium (¥µ) was almost completely suppressed at potentials more negative than the last peak and at initial pH's above ca. 2.3 of unbuffered solution. Therefore, these peaks represented, respectively, Cr2O72- ¡æ Cr3+, 2H+ ¡æ H2 and the formation of a cathodic film.

[学科分类] 化学（综合）