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Journal of the Korean Chemical Society (JKCS)

ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 18, Number 2
JKCSEZ 18(2)
April 20, 1974 

A Study of Cathodic Reduction of Chromate Ion on Platinum

백금전극에서 크롬산염이온의 음극환원반응에 관한 연구
Kum Sho, Hwang

백금전극을 사용해서 CrO4=이온의 환원을 중성인 비완충용액과 pH 8∼10 범위의 완충용액 및 강한 알카리성용액에서 조사하였다. pH 8∼10 범위의 완충용액에서 CrO4=이온의 환원에 관여한 전하이전의 수는 pH가 증가하므로써 점점 증가되었다. CrO4=이온dl 0.2N NaOH 용액에서 환원되어 질때 반응기구가 다음과 같이 가정되었다. CrO4=+H2O+2e→CrO3=+2OH-, CrO3=3H2O+e→Cr(OH)3+3OH- pH 13.5이고 지지전해질인 (CH3)4NOH 용액에서 CrO4= 이온이 환원되어 질때 두째번 파에서 심한 흡착을 보여주었다. 0.1N KCl의 비완충용액에서 linear sweep voltammogram은 initial voltage와 voltage sweep rate에 따라 세개 혹은 네개의 분명한 파로 나타나지만 첫째번 파는 확산에 의해서만 된 파라고 설명하기에는 어려움이 있었다.

Reduction of chromate ion at the Pt-electrode was investigated in neutral unbuffered solutions, in buffered solutions of pH between 8 and 10, and in strongly alkaline medium. In buffered solutions of pH between 8 and 10, the number of electrons transfered in the reduction of chromate ion increased progressively with increasing pH. When chromate ion was reduced in 0.2 N sodium hydroxide medium the following mechanism was suggested: CrO4= + H2O + 2e → CrO3= + 2OH-, CrO3= + 3H2O + e → Cr(OH)3 + 3OH- When tetramethylammonium hydroxide (pH=13.5) was used as the supporting electrolyte, a second wave indicated strong adsorption. In unbuffered solutions of 0.1 N potassium chloride the linear sweep voltammogram consists of three or four distinct waves depending on the initial voltage and the voltage sweep rates, but the first wave was difficult to explain as a diffusion controlled wave.

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