Mechanism for the Formation of Black Cr-Co Electrodeposits from Cr3+ Solution Containing Oxalic Acid

作者：Choi Yun Il^*; Eguchi Takuhiro; Asao Takayuki; Kuroda Kensuke; Okido Masazumi

来源：Journal of the Electrochemical Society, 2014, 161(14): D713-D718.

DOI：10.1149/2.1091412jes

One possible mechanism for the growth of Cr-Co electrodeposits from 1.0MCrCl(3) center dot 6H(2)O + 0.1MCoCl(2) + 0.5MH(2)C(2)O(4) at 25 degrees C was proposed based on the results of careful EQCM, XPS, TEM, HRTEM, and EELS analysis. During the initial electrodeposition time, the Co2+, which is nobler than Cr3+, preferentially nucleates and grows perpendicular to the electrode surface, although arborescent patterns soon appear and further ramify with thinner, bent branches over time. This bulk encapsulating structure can easily trap the OH- ions formed by cathodic hydrogen evolution, thereby retarding the diffusion and further increasing the pH of the solution. This may accelerate the formation of Cr2O3 throughout most of the metallic-Co-free zone.

• 出版日期2014