Date of Award
Doctor of Philosophy
Pure (beta)-lead dioxide and lead dioxide doped heavily with other metal oxides were prepared by electrochemical deposition on a gold, rotated disc electrode (RDE) in 1.0 M HClO(,4). These electrodes were compared for their electrocatalytic support of anodic reactions accompanied by transfer of oxygen from the aqueous solvent to the reaction product. The heterogeneous rate constants of several inorganic and organic reactions were determined with emphasis on the reaction Mn(II) + 4H(,2)O (--->) MnO(,4) + 8H('+ )+ 5e;The electrocatalytic effects of numerous dopants was determined and bismuth oxide was found to cause the greatest increase in rates of anodic oxygen-transfer reactions. Physical properties of the bis- muth mixed lead oxide electrodes were examined by X-ray diffraction (XRD), Auger electron spectroscopy (AES), and scanning electron microscopy (SEM). The increased values of the heterogeneous rate constant for oxygen-transfer reactions caused by increased levels of bismuth in the mixed oxide electrodes was found to be accompanied by a decrease in the overpotential for anodic evolution of O(,2). These kinetic properties also were found to be correlated with an increasing preferred orientation of the electrodeposited mixed oxide in which the (020) plane of the slightly distorted rutile structure was oriented parallel to the geometric surface of the disc electrode. The (020) plane has the highest ratio of oxygen:metal per unit area;The greatest rate of oxidation of Mn(II), the smallest activation overpotential for O(,2) evolution, and the highest level of preferred orientation were found to occur for mixed oxides electrodeposited from solutions having a concentration ratio C('b)(,Bi(III))/C('b)(,Pb(II)) = 0.7/1.0. Mixed oxides deposited from solutions of C('b)(,Bi(III))/C('b)(,Pb(II)) (GREATERTHEQ) 1.0 were unstable and frequently became detached from the gold substrate surface during rotation in solution. It was not possible to deposit pure bismuth oxide;A general mechanistic consideration is given for anodic oxygen-transfer electrocatalysis based on the increased activity of surface oxygen at the mixed oxide electrodes; ('1)DOE Report IS-T-1303. This work was performed under contract No. W-7405-Eng-82 with the U.S. Department of Energy.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Yeo, In-Hyeong, "Anodic oxygen-transfer electrocatalysis at pure and modified lead dioxide electrodes in acidic media " (1987). Retrospective Theses and Dissertations. 11664.