Electrode reactions and accumulation of hydrogen at carbon paste electrodes in the presence of tetrachloropalladate

• Published in: Journal of electroanalytical chemistry (Lausanne, Switzerland) Vol. 462; no. 2; pp. 174 - 180
• Main Authors: Lubert, Karl-Heinz, Guttmann, Markus, Beyer, Lothar
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 18.02.1999; Elsevier Science
• Subjects: Carbon paste electrode; Chemistry; Cyclic voltammetry; Electrochemistry; Electrodes: preparations and properties; Exact sciences and technology; General and physical chemistry; Hydrogen; Other electrodes; Palladium; Sorption; Tetrachloropalladate; Cyclic voltammetry; Sorption; Palladium; Tetrachloropalladate; Carbon paste electrode; Hydrogen; Chemical reduction; Adsorption; Medium effect; Electrode reaction; Proton; pH; Potassium Chlorides; Paste electrode; Experimental study; Electrochemical reaction; Carbon
• ISSN: 1572-6657; 1873-2569
• DOI: 10.1016/S0022-0728(98)00404-5

The electrochemical behaviour of the unmodified carbon paste electrode (CPE) in the presence of [PdCl 4] 2− in chloride solutions of different pH (in the range from 3 to 7) is studied by cyclic voltammetry (CV). During cathodic treatment or cycling, Pd(0) is deposited in situ on the electrode surface. Results obtained at negative potentials as a function of the concentrations of Pd(II) and protons in the solution are presented. It is concluded that hydrogen ions are reduced in different ways: first, the reduction at deposited Pd(0) or the simultaneous reduction of H + and [PdCl 4] 2−, respectively, which occurs during the whole cathodic cycle; second, the reduction in the potential range from about −0.5 to −1.0 V versus SCE, where surface groups are reduced at the unmodified CPE. The second pathway is the prevailing reduction at lower pH, which occurs at the carbon surface probably via protonated chloropalladate complexes adsorbed at the electrode surface. Potentiostatic pretreatment in the voltammetric range between 0 and +0.2 V leads in solutions of pH 5 to a pronounced increase of the H + reduction current caused by an increase of the sorption capacity of the electrode or by the accumulation of protons at the electrode surface. Protons could be accumulated at the electrode surface by formation of protonated chloropalladate complexes at the CPE.