摘要
Through targeted and reproducible electrochemical treatment of glassy carbon electrodes, investigations have been carried out on the electrochemical behaviour of the oxidation of V2＋, VO2＋ and the reductions of VO2＋, VO2＋ and V3＋ in order to pretreat electrodes specifically for use in vanadium redox flow batter- ies and, if possible, to treat them in situ. For this purpose, a glassy carbon electrode was treated poten- tiostatically for a period of 30 s at different potentials in the range of 500 mV-2000 mV vs. Hg/Hg_2SO_4 in 2 M H_2SO_4 and then linear sweep voltammograms were performed in the different vanadium-containing solutions. With this method, it could be shown that all reactions are extremely surface sensitive and the reaction speeds changed by several decades. The reaction rates increased significantly in all reac- tions compared to polished electrodes and had an optimum treatment potential of approx. 1600 mV vs. Hg/Hg_2SO_4, although the oxidation reaction of V2＋ and the reduction reactions of V3＋ and VO2＋ had opposite tendencies to oxidation of VO2＋ and the reduction of VO2＋ in the area of low treatment po- tentials. In the former, the kinetics increased and in the latter, they decreased. In addition, causes were investigated using confocal microscopy and XPS. No correlation was found to the roughness or size of the stretched surfaces, although these changed significantly as a result of the treatment. XPS measure- ments gave indications of a dependence on hydroxyl groups for the oxidation of VO2＋ and the reduction of VO2＋, while for the reactions of oxygen-free cations and the reduction of VO2＋ weak indications of a dependence on carboxyl groups were obtained.
Through targeted and reproducible electrochemical treatment of glassy carbon electrodes, investigations have been carried out on the electrochemical behaviour of the oxidation of V2＋, VO2＋ and the reductions of VO2＋, VO2＋ and V3＋ in order to pretreat electrodes specifically for use in vanadium redox flow batter- ies and, if possible, to treat them in situ. For this purpose, a glassy carbon electrode was treated poten- tiostatically for a period of 30 s at different potentials in the range of 500 mV-2000 mV vs. Hg/Hg_2SO_4 in 2 M H_2SO_4 and then linear sweep voltammograms were performed in the different vanadium-containing solutions. With this method, it could be shown that all reactions are extremely surface sensitive and the reaction speeds changed by several decades. The reaction rates increased significantly in all reac- tions compared to polished electrodes and had an optimum treatment potential of approx. 1600 mV vs. Hg/Hg_2SO_4, although the oxidation reaction of V2＋ and the reduction reactions of V3＋ and VO2＋ had opposite tendencies to oxidation of VO2＋ and the reduction of VO2＋ in the area of low treatment po- tentials. In the former, the kinetics increased and in the latter, they decreased. In addition, causes were investigated using confocal microscopy and XPS. No correlation was found to the roughness or size of the stretched surfaces, although these changed significantly as a result of the treatment. XPS measure- ments gave indications of a dependence on hydroxyl groups for the oxidation of VO2＋ and the reduction of VO2＋, while for the reactions of oxygen-free cations and the reduction of VO2＋ weak indications of a dependence on carboxyl groups were obtained.
基金
the German Federal Ministry of Education and Research (BMBF) for funding the project under the number 01DR17027
