Electrochemical impedance spectroscopy investigation of spinel type cobalt oxide thin film electrodes in alkaline medium

Abstract

Spinel type Co 3 O 4 thin films, for the oxygen evolution reaction (OER) in 1 M KOH, have been prepared, on stainless steel supports, using the thermal decomposition method at 400°C. The electrochemical behaviour of the oxide film/1 M KOH interface was investigated by cyclic voltammetry and impedance techniques. The impedance measurements were carried out at different positive potentials, from the open circuit potential to a potential in the OER region and the electrical equivalent circuit, L (R 1 Q 1 ) (R 2 Q 2 ) (R 3 Q 3 ) was used to fit the experimental results. At each potential, a good correlation between experimental and simulated data is found, thereby validating the proposed equivalent circuit model. The roughness factor value determined in the potential region where the charge transfer reaction is negligible is similar to that obtained by cyclic voltammetry, with a value of 70 ± 2.

Original Conductive Nano-Co3O4 Investigated as Electrode Material for Hybrid Supercapacitors

“…In addition, the average oxidation state of cobalt is higher in this nano-material (2.81) than in the ideal spinel (2.67), which was correlated to the presence of Co 4þ ions. 15,21 On the basis of these results, and if it is assumed that H and Li are in tetrahedral sites, according to similar results obtained on micrometric cobalt oxides, 21 According to this formula, proton and lithium ions are too numerous to be only located in the vacant tetrahedral sites of the spinel struc-ture (0.25/molecule), and might also occupy the other tetrahedral sites of the cubic structure (8b or 48f). Anyway, it should be noticed that this material exhibits nanometric dimensions, with a large amount of atoms at the surface of particles, so that the formula can only be considered as an average over the whole powder.…”

Timely-activated 316L stainless steel: A low cost, durable and active electrode for oxygen evolution reaction in concentrated alkaline environments

“…One widely-used strategy to prepare stable OER electrocatalysts is to deposit a thin "active layer" of these metals/oxides on the surface of an electronically conductive substrate, e.g. carbon [38,47], conducting oxides [9,[49][50][51][52][53][54][55] or steels [56][57][58][59]. Although electrocatalysts prepared on such electrodes can be very active, their long-term durability is rarely reported and is open to question, in particular in strong bases: except from Li's work [60], dealing with Janus Ni-Co-P nanowires, which were demonstrated for 3000 h in water electrolysis, durability studies of the literature usually do not exceed a few 10 or at best a few 100 of h in operation for such electrocatalysts.…”

Influência da composição de catalisadores de Pt e Ru na reação de eletro-oxidação de propanodiol

“…Além disso, observa-se também o aumento da carga voltamétrica do eletrodo binário quando comparado ao eletrodo de Pt100/Ti. De acordo com Laourni et al [4], este aumento de carga voltamétrica observado para o eletrodo de Pt50Ru50/Ti pode ser atribuído a combinação dos dois elementos metálicos, o que provoca um aumento na quantidade de poros e trincas na superfície do eletrodo, influenciando diretamente na atividade catalítica deste material.…”