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- One-step process to form a nickel-based/carbon nanofoam composite supercapacitor electrode using Na2SO4 as an eco-friendly electrolytePublication . Della Noce, Rodrigo; Eugénio, Sónia; Boudard, M.; Rapenne, Laetitia; Moura E Silva, Teresa; Carmezim, Maria; Donne, S. W.; MONTEMOR, FATIMAIn this work, NiOx is anodically electrodeposited onto carbon nanofoam (CNF) to form a composite electrode devoted to supercapacitor applications. The use of NiSO4 as precursor in electrodeposition results in the formation of NiO and NiOOH species, as confirmed by XPS analysis, by means of a one-step anodic process. The presence of both NiO and NiOOH suggests the existence of pseudocapacitance, as observed in MnO2 and RuO2 materials. By employing Na2SO4, an eco-friendly electrolyte, the resulting composite delivers a specific capacitance of 150 F g(-1) at 1 A g(-1) considering the total mass of the electrode (deposit plus substrate). In addition, this composite electrode can operate in a very broad potential window, as high as 2.2 V, suggesting its application in high energy density electrochemical supercapacitors.
- Retaining the specific capacitance under electrochemical stress: A pH-induced self-protection mechanism for manganese dioxide pseudocapacitive electrodesPublication . Alves, Aila Cossovan; Chiavassa, Luísa; Martins, Tiago D.; Taryba, Maryna; Baleizão, Carlos; Moura e Silva, Teresa; MONTEMOR, FATIMAIn this study, we report the enhanced electrochemical performance of a MnO2 electrode modified with a pH-sensitive co-polymer, activated at acidic pH, and designed to counteract MnO2 degradation in aqueous aqueous pseudocapacitors. The conformation of this polymer is controlled by the local pH changes that occur at the electrode/electrolyte interface during electrochemical stress associated to oxygen evolution. As a proof of concept, we demonstrate that the addition of the pH-sensitive polymer contributes to improved electrode integrity and lifetime under over-polarization with oxygen evolution. After undergoing 10 cycles of electrochemical stress, the MnO2/pH-sensitive polymer composite retains similar to 70 % of its capacitance. This remarkable result stands in stark contrast with the pristine MnO2 electrode which fails catastrophically under the same stress conditions. We believe that this pH-induced self-protection mechanism represents a significant advancement in the development of novel smarter self-healing electroactive materials for the next generation of energy storage devices.