Tailor-designed Ni-Co binary hydroxide electrodes for boosted supercapacitor applications: Smart selection of additives

• Published in: Electrochimica acta 2021-05, Vol.378, p.137991, Article 137991
• Main Authors: Abdelrahim, Ahmed M., El-Moghny, Muhammad G. Abd, El-Shakre, Mohamed E., El-Deab, Mohamed S.
• Format: Article
• Language: English
• Subjects: Additives; Co/Ni binary hydroxide film; Cobalt; Cobalt hydroxide film; Contact angle; Current density; Deposition; Electrode materials; Electrodes; Energy storage; Flux density; Graphite felt; Iodate-additives; Nanoparticles; Supercapacitors; X ray photoelectron spectroscopy
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2021.137991

•Iodate (as additive) enhances the distribution of Co(OH)2 film atop graphite felt.•Also, iodate improves the wettability of the underlying graphite felt.•Sequential deposition of binary Co/Ni(OH)2 improves the film capacitive performance.•[S, Ni, Co (1:1)] film supports superior retention of 76.6% at 30 mA cm−2. In this study, cobalt hydroxide nanoparticles-based films are electrodeposited onto high surface area graphite felt (GF), in the presence of several additives (i.e., ClO3− or IO3−), to be tested as a positive electrode for supercapacitor (SC) applications. Three films of cobalt hydroxide (Co(OH)2) are prepared from CoSO4 deposition baths, i.e., additive-free (A1), chlorate- or iodate-containing baths (A2), and (A3), respectively. The various films are characterized by employing SEM, EDX, XPS, XRD, and contact angle measurements. Film A3 (Co(OH)2 prepared in the presence of iodate as additive) shows the best performance as a positive electrode in SC applications as evident from the relevant electrochemical measurements. It supports the highest specific capacitance (567.6 F g−1 at current density 5 mA cm−2) which is retained at 82% at a high current density of 30 mA cm−2 indicating the excellent rate capability of this film. The observed high performance could be attributed to the simultaneous generation of OH− during iodate reduction enabling better distribution of Co(OH)2 throughout the GF matrix. Furthermore, a binary film is prepared by modifying film A3 via a subsequent deposition of Ni(OH)2 as a top layer. This binary modified film displays an energy density of 62.03 W h kg−1 at a power density of 2870.21 W kg−1 and the value is retained at 47.56 W h kg−1 at a high power density of 34,442.60 W kg−1 indicating the outstanding rate capability of this electrode material. [Display omitted]