Nanosized nickel hexacyanoferrate modified screen-printed electrodes as flexible supercabattery platforms: Influence of annealing temperatures and supporting electrolytes

Khairy, M, Mahmoud, KG, Rashwan, FA, El-Sagher, HM and Banks, CE ORCID: https://orcid.org/0000-0002-0756-9764 (2022) Nanosized nickel hexacyanoferrate modified screen-printed electrodes as flexible supercabattery platforms: Influence of annealing temperatures and supporting electrolytes. Journal of Energy Storage, 46. p. 103872. ISSN 2352-152X

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Abstract

Water-insoluble nickel hexacyanoferrate Ni3[Fe(CN)6]2.nH2O (NiHCF) nanoparticles were synthesized via a facile precipitation method in the presence of polyvinylpyrrolidone (PVP) and sodium citrate (SC). Large-scale production of cubic NiHCF crystals with an average diameter of 35 nm and a specific surface area (SBET) of 452.9 m2/g was shown to be possible. The NiHCF nanoparticles were drop-cast upon screen-printed graphite macroelectrode surfaces (SPEs) allowing a flexible energy storage device to be realised. The tunable pore size and dual functional reactive sites offered superior specific capacitances of 197.5, 139.35, 356.25, and 406.25 F/g in 0.1 M KCl, 0.1 M NaCl, 0.1 M NaOH and 0.1 M KOH, respectively at a current density of 5 A/g. The highest capacitance was found using 0.1 M KOH supporting electrolyte due to the combination of surface (intercalation/de-intercalation of A+) and faradaic processes (M2+/M3+) as supercabattery platforms. The thermal treatment of the NiHCF samples at 100, 200, 300 °C were performed within oxygen and nitrogen atmospheres and the specific capacitances were measured in 0.1 M KOH. Interestingly, the specific capacitance increases up to 546 F/g for NiHCF annealed at 100 °C in oxygen and reduces to 342 F/g if NiHCF when annealed at 200 °C in nitrogen atmospheres due to the likely introduction of diverse vacancies. Furthermore, the NiHCF/SPEs were investigated in an as-symmetric two-electrode system, which revealed a specific capacitance of 570 F/g at 5 A/g. The NiHCF/SPE exhibited high capability rate, capacitive retention and excellent cycling stabilities particularly if NiHCF was annealed within a nitrogen atmosphere. Thus, the NiHCF supercabattery platforms can be used for developing new flexible energy storage devices.