Fabrication of mesoporous nickel pyrophosphate electrodes and their transformation to nickel hydroxide with decent capacitance in alkaline media

The development of high-energy-density electrodes is paramount for the advancement of renewable and clean energy storage materials. In this study, we have devised a synthetic approach to fabricate mesoporous Ni 2 P 2 O 7 ( m -NiPP) electrodes with a decent charge capacity. The method involves the fo...

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Veröffentlicht in:Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2023-10, Vol.11 (41), p.22384-22395
Hauptverfasser: Ulu, I l, Ulgut, Burak, Dag, Ömer
Format: Artikel
Sprache:eng
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Zusammenfassung:The development of high-energy-density electrodes is paramount for the advancement of renewable and clean energy storage materials. In this study, we have devised a synthetic approach to fabricate mesoporous Ni 2 P 2 O 7 ( m -NiPP) electrodes with a decent charge capacity. The method involves the formation of a liquid crystalline mesophase from an aqueous solution containing nickel nitrate hexahydrate salt (Ni( ii )), pyrophosphoric acid (PPA), and a non-ionic surfactant (P123). The mesophase solidifies through the polymerization of Ni( ii ) ions and PPA, ultimately forming a mesostructured Ni 2 H x P 2 O 7 (NO 3 ) x · n H 2 O semi-solid, which can be subsequently calcined to yield mesoporous Ni 2 P 2 O 7 ( m -NiPP). The gelation and polymerization process can be monitored using gravimetric, ATR-FTIR, XRD, and POM techniques as water evaporates during the transformation. The results reveal that the reaction between the Ni( ii ) ion and PPA initiates in the solution phase, continues in the gel phase, and concludes upon gentle heating. The same clear aqueous solution can be coated onto a substrate, such as FTO or graphite rods, and then calcined at various temperatures to produce the m -NiPP electrodes, composed of spherical mesoporous NiPP particles. These electrodes remain amorphous over a wide temperature range, but crystallize at approximately 700 °C while retaining their porous structure. However, when exposed to a 3 M KOH solution, the spherical m -NiPP particles undergo a transformation into β-Ni(OH) 2 particles. These transformed particles are approximately 1.5 nm thick, equivalent to 3-4 layers, and 7 nm wide, all while maintaining their spherical morphology. This transformation process occurs rapidly for amorphous m -NiPP and proceeds more slowly in the case of crystalline m -NiPP. The resulting electrodes exhibit a substantial charge capacity of 422 C g −1 and an impressive specific capacitance of over 1407 F g −1 . A novel synthesis method has been devised to create mesoporous nickel pyrophosphate coated graphite electrodes, which undergo a chemical conversion into nickel hydroxide nanoflakes with a notable charge capacity in alkaline media.
ISSN:2050-7488
2050-7496
DOI:10.1039/d3ta05578g