Microwave assisted synthesis of mesoporous NiCo₂O₄nanosheets as electrode material for advanced flexible supercapacitors

Abstract

Mesoporous nickel cobaltite (NiCo2O4) nanosheets are synthesized using a cost effective, ultra fast and environmentally friendly microwave assisted heating method followed by a post-calcination process of the as-prepared precursors.

Facilely Tuning Porous NiCo2O4 Nanosheets with Metal Valence‐State Alteration and Abundant Oxygen Vacancies as Robust Electrocatalysts Towards Water Splitting

“…Furthermore, accompanying with the metal valence state transition, the formation of abundant oxygen vacancies were also confirmed by O 1s core level spectra, which have been believed to play a critical role in enhancing OER performance. As shown in Figure C, three distinct peaks located at 529.6, 531.4, and 532.4 eV are observed, corresponding to oxygen atoms bound to metals, high number of defect sites with a low oxygen coordination and hydroxyl species of surface‐adsorbed water molecules, respectively . The area of the peak at 531.4 eV is substantially increased for rNiCo 2 O 4 in comparison with its counterpart, which indicates that NaBH 4 reduction is the efficient method to create stable oxygen vacancies with large amount .…”

“…As shown in Figure 3C,t hree distinct peaks located at 529.6, 531.4, and 532.4 eV are observed, corresponding to oxygen atoms bound to metals,h igh number of defects ites with al ow oxygen coordination and hydroxyl species of surface-adsorbed water molecules, respectively. [31,39,40] The area of the peak at 531.4 eV is substantially increasedf or rNiCo 2 O 4 in comparison with its counterpart, which indicates that NaBH 4 reduction is the efficient method to create stable oxygen vacancies with large amount. [30,41] Since the adsorption of H 2 Oa taC o 3 + site is more accessible for low-coordination sites, the newly generated oxygen vacancies could drastically facilitate the adsorption of H 2 Oa nd thus enhancetheir OER performance.…”

Ultrathin Mesoporous RuCo2O4Nanoflakes: An Advanced Electrode for High‐Performance Asymmetric Supercapacitors

“…The peak fitting of the Ru 3d5/2 spectra presented in this work required at least three deconvolution curves taken from ap revious report by Morgan. [36,37] The O1ss pectrum exhibits four major peaks centered at 532.5, 531.2, and 529.4 eV,a sd isplayed in Figure 1d,a ssociated with hydroxyl groups of surface-adsorbed water,surfaceoxygen ions, and metal-oxygen bonding, respectively. [30][31][32] Literatured ata are contradictory; some authors attributet he peak between2 82.5-282.8 eV to Ru in the valence state + VI, RuO3.…”

“…[29] The binding energies for the deconvolution curvesw ere 280.6, 281.9, and 282.8 eV,i ndicating the existence of Ru4 + . [36,37] Thes mall component observed at 530.8 eV suggestst hat the surfaceo fR uCo2O4 thin films is hydroxylated. [32,33] The existence of aR uO3p hase has been extensively debated in the literature.…”

The way to improve the energy density of supercapacitors: Progress and perspective

“…Generally, metal oxides are employed as one of the supercapacitor electrodes, whereby RuO 2 , MnO 2 , and Ni(OH) 2 are the most commonly used materials [38][39][40][41][42][43][44][45][46][47][48][49]. Other materials can be used as the other electrode to fabricate ASCs, such as porous carbon [50].…”