Bifunctional nanoparticles decorated Ni _1‐x Mn _x Co ₂ O ₄ ultrathin nanoflakes‐like electrodes for supercapacitor and overall water splitting

Abstract

Synthesizing triple transition metal oxide (TTMO) is an extraordinary strategy to develop electrodes for efficient energy storage and conversion devices, owing to their unique nanostructure with high porosity and specific surface area. The cobalt-based mixed-valence oxides have attracted great attention due to their facile synthesis, low cost, and excellent electrochemical performance. However, less attention is paid to investigating the effect of different substitutions on the physico-chemical properties of TTMO. In this study, nanoparticles (NPs) decorated ultrathin Ni 1-x Mn x Co 2 O 4 nanoflakes (NPs@NFs) are synthesized by tuning the molar ratio between Mn and Ni via facile deep eutectic solvents (DESs) method. Unique and highly porous NPs@NFs nanostructures aid to increase the overall surface area of the materials, whereas Mn, Ni, and Co ions participate in their redox-active capacity, improving the electrochemical activity of the material. This Ni 0.8 Mn 0.2 Co 2 O 4 hybrid nanostructure exhibited excellent supercapacitive performance with a high specific capacity (Cs) of 761 mAh g À1 at a higher current density of 30 mA cm À2 and superior cycling retention of 92.86% after 10 000 cycles. Further, a hybrid asymmetric supercapacitor (Ni 0.8 Mn 0.2 Co 2 O 4 //AC) device exhibited an extended potential window of 1.5 V, which results in an ultrahigh energy density of 66.2 W kg À1 by sustaining a power density of 1519 Wh kg À1 . The electrocatalytic activity of the optimized Ni 0.8 Mn 0.2 Co 2 O 4 shows the outstanding performance toward hydrogen evolution reaction (HER) (150 mV/ 161 mV dec À1 ) and oxygen evolution reaction (OER) (123 mV/47 mV dec À1 ) with a lower voltage of 1.51 V (@10 mA cm À2 ) for overall water splitting, with outstanding stability up to 25 hours. These results indicate that chemically synthesized ultrathin

Deep eutectic solvents as green solvents for materials preparation

“…In Shinde's study, nanoparticle-decorated ultrathin Ni 1− x Mn x Co 2 O 4 nanosheets (NPs@NFs) were bottom-up synthesized by adjusting the molar ratio between Mn and Ni in the DES. 196 The unique and highly porous NPs@NFs nanostructure helps to increase the overall surface area of the material, while Mn, Ni, and Co ions constitute its redox activity ability, thereby enhancing the electrochemical activity of the material. This Ni–Mn–Co 2 O 4 hybrid nanostructure exhibits excellent performance with a high specific capacity of 761 mA h g −1 at a relatively high current density of 30 mA cm −2 and a cycle-retained rate of 92.86%.…”

Plasma-Engineered N-CoOx Nanowire Array as a Bifunctional Electrode for Supercapacitor and Electrocatalysis

“…Since energy storage and electrocatalysis depend on the heterogeneous reactions that occur on the surface of active materials, surface engineering, including doping [ 13 , 14 ], morphology modification [ 15 , 16 ], preferential facet growth [ 17 , 18 ], defect engineering [ 19 , 20 ], and heterojunction construction [ 21 , 22 ], has been applied as a popular strategy to improve the performance. Among various strategies, morphology modification can directly affect catalytic activity via surface structure regulation, which varies in terms of active reaction area, ion transport and surface energy.…”