Surface amending effect of N-doped carbon-embedded NiO films for multirole electrochromic energy-storage devices

Abstract We synthesize N-doped carbon-embedded porous NiO electrodes using an amide-condensation reaction assisted sol-gel method for multirole electrochromic (EC) energy-storage devices. By adjusting the amount of oleylamine added to the sol solution, we simultaneously developed N-doped carbon-embedded NiO films with an optimized surface pore structure. NiO films fabricated using 2.5 wt% oleylamine (2.5OL-NiO) exhibited superior EC energy-storage performance outcomes, specifically with regard to the switching speed (coloration speed of 3.2 s and bleaching speed of 2.7 s), coloration efficiency (CE) value (48.5 cm2/C), and the specific capacitance (235.8 F/g at a current density of 2 A/g). These attractive EC energy-storage performance outcomes are primarily due to the enhanced electrochemical activity with the optimized surface pore structure. This porous film morphology was developed using evaporated H2O molecules generated from an amide condensation reaction. A second cause was the improved electrical conductivity due to the highly conductive N-doped carbon formed by means of multimeric amide condensation, which provides preferred electron pathways. Accordingly, we believe that our results present a promising electrode design strategy by which to realize multirole EC energy-storage devices.