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

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.