Direct access to NiCo-LDH nanosheets by electrochemical-scanning-mediated hydrolysis for photothermally enhanced energy storage capacity

With the wide application of supercapacitors, it has been recognized that the drop of energy storage capacity due to cold environmental temperatures limits their utilization efficiency. In this study, a binder-free Ni/Co-layered double hydroxide (LDH)-based high-performance energy storage device is constructed on Ni foam by in situ electrochemically triggered MOF hydrolysis, which exhibits a remarkably enhanced capacity under solar irradiation. Through electrochemically controlled hydrolysis, the ligands in MOFs are replaced by OH–, and the obtained NiCo-LDH retains the original hierarchical porous structure of the MOFs. Benefitting from the sufficient oxygen vacancies and large surface area, the NiCo-LDH electrode shows a high capacity of 5.4 C cm–2 at 1.25 mA cm–2, which is 64.3 times higher than that of the MOF template. Importantly, the excellent photothermal conversion ability (temperature increase of 52.9 °C within only 30 s) under solar irradiation increases the capacity to 226.0% even at sub-freezing temperature. Furthermore, the asymmetric supercapacitor fabricated using NiCo-LDH delivers an energy density increase of 329.2% in a low-temperature environment (−4 °C) after 15 min solar-light irradiation.