Electrochemically Triggered Self‐Adaptive Reconstruction of an all‐Purpose Electrode for Photothermally Enhanced Capacitors

Abstract Large‐capacity energy storage devices are attracting widespread research attention. However, the decreased capacity of these devices due to cold weather is a huge obstacle for their practical use. In this study, an electrochemical self‐adaptive reconstructed Cu x S/Cu(OH) 2 ‐based symmetric energy storage device is proposed. This device provides a satisfactorily enhanced photothermal capacity under solar irradiation. After electrochemical reconstruction treatment, the morphological structure is rearranged and the Cu x S component is partially converted to electrochemically active Cu(OH) 2 with the introduction of a large number of active sites. The resulting Cu x S/Cu(OH) 2 electrode provides a significant capacitance of 115.2 F cm −2 at 5 mA cm −2 . More importantly, its wide working potential range and superior photo‐to‐thermal conversion ability endow Cu x S/Cu(OH) 2 with superb performance as full‐purpose photothermally enhanced capacitance electrodes. Under solar irradiation, the surface temperature of Cu x S/Cu(OH) 2 is elevated by 76.6 °C in only 30 s, and the capacitance is boosted to 230.4% of the original capacitance at a low temperature. Furthermore, the assembled symmetric energy storage device also delivers a photothermal capacitance enhancement of 200.3% under 15 min solar irradiation.