Augmenting energy storage in photorechargeable supercapacitors via Ni2+/Ni3+ interconversion mechanism within TiO2/CdS/Ni2(OH)2CO3 composite photoelectrode.

Photorechargeable supercapacitors are hailed as emerging energy storage devices, capable of efficiently transforming solar energy into electrical power, offering a new potential technological pathway to meet the current societal energy demands. This work utilizes TiO 2 and CdS to construct a Type II heterojunction to enhance light absorption and promote the efficient transfer of photo-generated charges, employing Ni 2 (OH) 2 CO 3 as a pseudocapacitive active material to improve the energy storage performance of the capacitors. The NF/TiO 2 /CdS/Ni 2 (OH) 2 CO 3 composite supercapacitor exhibits excellent photo and dark capacitance performance. Under illumination, a high specific capacitance of 6730 mF cm−2 (equal to 3348 F g−1 or 418.5 mAh g−1) was achieved, which is 11.1% increment to that of under dark conditions (3013.5 F g−1) at the same current density, surpassing most of the state-of-the-art similar photorechargeable supercapacitors in previous reports. In addition, the supercapacitor maintains a capacitance retention rate of 82.3% after 2500 cycles, showing excellent charge-discharge cycle stability. Mechanistic studies indicate that during the charge-discharge process of the photorechargeable capacitor, photo-generated electron-hole pairs produced by the TiO 2 /CdS heterojunction facilitate the interconversion of Ni2+ and Ni3+ ions in Ni 2 (OH) 2 CO 3 , thereby enhancing the energy storage capability of the supercapacitor. This research provides considerable referential value for future explorations in high-capacity photorechargeable supercapacitors. TiO 2 /CdS/Ni 2 (OH) 2 CO 3 photoelectrode-based photorechargeable supercapacitor with a high specific capacitance of 6730 mF cm-2. [Display omitted] • TiO 2 /CdS/Ni 2 (OH) 2 CO 3 was fabricated for photorechargeable supercapacitor. • NF/TiO 2 /CdS/Ni 2 (OH) 2 CO 3 based supercapacitor exhibits excellent specific capacitance of 6730 mF cm−2. • excellent charge-discharge cycle stability with maintaining 91.4% capacitance retention after 800 cycles. • Machenism study reveals that the interconversion of Ni2+/Ni3+ ions plays a significant role in boosting the energy storage capability. [ABSTRACT FROM AUTHOR]