Insight into the mechanism of the dopant-defect engineering for improving MnCo2O4-based photo-assisted supercapacitor performance

Designing appropriate semiconductors for photo-assisted supercapacitor serves as a promising means to maximize solar energy use. The efficiency of photogenerated carrier separation is a key to improving the energy storage performance of semiconductor-based photoelectrodes. In this study, we applied dopant-defect engineering to fabricate MnCo 2 O 4 with N doping and oxygen vacancies containing (N-Ov-MCO) for use as a photo-assisted supercapacitor electrode. N doping promoted the generation and effective separation of photogenerated electron-hole pairs under light. In addition, the formed oxygen vacancy facilitates OH − adsorption on the N-Ov-MCO surface combined with DFT simulation findings. As a result, the specific capacitance of N-Ov-MCO (567.25 F g −1 ) at 1 A g −1 under illumination is 1.28 times greater than that of the original MCO. A red LED shone brighter under light when three N-Ov-MCO-based devices (N-Ov-MCO//AC) were linked in series, which demonstrated its practical potential. In the N-Ov-MCO//AC, the photogenerated electrons were introduced into the circuit via nickel foam, which aided in the charging process and the photogenerated holes along with OH − were involved in in the oxidation process. This study revealed that dopant-defect engineering efficiently improves the photo-assisted supercapacitor performance and offers a basis for the theory on practical applications.