Photo-assisted charging of carbon fiber paper-supported CeO₂/MnO₂ heterojunction and its long-lasting capacitance enhancement in dark

It is important to develop green and sustainable approaches to enhance electrochemical charge storage efficiencies. Herein, a two-step in-situ growth process was developed to fabricate carbon fiber paper-supported CeO₂/MnO₂ composite (CeO₂/MnO₂–CFP) as a binder-free photoelectrode for the photo-assisted electrochemical charge storage. The formation of CeO₂/MnO₂ type II heterojunction largely enhanced the separation efficiency of photo-generated charge carriers, resulting in a substantially enhanced photo-assisted charging capability of ~20%. Furthermore, it retained a large part of its photo-enhanced capacitance (~56%) in dark even after the illumination was off for 12 h, which could be attributed to its slow release of stored photo-generated electrons from its specific band structure to avoid their reaction with O₂ in dark. This study proposed the design principles for supercapacitors with both the photo-assisted charging capability and its long-lasting retainment in dark, which may be readily applied to other pseudocapacitive materials to better utilize solar energy.