A Novel Supercapacitor with Integrated Photosensitive Electrode to Enhance Its Capacitance Under Solar Light

This research reports a supercapacitor (SC) made with a photosensitive electrode (composed of LaFe_0.94V_0.01Mn_0.05O₃ (V-LFO) perovskite), which not only photogenerated charge by absorption of sunlight (solar cell function), but also stored charge by redox reactions (SC function). SC made with graphene (Gr) electrodes coated with V-LFO powder was named Gr/V-LFO-SC. This device produced a capacitance and energy density of 581.8 F g^-1 and 80.8 Wh kg^-1, respectively. When the photosensitive cell in the SC is illuminated with natural sunlight, the capacitance and energy density increased up to 876.9 F g^-1 and energy density of 121.8 Wh kg^-1, which represents an enhancement of ~50% for the energy density/capacitance. The enhancement was caused by the extra photogenerated electrons/holes from the Gr/V-LFO composite, which directly participated in the redox reaction process of energy-storage. In addition, the photosensitive electrode generated O₂ ^-2 and ∙OH radicals by photocatalysis (which is possible because the L-FVO powder was wet with an aqueous electrolyte), such negative ions were attracted toward the positive electrode in the SC (cathode) to be stored by EDL mechanism or these ions can directly react with the L-FVO powder to form other compounds or oxygen vacancies which also participated in the charge storage by redox reactions.