Photo‐Enhanced Magnesium‐Ion Capacitors Using Photoactive Electrodes

Abstract Off‐grid power sources are becoming increasingly important for applications ranging from autonomous sensor networks to fighting energy poverty. Interactions of light with certain classes of battery and capacitor materials have recently gained attention to enhance the rate performance or to even charge energy storage devices directly with light. Interestingly, these devices have the potential to reduce the volume and cost of autonomous power sources. Here, a light‐enhanced magnesium (Mg)‐ion capacitor is shown. The latter is interesting because of the large natural abundance of Mg and its ability to operate in low cost and non‐flammable aqueous electrolytes. Photoelectrodes using a combination of vanadium dioxide and reduced graphene oxide can achieve capacitance enhancements of up to 56% under light exposure alongside a 21% higher energy density of 20.5 mAh kg^‐1.