Significance Light-driven microswimmers offer prospects for autonomous microsystems. Understanding their surface catalytic processes responsible for propulsion is essential in tailoring them for specific applications. So far, photocatalytic microswimmers have been limited by the requirement of continuous illumination. Here, we report light-driven 2D carbon nitride-based Janus microswimmers, which show efficient propulsion in aqueous media not only during but also after illumination for about 30 min after 30 s prior illumination, due to so-called solar battery swimming. Contrary to the mainstream reports, we reveal oxygen reduction rather than hydrogen evolution being responsible for propulsion with alcohol fuels. Balancing reaction conditions, we report the realization of light-induced intrinsic charging of a microswimmer, enabling sustained ballistic propulsion in the dark through discharge of accumulated energy.