water splitting using high temperature (500°–2,000°C) which produce hydrogen & oxygen can be achieved by either concentrating sunlight or using waste heat from nuclear reactor.

artificial photosynthesis haven't been commercialized yet.

using hydrogen as fuel can probably cut on charging time & slow down battery degradation on fast charging.

using solar-powered only for car is still inefficient on current tech, need redundancy.

welp, hydrogen is unstable, maybe can take an extra step on using glucose as fuel which glucose can be turned to hydrogen+co2¯⁠\⁠_⁠(⁠ツ⁠)⁠_⁠/⁠¯