Which scientific law governs why a net-positive energy system relying solely on splitting and recombining water is impossible?

Answer

The Second Law of Thermodynamics, due to inevitable energy losses.

The Second Law dictates that all energy conversions result in losses, typically as waste heat, meaning the useful energy recovered will always be less than the initial energy invested to split the water.

Which scientific law governs why a net-positive energy system relying solely on splitting and recombining water is impossible?
Chemistrywaterenergyfuelreaction