# Clarification on Photodissociation

Can someone please explain what photodissociation is and if it is more efficient than electrolysis while splitting water into its components?

Photodissociation is a unimolecular reaction triggered by absorption of light. You start with one molecule, a bond (or more) breaks and you end up with two (or more) products. In water you can get $\ce{OH}$ and $\ce{H}$ (etc), usually in excited electronic states. You can not get the products of the electrolysis.
Water electrolysis is a more complex reaction. The final balance is: $\ce{2H2O -> 2H2 + O2}$, so you break four bonds and make three bonds.