Combustion is an energetic oxidation. The primary chemical energy change is combining the oxygen with other stuff to produce stuff-oxide. If you want the stuff

Combustion is an energetic oxidation. The primary chemical energy change is combining the oxygen with other stuff to produce stuff-oxide. If you want the stuff back out in its pure form you absolutely do have to put in more energy in to remove the oxygen than the combustion result produced. Now, depending on the chemical reaction, sometimes the "more energy in" is "waaay more energy in", which can certainly be improved with catalysts and the like, but that can only create improvements like 100x to 1.1x, which is great!, but always >1.