The Matter-to-Energy Converter is a theoretical device that can break down any matter into pure energy with near perfect conversion rates. It is one of the devices that can be made with sufficient Research levels, and consists of the Converter itself, and a pipe that connects to a canister or pipe system as an intake. The Converter allows you to control the rate of flow into the system, and converts whatever is input into it into power at a rate consistent with its molecular structure (hydrogen provides less power than oxygen, for example.)
A portable version can also be developed that acts as a generator, and draws minute amounts of the local atmosphere in order to produce power; it has an air filter on it that allows you to choose what to draw out of the atmosphere, also making it effectively a portable scrubber.
At the extremes of research, scientific advances may allow M2E converters to be built into power cells to create self-charging cells.