Oxygen Recycler

The Oxygen Recycler is a standard piece of equipment for any EVA or habitable structure which replaces Oxygen tanks, making indefinite EVA possible.

Overview
Oxygen Recyclers are cylinders three centimeters in diameter intended to fit over the carnot port of a power block. The heat from the Carnot port combined with electricity use Aluminum and heavy metal catylists to quickly convert Carbon Dioxide back into breathable Oxygen and a waste soot, which must be periodically removed. Theoretically, there's no need for an Oxygen tank with a recycler. A recycler can process Carbon Dioxide faster than a human can produce it, so the air in an EVA helmet and a person's lungs will suffice.

Disadvantages
Oxygen recyclers are able to return Oxygen quickly, but it is by all rights quite inefficient. The recycler itself sits on the power block's Carnot port because the reactions are endothermic. This makes the power block itself less effective at producing energy. A power block paired with a recycler is largely unable to provide power for any task beyond light or heat. Anyone going EVA is advised to carry two power blocks specifically so that the Recycler block can be left alone.

Larger Oxygen recyclers for ships and stations are not limited by this rule of inefficency, as that they always have spare tanks, do not need to instantly catch up to demands, and operate on such a scale that efficiency matters.