Deoxo (Catalytic Deoxidation)

In plain terms

Hydrogen leaving an electrolyzer is wet and carries a trace of oxygen that has crossed the separator. Most end uses tolerate very little oxygen, so it must go.

A deoxo reactor passes the gas over a catalyst bed. There, oxygen combines with a small amount of the hydrogen to form water:

2 H₂ + O₂ → 2 H₂O

The reaction gives off heat, so the gas leaves warmer, and a little hydrogen is consumed in the process.

Why it sits before the dryer. Deoxo turns oxygen into water. Placing it upstream of the dryer means the dryer removes both the original moisture and the water the deoxo creates in one step. Reversing the order would put fresh water back into gas that had already been dried. Published purification trains use this order, with the oxygen-removal tower upstream of the dryer (Kwon et al., 2023).

Typical range

Inlet oxygen content depends on electrolyzer technology and load, because crossover rises at part load (Brauns and Turek, 2020). Outlet targets follow the purity grade required.

On a commercial 50 kW alkaline electrolyzer, the main impurities in the hydrogen were nitrogen, oxygen and water. One catalytic step removed the oxygen, and after drying the product met ISO 14687 (Ligen et al., 2020).

Why it moves LCOH

Deoxo is a small CAPEX item, but it consumes some product hydrogen and adds a step between production and delivery. Its real cost effect is indirect: it is one of the losses that make delivered hydrogen lower than stack output.

Common mistake