The production of dihydrogen gas via water gas shift reaction,

$\mathrm{CO}\left(\mathrm{g}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right)\underset{\text{ Catalyst }}{\stackrel{\mathrm{\Delta }}{⟶}}{\mathrm{CO}}_2\left(\mathrm{g}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right)$

The CO₂ gas is removed by scrubbing with solution of

Water gas is a mixture of carbon monoxide and hydrogen. The production of dihydrogen gas can be done by treating carbon monoxide with water. The reaction of carbon monoxide with water known as water-gas shift reaction (WGSR) and the rate of WGSR is increased using iron chromate as catalyst at 673 K.

$\mathrm{CO}\left(\mathrm{g}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right)\underset{673 \mathrm{K}}{\overset{{\mathrm{FeCrO}}_4}{\to }}{\mathrm{CO}}_2\left(\mathrm{g}\right)+2{\mathrm{H}}_2\left(\mathrm{g}\right)$

Here, the obtained carbon dioxide (CO₂) is removed by scrubbing with a solution of sodium arsenite.