Abstract: A gas generation system comprises a reformer (1) to generate a hydrogen-containing reformate stream (4), a reformate stream cooler (2), and a shift stage (3) down-stream of the reformate stream cooler to purify the reformate stream. The surfaces of the cooler that come into contact with the reformate stream are coated with a material that contains at least one catalytically active constituent. The coating is selected such that it also protects against corrosion and sooting in the presence of oxidizing, reducing, and carbon-containing gases. By directly utilizing the coated reformate stream cooler as a catalytically active reactor unit, a water-gas shift reaction to reduce the carbon monoxide concentration takes place to some extent in the cooler prior to the reformate stream entering the actual shift stage. This enables the size of subsequent shift stage(s) to be reduced.