TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Device: The fuel cell system further comprises a second adsorbent, in the housing, that is adapted to adsorb carbon monoxide from the hydrogen rich stream at low temperatures, and is adapted to desorb carbon monoxide at high temperatures. Upstream of the second adsorbent, the housing comprises a layer of a desiccant material. A preferential oxidizer is eliminated from the hydrogen fuel cell system.Preferred Method: The method is conducted in a fuel cell system having a fuel cell stack. The method further comprises pressurizing the vessel before passing the hydrogen-rich gas stream through the vessel, depressurizing the vessel after the passing of the hydrogen-rich gas stream through the vessel and purging the vessel with a gas having a low carbon dioxide concentration.Preferred Condition: The catalyst is adapted to perform the water gas shift reaction at high temperatures.Preferred Component: The housing is a pressure swing adsorber comprising multiple, staged fixed beds. The adsorbent is a first adsorbent. The hydrogen fuel cell system further comprises an expander (preferably an isothermal expander).Preferred Function: The expander provides electrical power for driving the rotating housing.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Material: The second adsorbent comprises oxides or salts of copper impregnated or exchanged on activated carbon, alumina and zeolites, oxides or salts of silver impregnated or exchanged on activated carbon, alumina and zeolites and/or oxides or salts of tin impregnated or exchanged on activated carbon, alumina and zeolites.The desiccant material comprises zeolite molecular sieves, activated alumina and/or silica gels. The carbon dioxide adsorbent comprises magnesium, calcium, manganese, lanthanum, magnesium oxide, calcium oxide, manganese oxides, lanthanum oxides and/or clay minerals. The clay minerals comprise dolomites, sepiolites and/or hydrotalcites.Preferred Component: The hydrotalcites are promoted with potassium carbonate.Preferred Function: The hydrotalcites are adapted to reversibly adsorb carbon dioxide at 300-500 degreesC.Preferred Catalyst: The catalyst is iron (II, III) oxide/chromium oxide.Preferred Condition: The weight ratio of adsorbent to catalyst is 1:20-20:1. The hydrogen-rich gas stream having reduced carbon monoxide content, is reacted in the fuel cell stack.