Hydrogen on Cobalt: The Effects of Carbon Monoxide and Sulphur Additives on the D2/Co(0001) System

Abstract

Hydrogen reaction on catalytic surfaces is an important field of research in fuel cell science. The adsorption of hydrogen (deuterium) on Co(0001) and the influence of carbon monoxide and sulphur on the adsorption were studied by XPS, TDS, WF measurements and LEED. The WF increased due to D2 adsorption, revealing the electronegative character of deuterium. It was found that the deuterium saturation coverage is ~0.17 ML at 320 K and ~0.27 ML at 180 K. The activation energy for desorption was estimated to be 33 kJ/mol. The coadsorption measurements with CO indicated a decrease in the deuterium yield by 50%. A downward shift of 50 K in the deuterium desorption temperature was observed as a consequence of coadsorbed CO, but changes in the CO desorption were minimal. At small CO exposures the (2 × 2) LEED structure of deuterium was seen, while at exposures of above 5 L the (2 √ 3 × 2 √ 3)R30... structure was detected by LEED as with pure CO adsorption. Coadsorption with sulphur led also to a decrease in the D2 yield leading to a complete inhibition of hydrogen adsorption at sulphur saturation. The sulphur (2 × 2) LEED structure did not undergo changes due to deuterium adsorption. As assumed, sulphur worked as a strong poison to the adsorption on Co(0001).