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This paper is part of an ongoing study of the structure sensitivity of ammonia adsorption on platinum. In the work here, the adsorption of ammonia on Pt ( 111) and pte 210) are compared using temperature programmed desorption (TPD), single-reflection infrared OR), electron energy-loss spectroscopy (EELS), and molecular-beam techniques. In addition, the adsorption of ammonia on pte III), (5 X 20)Pt( 100), (2 X I )Pt( 110), Pt(21O), and Pt(211) are compared with TPD. It is found that the TPD spectrum of ammonia is similar on Pt(lll), Pt(lOO), Pt ( 110), Pt ( 210), and Pt (211 ). There was always a molecular peak between 310 and 370 K, another peak at 170 K, and a multilayer peak at 120 K. The sticking probability was found to vary by a factor of 10 from Pt (210) to Pt ( III ) . However, the infrared spectrum of ammonia adsorbed on Pt (111) is virtually identical to the EELS of ammonia on Pt (210) after accounting for a difference in the sensiti vity of IR and EELS. Analysis of the TPD data indicates that the surface concentration of ammonia is a factor of 100-200 higher on Pt(21O) than on pte 111) at 670 K. By comparison, Pt(21O) was found to be at least a factor of 100 more active than pte 111) for ammonia dissociation at 670 K. There is more work to be done. However, the results so far indicate that the vaariations in sticking probability and residence time play an important role in the variations in rate.

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Das TPD‐Spektrum einer NO‐gesättigten Pt(2l0)‐Probe besitzt einen N2‐Peak bei 500 K und zwei NO‐Peaks bei′ 440 und 485 K, wobei über 70% des NO dissoziiert sind.

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