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本文报导了一个新发现的H_2置换Ni(100)面上化学吸附CO的表面反应.CO分子在Ni(100)面上的化学吸附(吸附热为126J/mole)比氢的原子吸附(吸附热为96kJ/mole)强得多,在通常条件下,H_2不能置换Ni(100)面上化学吸附的CO.但是当H_2压高于1×10~(-4)乇时,在温度为270～330K的范围内可引起H_2置换化学吸附CO的表面反应.本文用荧光产率近边吸收谱(FYNES)和程序升温脱附(TPD)对H_2置换化学吸附CO的表面反应动力学进行了详细的研究.FYNES谱在原理上与NEXAFS相同,通过测量含碳受激分子在弛豫过程中释放的碳—Kα荧光产率代替测量Auger电子产率,所以可在有气氛压力下对表面反应动力学过程进行原位考察.实验结果表明,在氢压为10~(-4)至10~(-1)乇和单晶温度为270至330K范围内,置换反应的速度公式可表示为:-dθ/dt=kθP_(H2)~(0:4)式中θ为CO的表面覆盖度,P_(H2)为气相氢压.置换反应是一个热活化过程,它随CO覆盖度的降低显示出二个不同的动力学区域,置换反应的活化能在高覆盖度下为29±4kJ/mole,在低覆盖度下为46±4kJ/mole.这比CO在Ni(100)面上的吸附热105～126kJ/mole约低75～80J/mole.本文对置换反应的控制步骤和H_2置换的机理进行了讨论
In this paper, a newly discovered surface reaction of chemisorbed CO on H 2 substitutional Ni (100) surface has been reported. The chemisorption of CO on the Ni (100) surface (adsorption heat of 126 J / mole) (96kJ / mole) is much stronger. Under normal conditions, H 2 can not displace CO adsorbed on Ni (100) surface. However, when H 2 pressure is higher than 1 × 10 -4 Torr, 330K can cause the surface reaction of chemisorbed CO with H 2 substitution.In this paper, the surface reaction kinetics of chemisorbed CO by H 2 substitution was investigated by FYNES and TPD in detail The FYNES spectra are in principle the same as NEXAFS and the surface reaction kinetics can be measured under atmospheric pressure by measuring the yield of carbon-Kα fluorescence released during the relaxation of carbon-containing excited molecules instead of Auger electron yields The experimental results show that the rate of displacement reaction can be expressed as follows when the hydrogen pressure is in the range of 10 -4 to 10 -1 torr and the single crystal temperature is in the range of 270 to 330K. / dt = kθP_ (H2) ~ (0: 4) where θ is the CO surface coverage and P_ (H2) is the vapor phase hydrogen pressure.The displacement reaction is a thermal activation process which The decrease in CO coverage shows two distinct kinetic regions with an activation energy for the displacement reaction of 29 ± 4 kJ / mole at high coverage and 46 ± 4 kJ / mole at low coverage compared to CO over Ni 100) adsorption heat 105 ~ 126kJ / mole about 75 ~ 80J / mole.In this paper, the control of displacement reaction and H_2 displacement mechanism are discussed