Water dissociation on Ni(100) and Ni(111): effect of surface temperature on reactivity.
Water dissociation on Ni(100) and Ni(111): effect of surface temperature on reactivity.
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DOI：
10.1063/1.4827641
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发表时间：
2013-11
期刊：
影响因子：
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通讯作者：
H. Seenivasan;A. Tiwari
中科院分区：
文献类型：
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作者：
H. Seenivasan;A. Tiwari
利用密度泛函理论计算研究了水在Ni（100）和Ni（111）表面的吸附和解离。水吸附在Ni（100）和Ni（111）表面的顶部位置，H和OH分别吸附在Ni（100）和Ni（111）表面的四重空心和三重空心（fcc）位置。采用爬升图像微推弹性带法对两个表面的过渡态进行识别。发现Ni（100）表面的解离势垒略低于Ni（111）表面。两个表面的解离都是放热的，而Ni（100）表面的放热性较大。为了研究晶格运动对能量势垒的影响，对不同Q值（沿表面法线的晶格原子坐标）进行TS计算，并确定势垒高度和位置的变化。计算表明，反应能垒随Q的增大而减小，随Q的减小而增大。用半经典近似法计算了不同表面温度下的解离概率值。结果表明，表面温度对Ni（100）解离概率的影响明显大于Ni（111）。此外，在Ni（100）上，随着表面温度的升高，可以观察到能量势垒向较低入射能值的急剧转变，而在Ni（111）的情况下，这种转变较小。
Water adsorption and dissociation on Ni(100) and Ni(111) surfaces are studied using density functional theory calculations. Water adsorbs on top site on both the surfaces, while H and OH adsorb on four fold hollow and three fold hollow (fcc) sites on Ni(100) and Ni(111), respectively. Transition states (TS) on both surfaces are identified using climbing image-nudged elastic band method. It is found that the barrier to dissociation on Ni(100) surface is slightly lower than that on Ni(111) surface. Dissociation on both the surfaces is exothermic, while the exothermicity on Ni(100) is large. To study the effect of lattice motion on the energy barrier, TS calculations are performed for various values of Q (lattice atom coordinate along the surface normal) and the change in the barrier height and position is determined. Calculations show that the energy barrier to reaction decreases with increasing Q and increases with decreasing Q on both the surfaces. Dissociation probability values at different surface temperatures are computed using semi-classical approximation. Results show that the influence of surface temperature on dissociation probability on the Ni(100) is significantly larger compared to that of Ni(111). Moreover, on Ni(100), a dramatic shift in energy barrier to lower incident energy values is observed with increasing surface temperature, while the shift is smaller in the case of Ni(111).