Energetics of Adsorbed Formate and Formic Acid on Cu(111) by Calorimetry
Energetics of Adsorbed Formate and Formic Acid on Cu(111) by Calorimetry
复制标题
DOI：
10.1016/j.jcat.2017.05.023
复制
发表时间：
2017-08
期刊：
影响因子：
12.9
通讯作者：
Wei Zhao;S. Carey;S. E. Morgan;C. Campbell
中科院分区：
文献类型：
--
作者：
Wei Zhao;S. Carey;S. E. Morgan;C. Campbell
表面羧酸盐是许多催化反应中常见的中间体，也用于表面的有机官能化。在此，吸附甲酸，最简单的羧酸，通过解离吸附在Ni（111）表面上的甲酸和吸附热的单晶吸附量热法（SCAC）测量。在240 K时，在1/7 ML下，使吸附的双齿甲酸盐和吸附的氢解离吸附的积分热为117.1 kJ/mol。测量热量的估计精度在3 kJ/mol以内。因此，双齿甲酸根在Ni（111）上的标准生成焓为−449.3 kJ/mol，与Ni（111）表面的键合焓为319.6 kJ/mol。与我们先前对Pt（111）的结果相比，双齿甲酸盐在Ni（111）上更稳定54 kJ/mol。这是第一次实验测量通过金属-氧键结合到任何Ni表面的任何分子片段的能量，因此它是验证Ni催化剂上广泛吸附的含氧化合物的量子力学计算准确性的重要基准。与以往的密度泛函理论（DFT）计算相比，我们发现DFT计算系统地低估了甲酸根与Ni（111）的键能，但正确地预测了甲酸根与Ni（111）的键能比与Pt（111）的键能强。在0.45 ML和120-155 K下，测定了甲酸吸附成分子吸附态的积分热为63.2 kJ/mol。
Surface carboxylates are common intermediates in many catalytic reactions and are also used for organo-functionalization of surface. Herein, adsorbed formate, the simplest carboxylate, was produced by dissociative adsorption of formic acid on the Ni(111) surface and the heats of adsorption were measured by single-crystal adsorption calorimetry (SCAC). At 240 K, the integral heat of dissociative adsorption to make adsorbed bidentate formate and adsorbed hydrogen is 117.1 kJ/mol at 1/7 ML. The estimated accuracy of measured heats is within 3 kJ/mol. Therefore, the standard enthalpy of formation of bidentate formate on Ni(111) is derived as −449.3 kJ/mol and the bond enthalpy to the Ni(111) surface is 319.6 kJ/mol. Comparison to our earlier results for Pt(111) shows that bidentate formate is 54 kJ/mol more stable on Ni(111). This is the first experimental measurement of the energy ofanymolecular fragment bonded toanyNi surface through metal-oxygen bonds, so it is an important benchmark for validating the accuracy of quantum mechanical calculations of a wide range of adsorbed oxygenates on Ni catalysts. Compared to previous density functional theory (DFT) calculations, we found that DFT calculations systematically underestimate the bond energy of formate to Ni(111), but correctly predict that it is stronger to Ni(111) than to Pt(111). The integral heat of HCOOH adsorption to make molecularly adsorbed formic acid was also measured and found to be 63.2 kJ/mol at 0.45 ML and 120–155 K.