Institute for Physical Chemistry, University of Göttingen, Tammannstraße 6, 37077 Göttingen, Germany.
Department of Dynamics at Surfaces, Max Planck Institute for Multidisciplinary Sciences, am Faßberg 11, 37077 Göttingen, Germany.
Science. 2022 Jul 22;377(6604):394-398. doi: 10.1126/science.abq1414. Epub 2022 Jul 21.
There is wide interest in developing accurate theories for predicting rates of chemical reactions that occur at metal surfaces, especially for applications in industrial catalysis. Conventional methods contain many approximations that lack experimental validation. In practice, there are few reactions where sufficiently accurate experimental data exist to even allow meaningful comparisons to theory. Here, we present experimentally derived thermal rate constants for hydrogen atom recombination on platinum single-crystal surfaces, which are accurate enough to test established theoretical approximations. A quantum rate model is also presented, making possible a direct evaluation of the accuracy of commonly used approximations to adsorbate entropy. We find that neglecting the wave nature of adsorbed hydrogen atoms and their electronic spin degeneracy leads to a 10× to 1000× overestimation of the rate constant for temperatures relevant to heterogeneous catalysis. These quantum effects are also found to be important for nanoparticle catalysts.
人们对开发能够准确预测金属表面化学反应速率的理论有着广泛的兴趣，特别是在工业催化应用中。传统方法包含许多缺乏实验验证的近似。实际上，很少有反应存在足够准确的实验数据，甚至无法与理论进行有意义的比较。在这里，我们提出了在铂单晶表面上氢原子复合的实验导出的热速率常数，这些速率常数足够准确，可以对已建立的理论近似进行测试。我们还提出了一个量子速率模型，使得可以直接评估常用吸附物熵近似的准确性。我们发现，忽略吸附氢原子的波动性及其电子自旋简并性会导致与多相催化相关的温度下速率常数高估 10 到 1000 倍。这些量子效应对于纳米粒子催化剂也很重要。
