Ding Zhao-Bin, Maestri Matteo
Laboratory of Catalysis and Catalytic Processes-Dipartimento di Energia, Politecnico di Milano, via La Masa 34, Milano 20156, Italy.
Ind Eng Chem Res. 2019 Jun 12;58(23):9864-9874. doi: 10.1021/acs.iecr.9b01628. Epub 2019 Jun 4.
We propose and assess a criterion for the application of Brønsted-Evans-Polanyi (BEP) relations for dissociation reactions at surfaces. A theory-to-theory comparison with density functional theory calculations is presented on different reactions, metal catalysts, and surface terminations. In particular, the activation energies of CH, CO, and -COOH dissociation reactions on (100), (110), (111), and (211) surfaces of Ni, Cu, Rh, Pd, Ag, and Pt are considered. We show that both the activation energy and the reaction energy can be decomposed into two contributions that reflect the influence of reactant and products in determining either the activation energy or the reaction energy. We show that the applicability of the BEP relation implies that the reaction energy and activation energy correlate to these two contributions in the range of conditions to be described by the BEP relation. A lack of correlation between these components for the activation energy is related to a change in the character of the transition state (TS) and this turns out to be incompatible with a BEP relation because it results in a change of the slope of the BEP relation. Our analysis reveals that these two contributions follow the same trends for the activation energy and for the reaction energy when the path is not characterized either by the formation of stable intermediates or by the change of the binding mechanism of the reactant. As such, one can assess whether a BEP relation can be applied or not for a set of conditions only by means of thermochemical calculations and without requiring the identification of the TS along the reaction pathway. We provide evidence that this criterion can be successfully applied for the preliminary discrimination of the applicability of the BEP relations. For instance, on the one hand, our analysis provides evidence that the two contributions are fully anticorrelated for the -COOH dissociation reactions on different metals and surfaces, thus revealing that the reaction is characterized by a change in the TS character. In this situation, no BEP relation can be used to describe the activation energy trend among the different metals and surfaces in full agreement with our DFT calculations. On the other hand, our criterion reveals that the TS character is not expected to change for CH dissociation reactions both for the same facet, different metals and for same metal, different facets, in good agreement with the DFT calculations of the activation energy. The formation of multiple stable intermediates along the reaction pathways and the change of the binding mechanism of one of the reactants are demonstrated to affect the validity of the criterion. As a whole, our findings make possible an assessment of the applicability of the BEP relation and paves the way toward its use for the exploration of complex reaction networks for different metals and surfaces.
我们提出并评估了一种用于表面解离反应的布朗斯特-埃文斯-波拉尼（BEP）关系应用的判据。针对不同反应、金属催化剂和表面终止情况，给出了与密度泛函理论计算的理论间比较。特别地，考虑了Ni、Cu、Rh、Pd、Ag和Pt的（100）、（110）、（111）和（211）表面上CH、CO和 -COOH解离反应的活化能。我们表明，活化能和反应能都可分解为反映反应物和产物在决定活化能或反应能时影响的两种贡献。我们表明，BEP关系的适用性意味着在BEP关系所描述的条件范围内，反应能和活化能与这两种贡献相关。活化能的这些组分之间缺乏相关性与过渡态（TS）性质的变化有关，而这与BEP关系不相容，因为它导致BEP关系斜率的变化。我们的分析表明，当反应路径既不以稳定中间体的形成为特征，也不以反应物结合机制的变化为特征时，这两种贡献对于活化能和反应能遵循相同趋势。因此，仅通过热化学计算，无需确定反应路径上的TS，就可以评估一组条件下BEP关系是否适用。我们提供的证据表明，该判据可成功用于初步判别BEP关系的适用性。例如，一方面，我们的分析表明，对于不同金属和表面上的 -COOH解离反应，这两种贡献完全反相关，从而表明该反应以TS性质的变化为特征。在这种情况下，与我们的密度泛函理论计算完全一致，无法用BEP关系描述不同金属和表面之间的活化能趋势。另一方面，我们的判据表明，对于相同晶面、不同金属以及相同金属、不同晶面的CH解离反应，TS性质预计不会改变，这与活化能的密度泛函理论计算结果吻合良好。沿反应路径形成多个稳定中间体以及其中一种反应物结合机制的变化被证明会影响该判据的有效性。总体而言，我们的研究结果使得能够评估BEP关系的适用性，并为其用于探索不同金属和表面的复杂反应网络铺平了道路。
