Effects of Co-adsorbed Water on Different Bond Cleavages of Oxygenates on Pd (111)
Effects of Co-adsorbed Water on Different Bond Cleavages of Oxygenates on Pd (111)
复制标题
DOI：
10.1021/acscatal.1c03764
复制
发表时间：
2021-12-28
期刊：
影响因子：
12.9
通讯作者：
Arnadottir, Liney
中科院分区：
文献类型：
--
作者：
Chukwu, Kingsley C.;Arnadottir, Liney
实验研究表明，共吸附物和溶剂影响多相催化剂的活性和选择性，但它们如何影响不同的键断裂和平行反应的网络还没有很好的理解。在这里，我们提出了一个密度泛函理论（DFT）计算共吸附水如何影响不同的键断裂的含氧化合物在金属表面上，使用乙酸的分解在Pd（111）作为模型系统的含氧化合物，在生物质转化的应用。共吸附水的存在通常增强O-H键裂解，同时通常抑制OC-O、C-C和OC-OH键裂解。共吸附水对C-H键断裂的影响变化最大，并且取决于过渡态的性质以及共吸附水如何稳定初始和最终状态。虽然这些趋势作为一般指导是有用的，但它们不足以预测对复杂反应网络的影响，例如具有几个平行反应路径的乙酸分解。在不存在共吸附水的情况下，两个最低能量的途径是通过共同的CH 2COO中间体的脱羧和脱羰基途径。但是，通过抑制OC-O键裂解但增强CH 2COO的C-C键裂解，在水存在下CC抑制的一般趋势的三个例外之一，两个最低自由能途径是在水存在下脱羧形成CO2。这说明了单个反应步骤如何影响具有许多平行的、能量相似路径的复杂反应网络。这表明，共吸附水的存在使得乙酸脱羧（形成二氧化碳）比乙酸脱羰基（形成一氧化碳）在Pd（111）上更有利。
Experimental studies have shown that co-adsorbates and solvents affect both the activity and selectivity of heterogeneous catalysts, but how they affect different bond cleavages and a network of parallel reactions is not well understood. Here we present a density functional theory (DFT) calculation of how co-adsorbed water affects different bond cleavages of oxygenates on metal surface, using decomposition of acetic acid over Pd (111) as a model system for oxygenates, with application in biomass conversion. The presence of co-adsorbed water generally enhances O-H bond cleavage while generally inhibiting the OC-O, C-C, and OC-OH bond cleavage. The influence of co-adsorbed water on C-H bond cleavage varies the most and depends on the nature of the transition state and how co-adsorbed water stabilizes the initial and final state. Although these trends are useful as general guidance, they are not sufficient to predict the effect on a complex reaction network such as acetic acid decomposition that has several parallel reaction paths. In the absence of co-adsorbed water, the two lowest energy pathways are decarboxylation and decarbonylation pathways through a common CH2COO intermediate. But through an inhibition of OC-O bond cleavage but enhancement of C-C bond cleavage of CH2COO, one of three exceptions to the general trend of CC inhibition in the presence of water, the two lowest free energy pathways are decarboxylation forming CO2 in the presence of water. This illustrates how a single reaction step can affect a complex reaction network with many parallel, energetically similar paths. This suggests that the presence of co-adsorbed water makes acetic acid decarboxylation (formation of carbon dioxide) more favorable than acetic acid decarbonylation (formation of carbon monoxide) over Pd (111).