Carbonate Dimorphism, and the Reinterpretation of Rates of Lattice and Excess Oxygen-Driven Catalytic Cycles
Carbonate Dimorphism, and the Reinterpretation of Rates of Lattice and Excess Oxygen-Driven Catalytic Cycles
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DOI：
10.1016/j.jcat.2022.11.017
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发表时间：
2022-11
影响因子：
7.3
通讯作者：
Xiaohui Zhao;Qianyu Ning;L. Grabow;J. Rimer;Praveen Bollini
中科院分区：
文献类型：
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作者：
Xiaohui Zhao;Qianyu Ning;L. Grabow;J. Rimer;Praveen Bollini
局部偏离标称氧化物化学计量的催化意义仍然是至关重要的，但在散装氧化物介导的轻烷烃氧化反应的背景下，要阐明这一点仍然具有挑战性，部分原因是缺乏对表面活性氧位点计数的先验知识。碳酸盐二态性，即由于co2吸附在无负载的氧化镍表面而导致的碳酸盐形态的差异，可以用于量化晶格和过量氧的表面密度，并进一步消除它们各自对乙烷氧化反应网络中特定步骤的贡献。密度泛函理论、体积气体吸附、原位滴定、原位光谱和根据表面过量氧密度定量估计解释的瞬态动力学数据证实了过量氧参与了乙烷和O2产生乙烯的部分氧化循环。这些集体研究对与氧化镍介导的烷烃氧化有关的现场要求进行了更细致入微的解释。我们的研究结果表明，在反应条件下，多余的氧原子可以被滴定，并且这些位点（平均而言）比晶格氧对乙烯更具选择性。本文所使用的工具和方法将大量氧化物催化研究中看似不同的元素联系起来——一方面需要对氧化物表面非化学计量学进行定量估计；另一方面，无负载氧化物倾向于形成碳酸盐，并为探针分子结合特性的定量分析在商业相关的催化部分氧化反应系统中的活性位点密度和形态的阐明提供了一个模板。
Catalytic implications of local deviations from nominal oxide stoichiometry remain critical to consider yet challenging to elucidate in the context of bulk oxide-mediated light alkane oxidation reactions, in part due to a lack of a priori knowledge of surface active oxygen site counts. Carbonate dimorphism, i.e., differences in carbonate speciation resulting from CO2adsorption onto unsupported nickel oxide surfaces, can be exploited toward quantifying the surface density of lattice and excess oxygens, and to further deconvolute their respective contributions toward specific steps within the ethane oxidation reaction network. Density functional theory, volumetric gas sorption, in situ titration, in situ spectroscopy, and transient kinetic data interpreted in light of quantitative estimates of surface excess oxygen density confirm the involvement of excess oxygen in partial oxidative turnovers producing ethene from ethane and O2. These collective studies cast a more nuanced interpretation of site requirements pertaining to nickel oxide-mediated alkane oxidation. Our findings reveal that excess oxygen atoms can be titrated under reaction conditions, and that these sites are (on average) more selective to ethene than lattice oxygens. Tools and methodologies employed herein connect seemingly disparate elements of bulk oxide catalysis research – the need for quantitative estimates of oxide surface non-stoichiometry on the one hand, and the propensity of unsupported oxides toward carbonate formation on the other – and provide a template for the possible broader application of quantitative analyses of probe-molecule binding characteristics toward elucidation of active site density and speciation in catalytic partial oxidation reaction systems of commercial relevance.