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 CO₂ adsorption 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.

与标称氧化物化学计量的局部偏差的催化影响仍然是考虑的关键，但在大量氧化物介导的轻质烷烃氧化反应的背景下难以阐明，部分原因是缺乏表面活性氧位点计数的先验知识。碳酸盐二态性，即由 CO _{2引起的碳酸盐形态差异}吸附到无支撑的氧化镍表面上，可用于量化晶格和过量氧的表面密度，并进一步解卷积它们各自对乙烷氧化反应网络中特定步骤的贡献。根据表面过量氧密度的定量估计解释的密度泛函理论、体积气体吸附、原位滴定、原位光谱和瞬态动力学数据证实，过量氧气参与了从乙烷和 O _{2生产乙烯的部分氧化转换}. 这些集体研究对与氧化镍介导的烷烃氧化有关的场地要求做出了更细致的解释。我们的研究结果表明，过量的氧原子可以在反应条件下滴定，并且这些位点（平均而言）比晶格氧对乙烯更具选择性。本文使用的工具和方法将本体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进行定量估计，另一方面需要无负载氧化物形成碳酸盐——并为探针分子结合特性的定量分析可能更广泛地应用于阐明商业相关的催化部分氧化反应系统中的活性位点密度和物种形成。