Chen Pak Wing, Maiti Debtanu, Liu Ru-Fen, Grabow Lars C, Harold Michael P
William A Brookshire Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States.
CDTi Advanced Materials, Inc., 1641 Fiske Place, Oxnard, California 93033, United States.
ACS Eng Au. 2023 Dec 23;4(2):193-203. doi: 10.1021/acsengineeringau.3c00053. eCollection 2024 Apr 17.
A combined experimental and molecular modeling study identifies a family of spinel oxides that in combination with PGM (platinum group metals) provide enhanced methane oxidation activity. With a reduction in greenhouse gas (GHG) emissions urgently needed, there is renewed interest in the use of natural gas vehicles (NGVs) and engines (NGEs) for transportation, commerce, and industrial applications. NGVs and NGEs emit less CO than their petroleum-derived counterparts but may emit uncombusted methane, an even more potent GHG. For stoichiometric engines, methane oxidation catalysts containing PGM and spinel oxide in layered architectures offer increased methane oxidation activity and lower light-off temperatures (). The reducible spinel oxide has direct and indirect roles that are effectively described by the bulk oxygen vacancy formation energy (). We apply density functional theory (DFT) to identify several earth-abundant, cobalt-rich spinel oxides with favorable , shown to correlate with dynamic oxygen storage capacity (DOSC) and CO and H oxidation activity. We experimentally rank-order the DFT-identified spinel oxides in combination with Pt+Pd for their methane oxidation activity measurements, under both time-invariant and modulated feed conditions. We show good agreement between the activity and the DFT-computed reducibility of the spinel oxide. The findings suggest spinel reducibility is a key factor in achieving enhanced low-temperature methane conversion, enabled through a balance of methane activation on the PGM sites and subsequent oxidation of the intermediates and byproducts on spinel oxides. In agreement with its computationally predicted , NiCoO was confirmed to have the highest DOSC and lowest among the tested spinel samples.
一项结合实验和分子模拟的研究确定了一类尖晶石氧化物，它们与铂族金属（PGM）结合可提高甲烷氧化活性。由于迫切需要减少温室气体（GHG）排放，人们对将天然气车辆（NGV）和发动机（NGE）用于运输、商业和工业应用重新产生了兴趣。NGV和NGE的一氧化碳排放量低于以石油为原料的同类产品，但可能会排放未燃烧的甲烷，这是一种更强效的温室气体。对于化学计量发动机，层状结构中含有PGM和尖晶石氧化物的甲烷氧化催化剂具有更高的甲烷氧化活性和更低的起燃温度。可还原的尖晶石氧化物具有直接和间接作用，可用体相氧空位形成能有效描述。我们应用密度泛函理论（DFT）来确定几种储量丰富、富含钴的尖晶石氧化物，其具有良好的[具体参数]，已证明与动态储氧能力（DOSC）以及一氧化碳和氢气氧化活性相关。我们通过实验对DFT确定的尖晶石氧化物与铂加钯结合进行甲烷氧化活性测量进行排序，测量条件包括时间不变和调制进料条件。我们发现尖晶石氧化物的活性与DFT计算的可还原性之间具有良好的一致性。研究结果表明，尖晶石的可还原性是实现低温甲烷转化增强的关键因素，这是通过PGM位点上甲烷活化与尖晶石氧化物上中间体和副产物的后续氧化之间的平衡实现的。与计算预测结果一致，在测试的尖晶石样品中，NiCoO被证实具有最高的DOSC和最低的[具体参数]。
