Prats Hèctor, Gutiérrez Ramón A, Piñero Juan José, Viñes Francesc, Bromley Stefan T, Ramírez Pedro J, Rodriguez José A, Illas Francesc
Departament de Ciència de Materials i Química Física & Institut de Quı́mica Teòrica i Computacional (IQTCUB) , de la Universitat de Barcelona , Martí i Franquès 1-11 , 08028 Barcelona , Spain.
Chemistry Department , Brookhaven National Laboratory , Upton , New York 11973 , United States.
J Am Chem Soc. 2019 Apr 3;141(13):5303-5313. doi: 10.1021/jacs.8b13552. Epub 2019 Mar 18.
Methane is an extremely stable molecule, a major component of natural gas, and also one of the most potent greenhouse gases contributing to global warming. Consequently, the capture and activation of methane is a challenging and intensively studied topic. A major research goal is to find systems that can activate methane, even at low temperatures. Here, combining ultrahigh vacuum catalytic experiments, X-ray photoemission spectra, and accurate density functional theory (DFT) based calculations, we show that small Ni clusters dispersed on the (001) surface of TiC are able to capture and dissociate methane at room temperature. Our DFT calculations reveal that two-dimensional Ni clusters are responsible for this chemical transformation, confirming that the lability of the supported clusters appears to be a critical aspect in the strong adsorption of methane. A small energy barrier of 0.18 eV is predicted for CH dissociation into adsorbed methyl and atomic hydrogen species. In addition, the calculated reaction free energy profile at 300 K and 1 atm of CH shows no effective energy barriers in the system. Comparison with other reported systems which activate methane at room temperature, including oxide and zeolite-based materials, indicates that a different chemistry takes place on our metal/carbide system. The discovery of a carbide-based surface able to activate methane at low temperatures paves the road for the design of new types of catalysts which can efficiently convert this hydrocarbon into other added-value chemicals, with implications in climate change mitigation.
甲烷是一种极其稳定的分子,是天然气的主要成分,也是导致全球变暖的最具影响力的温室气体之一。因此,甲烷的捕获和活化是一个具有挑战性且受到广泛研究的课题。一个主要的研究目标是找到即使在低温下也能活化甲烷的体系。在此,通过结合超高真空催化实验、X射线光电子能谱以及基于精确密度泛函理论(DFT)的计算,我们表明分散在TiC(001)表面的小尺寸镍簇能够在室温下捕获并解离甲烷。我们的DFT计算表明二维镍簇是这种化学转化的原因,证实了负载簇的活性似乎是甲烷强吸附的一个关键因素。预测CH解离为吸附的甲基和氢原子物种的能垒为0.18 eV。此外,在300 K和1 atm下计算的CH反应自由能曲线表明该体系中不存在有效的能垒。与其他报道的在室温下活化甲烷的体系(包括氧化物和沸石基材料)相比,表明我们的金属/碳化物体系发生了不同的化学反应。发现一种能够在低温下活化甲烷的碳化物基表面为设计新型催化剂铺平了道路,这种催化剂能够有效地将这种碳氢化合物转化为其他高附加值化学品,对缓解气候变化具有重要意义。