Boosting the activity of transition metal carbides towards methane activation by nanostructuring

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Abstract
The interaction of methane with pristine surfaces of bulk MoC and Mo2C is known to be weak. In contrast, a series of X-ray photoelectron spectroscopy (XPS) experiments, combined with thermal desorption mass spectroscopy (TDS), for MoCy (y = 0.5–1.3) nanoparticles supported on Au(111)—which is completely inert towards CH4—show that these systems adsorb and dissociate CH4 at room temperature and low CH4 partial pressure. This industrially-relevant finding has been further investigated with accurate density functional theory (DFT) based calculations on a variety of MoCy supported model systems. The DFT calculations reveal that the MoCy/Au(111) systems can feature low C–H bond scission energy barriers, smaller than the CH4 adsorption energy. Our theoretical results for bulk surfaces of Mo2C and MoC show that a simple Brønsted–Evans–Polanyi (BEP) relationship holds for C–H bond scission on these systems. However, this is not the case for methane activation on the MoCy nanoparticles as a consequence of their unique electronic and chemical properties. The discovery that supported molybdenum carbide nanoparticles are able to activate methane at room temperature paves the road towards the design of a new family of active carbide catalysts for methane activation and valorisation, with important implications in climate change mitigation and carbon cycle closure.
Funding Information
  • Institució Catalana de Recerca i Estudis Avançats (2015 ICREA Academia Award)
  • Generalitat de Catalunya (2017SGR13, XRQTC)
  • Brookhaven National Laboratory (DE-SC0012704)
  • Ministerio de Economía y Competitividad (RYC-2012-10129)
  • Universitat de Barcelona (MICIUN RTI2018-095460-B-I00)

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