PraMixCat · Operando studies of praseodymium based mixed oxide supported metal catalysts for the direct conversion of methane to methanol: bridge the gap of model catalysis and ambient applications

The direct conversion of methane to methanol (DCMM) has attracted strong interest due to its great potential use in the energy and chemicals sectors, at the same time diminishing the greenhouse effect. However, this process is challenging for heterogeneous catalysis due to the high energy required for cleaving the C−H bond in CH4, as wells as the facile over-oxidation of CH3OH to CO or CO2. Recent ultrahigh vacuum (UHV) studies indicate that metal-oxide surfaces/interfaces can facilitate DCMM with high selectivity at low temperature in a single batch mode. Inspired by the model studies, in this project we will synthesize a series of praseodymium mixed oxides supported Cu and Au catalysts (i.e. Cu-Au/Ce1-xPrxO2-δ, Cu-Au/Zr1-xPrxO2-δ) and explore its application for DCMM under ambient conditions. Major challenges in designing this system for DCMM is the identification of the active sites in the working state and correspondingly tailoring its properties, which can be overcome by using in situ/operando techniques and ‘defect engineering’. The catalytic performance will be investigated using both a batch (and flow) reactor and an operando spectroscopy cell. Near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) and X-ray absorption near edge structure spectroscopy (XANES) will be used to determine the electronic state of the metals. Structure, including defects, of catalysts will be investigated by in situ X-ray absorption spectroscopy (XAS), X-ray diffraction (XRD), Selected Area Electron Diffraction (SAED) and Raman scattering. The reaction mechanism will be investigated by concentration-modulation Fourier transform infrared (FTIR) spectroscopy and operando Raman scattering. This study will provide strongly validated mechanistic and structural conclusions for the future design and optimization of nanostructured DCMM catalysts and represent ground-breaking work at the intersection of surface science and applied catalysis.