Cobalt Oxide Model Catalysis Across the Materials and Pressure Gap (COMCAT)

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Cobalt oxide has recently turned out to be a novel, highly active heterogeneous catalyst for key processes in future energy and environmental technology. This includes e.g. low-temperature CO oxidation, the related PROX reaction (preferential oxidation of CO in excess H2), the total oxidation of VOCs (volatile organic compounds), and the reforming of hydrocarbon oxygenates for hydrogen production. Most importantly, cobaltoxide- based catalysts hold a unique potential for replacing or reducing the demand for critical materials (noble metals and rare earth oxides). Despite these outstanding prospects, the origin of the surprising cobalt oxide surface chemistry has remained a mystery up to date. Neither the extreme dependence of activity on surface structure nor the mechanisms by which metal (e.g. Pd) and oxide (e.g. CeO2) modifiers enhance stability and activity are truly understood. The aim of this joint project is to acquire an understanding of the catalytic activity of cobalt oxide materials at the molecular level. Towards this aim the project partners bring together the complementary expertise for a state-of-the-art model catalysis (surface science) approach: (A) the atomic-level structural characterization of reactive sites on complex model catalysts, (B) mechanistic and microkinetic studies of catalytic reactions under UHV conditions, and (C) transfer of this knowledge to realistic reaction conditions by in-situ spectroscopy up to realistic ambient pressure conditions. We will take advantage of the leading expertise of one project partner in preparation of ordered cobalt oxide films, providing access to a unique library of bulk and surfaces structures. We will probe adsorption and reaction on these surface structures, characterize relevant defects at the atomic scale with respect to their geometric and electronic properties, and subsequently modify these structures by metal (Pd) and oxide (CeO2) cocatalysts. In this project, we will mainly focus on low-temperature CO-oxidation and PROX, but perform first explorative work towards oxidation and reforming reactions. Simultaneously, we will cross the materials gap and the pressure gap for cobalt oxide catalysts for the first time and, finally, link the obtained knowledge to industrial-grade powder catalysts by in-situ spectroscopy from UHV to realistic reaction conditions. The interdisciplinary approach of this project will allow us to identify structure-functionality relationships of catalytic processes at an unprecedented level of detail and will guide rational strategies towards future development of complex multifunctional cobalt oxide catalysts.