Effective and Highly Selective CO Generation from CO₂ Using a Polycrystalline α-Mo₂C Catalyst

Present experiments show that synthesized polycrystalline hexagonal α-Mo 2 C is a highly efficient and selective catalyst for CO 2 uptake and conversion to CO through the reverse water gas shift reaction. The CO 2 conversion is ∼16% at 673 K, with selectivity toward CO > 99%. CO 2 and CO adsorption is monitored by DRIFTS, TPD, and microcalorimetry, and a series of DFT based calculations including the contribution of dispersion terms. The DFT calculations on most stable model surfaces allow for identifying numerous binding sites present on the catalyst surface, leading to a high complexity in measured and interpreted IR- and TPD-spectra. The computational results also explain ambient temperature CO 2 dissociation toward CO as resulting from the presence of surface facets such as Mo 2 C(201)-Mo/C—displaying Mo and C surface atoms—and Mo-terminated Mo 2 C(001)-Mo. An ab initio thermodynamics consideration of reaction conditions, however, demonstrates that these facets bind CO 2 and CO + O intermediates too strongly for a subsequent removal, whereas the Mo 2 C(101)-Mo/C exhibits balanced binding properties, serving as a possible explanation of the observed reactivity. In summary, results show that polycrystalline α-Mo 2 C is an economically viable, highly efficient, and selective catalyst for CO generation using CO 2 as a feedstock.