Highly Dispersed Molybdenum Oxycarbide Clusters Supported on Multilayer Graphene for the Selective Reduction of Carbon Dioxide.

Molybdenum oxycarbide clusters are novel nanomaterials that exhibit attractive catalytic activity; however, the methods for their production are currently very restrictive. This work represents a new strategy for the creation of near-subnanometer size molybdenum oxycarbide clusters on multilayer graphene. To adsorb Mo-based polyoxometalates of the type [PMo12 O40 ]3- as a precursor for Mo oxycarbide clusters, the novel tripodal-phenyl cation N,N,N-tri(4-phenylbutyl)-N-methylammonium ([TPBMA]+ ) is synthesized. [TPBMA]+ exhibits superior adsorption on multilayer graphene compared to commercially available cations such as tetrabutylammonium ([nBu4 N]+ ) and tetraphenylphosphonium ([PPh4 ]+ ). Using [TPBMA]+ as an anchor, highly dispersed precursor clusters (diameter: 1.0 ± 0.2 nm) supported on multilayer graphene are obtained, as confirmed by high-resolution scanning transmission electron microscopy. Remarkably, this new material achieves the catalytic reduction of CO2 to selectively produce CO (≈99.9%) via the reverse water-gas-shift reaction, by applying carbothermal hydrogen reduction to generate Mo oxycarbide clusters in situ.