Transition metal nitride catalysts for selective conversion of oxygen-containing molecules.

Earth abundant transition metal nitrides (TMNs) are a promising group of catalysts for a wide range of thermocatalytic, electrocatalytic and photocatalytic reactions, with potential to achieve high activity and selectivity while reducing reliance on the use of Pt-group metals. However, current fundamental understanding of the active sites of these materials and the mechanisms by which selective transformations occur is somewhat lacking. Recent investigations of these materials from our group and others have utilized probe molecules, model surfaces, and in situ techniques to elucidate the origin of their activity, strong metal-support interactions, and unique d-band electronic structures. This Perspective discusses three classes of reactions for which TMNs have been used as case studies to highlight how these properties, along with synergistic interactions with metal overlayers, can be exploited to design active, selective and stable TMN catalysts. First, studies of the reactions of C1 molecules will be discussed, specifically highlighting the ability of TMNs to activate CO2. Second, the upgrading of biomass and biomass-derived oxygenates over TMN catalysts will be reviewed. Third, the use of TMNs for H2 production via water electrolysis will be discussed. Finally, we will discuss the challenges and future directions in the study of TMN catalysts, in particular expanding on opportunities to enhance fundamental mechanistic understanding using model surfaces, the elucidation of active centers via in situ techniques, and the development of efficient synthesis methods and design principles.

Glycerol Electrooxidation over Precision-Synthesized Gold Nanocrystals with Different Surface Facets.

Electrochemical glycerol oxidation (EGO) emerges as a promising route to valorize glycerol, an underutilized byproduct from biodiesel production, into value-added chemicals. This study employed three types of gold (Au) nanocrystals with controlled shapes to elucidate the facet-dependent electrocatalytic behavior in EGO. Octahedral, rhombic dodecahedral, and cubic Au nanocrystals with {111}, {110}, and {100} facets, respectively, were precisely synthesized with uniform size and shape. Rhombic dodecahedra exhibited the lowest onset potential for EGO due to facile AuOH formation, while octahedra showed enhanced electrochemical activity for glycerol oxidation and resistance to poisoning. In-situ FTIR analysis revealed that Au {111} surfaces selectively favored C2 products, whereas Au {100} surfaces promoted C3 product formation, highlighting the significant effect of facet orientation on EGO performance and informing catalyst design.