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.

Hydrogenation of Pyridine and Hydrogenolysis of Piperidine overγ-Mo2N Catalyst: A DFT study

Increasing demands on producing environmentally friendly products are becoming a driving force for designing high active catalysts. Thus, surfaces that efficiently catalyse the nitrogen reduction reactions are vastly sought in moderating air-pollutant emissions. This contribution aims to computationally investigate the hydrodenitrogenation (HDN) networks of pyridine over γ-Mo2N(111) surface via density functional theory (DFT) approach. Various adsorption configurations have been considered for the molecularly adsorbed pyridine. Findings indicate that pyridine can be adsorbed via side-on and end-on modes in six geometries in which one adsorption site is revealed to have the lowest adsorption energy of (-45.3 kcal/mol(. Over nitrogen hollow site adsorption site, initial HDN steps proceed by the stepwise hydrogenation of pyridine into piperidine followed the Langmuir−Hinshelwood mechanism. The obtained findings are the first to theoretically model the hydrogenation pathways of pyridine to form piperidine then the hydrogenolysis of piperidine producing C5H12 and NH3 over metal nitride and paved the way for further investigations to better understanding such an important nitrogen removal reactions.