Role and dynamics of transition metal carbides in methane coupling

Abstract

Transition metal carbides have numerous applications and are known to excel in terms of hardness, thermal stability and conductivity. In particular, the Pt-like behavior of Mo and W carbides has...

C1 Chemistry on Metal Carbide Nanoparticles: Boosting the Conversion of CO2 and CH4

“…The dominant product was methane. A result in agreement with the trends seen for CO 2 hydrogenation on powders of Mo 2 C. ,,,, …”

“…The dominant product was methane. A result in agreement with the trends seen for CO 2 hydrogenation on powders of Mo 2 C. 13,20,21,24,83 A drastic change is seen in the surface chemistry when moving to MoC or other 1:1 metal-to-carbon systems that adopt a rocksalt structure. [25][26][27]83 On these 1:1 compounds, the CO 2 molecules did not dissociate spontaneously as seen on β-Mo 2 C(001).…”

“…Carbon dioxide (CO 2 ) and methane (CH 4 ) are among the worst greenhouse gases and main contributors to global warming and climate change. − Both molecules are highly stable, are nonpolar, and display a low reactivity. − New initiatives emphasize the need to design and optimize processes for the trapping, storage, and conversion of CO 2 and CH 4 . − These processes involve three essential components: (1) A reactive center that binds and activates the CO 2 or CH 4 molecule, (2) a surrounding phase with reactants or solvents, and (3) a source of thermal, electrical, or photochemical energy. − Catalytic conversion of CO 2 or CH 4 to chemicals and fuels is a “two birds, one stone” approach toward solving the climate change problem and energy demand-supply deficit in the modern world. − Conversion to oxygenates or light alkanes are promising processes for a large scale utilization of CO 2 and CH 4 . − These conversions are hampered by challenges associated with the low activity and selectivity of currently used catalysts. In recent years, transition metal carbides (TMCs) have emerged as useful materials for the activation and transformation of CO 2 and CH 4 . − …”

“…Since the pioneering work of Levy and Boudart, where the hydrogenation ability of TMCs was described as comparable to that of Pt-group elements, these materials have been the focus of many studies in catalysis. − ,− Transition metal carbides can display a unique combination of the physical properties characteristic of noble metals and ceramics. , Many TMCs are good electrical and thermal conductors while possessing ultrahardness and very high melting points. , The degree of ionicity in a metal–carbon bond is much smaller than in a metal-oxide bond, opening the possibility for different catalytic properties. , In a metal carbide, metal and carbon centers can participate in the binding an activation or CO 2 or CH 4 . ,,− The formation of C–C or CC bonds can occur after adsorbing CO 2 or CH x fragments on a metal carbide. ,− The carbon/metal ratio is an important variable that can be used to tune the breaking of one or two hydrogen bonds in the CO 2 molecule and favor the selectivity during hydrogenation toward oxygenates or alkanes. ,− For a given carbon/metal ratio, different catalytic properties have been seen for bulk, two-dimensional (2D) and nanostructure systems. ,,, Furthermore, transition metal carbide surfaces can act as supports, having an useful ability to modify the catalytic properties of supported metals not seen in the case of metal oxide substrates. ,,, …”

Modulation of Rotational Dynamics in Halogen-Bonded Cocrystalline Solids

“…Molecular dynamics are crucial to the functionality of biomolecules, chemical catalysts, , and supramolecular systems . The intelligent and deliberate engineering of molecular structure and dynamics also holds the key to improving the properties of designer proteins, advanced functional materials, and molecular machines. , While atomic-level structure resolution has long been a goal of chemical and biochemical crystallography, be it via diffraction methods, complementary approaches such as NMR crystallography, , or purely computational crystal structure prediction (CSP) methods, it has become more evident in recent years that static structures only provide part of the story and that dynamical features are of comparable importance in many cases. , …”