Recent Advances in Carbon Dioxide Adsorption, Activation and Hydrogenation to Methanol using Transition Metal Carbides

Abstract

The inevitable emission of carbon dioxide (CO 2 ) due to the burning of a substantial amount of fossil fuels has led to serious energy and environmental challenges. Metal-based catalytic CO 2 transformations into commodity chemicals are a favorable approach in the CO 2 mitigation strategy. Among these transformations, selective hydrogenation of CO 2 to methanol is the most promising process that not only fulfils the energy demands but also re-balances the carbon cycle. The investigation of CO 2 adsorption on the surface of heterogeneous catalyst is highly important because the formation of various intermediates which determines the selectivity of product. Transition metal carbides (TMCs) have received considerable attention in recent years because of their noble metal-like reactivity, ceramic-like properties, high chemical and thermal stability. These features make them excellent catalytic materials for a variety of transformations such as CO 2 adsorption and its conversion into value-added chemicals. Herein, the catalytic properties of TMCs are summarize along with synthetic methods, CO 2 binding modes, mechanistic studies, effects of dopant on CO 2 adsorption, and carbon/metal ratio in the CO 2 hydrogenation reaction to methanol using computational as well as experimental studies. Additionally, this Review provides an outline of the challenges and opportunities for the development of potential TMCs in CO 2 hydrogenation reactions.

Transition Metal Carbides: Emerging CO2 Hydrogenation Catalysts, from Recent Advance to Future Exploration

“…They also stated that the adsorbed MMC configuration is more active and susceptible to hydrogenation processes. [22] Chen et al explored the mechanism of CO 2 activation on TMCs through theoretical calculations and concluded that the binding energy of TMCs with O (OBE) played a considerable role in CO 2 hydrogenations. [25] When TMCs had a high OBE value, CO 2 molecules were prone to be directly dissociated to generate CO (*CO 2 →*CO+*O).…”

“… 1)TMCs are electrophilic, so they exhibit unique adsorption capacity and catalytic performance for molecules with weak oxidation properties. [ 7f,22–24 ] In particular, the adsorption strength of TMCs for CO 2 is neither too strong nor too weak because of the unique atomic arrangement between C and their parent metals. According to the Sabatier principle, TMCs could exhibit better potential as ideal and powerful CO 2 hydrogenation catalysts because of the appropriate CO 2 activation ability than metals and metal oxides.…”

Consecutive Reduction of Five Carbon Dioxide Molecules by Gas-Phase Niobium Carbide Cluster Anions Nb3C4–: Unusual Mechanism for Enhanced Reactivity by the Carbon Ligands

“…The conversion of CO 2 into value-added chemicals may be a crucial approach to mitigate climate change and reduce reliance on fossil fuels. 1 Several reactions, such as the reverse water gas shift (CO 2 + H 2 → CO + H 2 O), dry reforming of methane (CO 2 + CH 4 → 2CO + 2H 2 ), and selective hydrogenation (CO 2 + 3H 2 → CH 3 OH + H 2 O), have been extensively investigated. 2,3 To this end, noble metals and copper-based catalysts are required due to the thermodynamic stability and kinetic inertness of CO 2 molecules, while noble metals are of high cost, and copper-based catalysts are easily deactivated at high temperatures.…”

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

“…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. ,,, …”