Structural tuning and catalysis of tungsten carbides for the regioselective cleavage of C O bonds

Role of defects in carbon materials during metal-free formic acid dehydrogenation

“…49 All the calculations include the long-range dispersion correction approach by Grimme, 50,51 which is an improvement on pure DFT to evaluate molecular interactions. [52][53][54][55] We included also the implicit solvation model as implemented in VASPsol describing the bulk water effect of electrostatics, cavitation, and dispersion on the FA interaction with the C-materials. 56,57 The optimization thresholds were 10 −5 eV and 0.01 eV/Å for electronic and ionic forces relaxation, respectively.…”

Advances in Sustainable Catalysis: A Computational Perspective

“…However, not all DFT functionals are created equally and at the turn of the millennium John Perdew proposed a climbing scale coined the “Jacob's ladder” with pure GGA functional near the bottom and hybrid functionals close to the top (Perdew and Schmidt, 2001; Sousa et al, 2007). In practice, this often means that in silico homogenous catalytic systems, which are often modeled with hybrid functionals (Green et al, 2014; Wójcik et al, 2016; Wojdyła and Borowski, 2016; Delarmelina et al, 2017; Dabral et al, 2018), produce results that are closer to experimental values then those obtained when modeling heterogenous catalysts, where pure GGA are frequently the only efficient functionals to be implemented periodically (Hammond et al, 2012; Zhao et al, 2015; Ishikawa et al, 2017; Kunkel et al, 2018; Morales-Gar et al, 2018; Fang et al, 2019; Wang et al, 2019). Unfortunately, there is no universal functional and the most appropriate exchange–correlation term must be assessed on a system specific basis by benchmarking theoretically obtained electronic or catalytic properties to those observed experimentally (Laurent and Jacquemin, 2013; de Visser et al, 2014; Hickey and Rowley, 2014; Cantú Reinhard et al, 2016); additionally, the amount of Hartree–Fock component included in the exchange component of the most commonly used hybrid functionals can be modified to produce a better match between experimental and in silico values (Reiher et al, 2001; Walker et al, 2013).…”

Stable and Antisintering Tungsten Carbides with Controllable Active Phase for Selective Cleavage of Aryl Ether C–O Bonds

“…The WxC/CNT-CTR based on the carbothermal reduction was prepared at 900-950 °C for 2-6 h under Ar flow. For comparison, the C-supported tungsten carbide derived from RF polymer was prepared by carburization of organic-inorganic hybrid precursor according our previous reports, 8,29 denoted as WxC@CS(RF). The samples with CNTs incorporation were synthesized by similar methods by adding CNTs and other C materials during the preparation of precursors, denoted as WxC@CS(RF)-CNTs.…”

“…W2C, WC, Mo2C and MoC) towards different catalytic behaviors, preventing the wide application of these cost-efficient materials. 8,9 The most prevailing approach for carbide synthesis is temperature-programmed-reduction (TPR) under gaseous carbon precursors such as CH4, CO and C3H8. [10][11][12] Unfortunately, the rapid diffusion of carbon through the gas-solid interface is barely suspended, resulting in uncontrollable phases and coke deposition (Scheme 1a).…”

“…activated carbon, carbon nanotube, carbon nanofiber), polymers and metal-organic Frameworks (MOFs), which aims to improve the quality of as-built TMCs. 7,8,[14][15][16][17][18][19] However, the high carburizing temperature to overcome the thermodynamic and kinetic barriers for carbon insertion always induces unexpecting support degradation and particle sintering (Scheme 1b). The method is also limited to the support choices, uncontrollable phase compositions, small metal-carbon interfaces, and difficulty in controlling particle sizes.…”