CO oxidation catalyzed by silicon carbide (SiC) monolayer: A theoretical study

Unveiling the effect of 2D silagraphene structural diversity on electronic properties: DFT, DOS, and ELF studies

Recently, fully π-functional two-dimensional (2D) materials have been reported for electronic device applications. Graphene is one of these 2D materials that is attributed to 2D electron confinement effects and exhibits an aromatic character; however, it is characterized by vanishing the bandgap energy. Hence, research was focused on the discovery of graphene-based 2D materials to reduce the bandgap energy. Herein, we investigate the silagraphene structures (Si_xC_y) using DFT calculations to undertake and improve structural, physico-chemical, and electronic properties. Various types of 2D networks have been investigated by considering C-C and C-Si bonds in relative positions. Both conjugation and hyperconjugation phenomenon have been deeply examined and it seemed that they take advantage of each other depending on the C-C and C-Si bond positions. Localized orbital locator (LOL) and electron localization function (ELF) were also performed to examine the electronic densities in the investigated 2D networks and unveil the electronic properties of the studied materials.

Al-Embedded C2N: a DFT study on a promising catalyst for CO oxidation

Al-C2N catalyst exhibits efficient catalytic performance for CO oxidation.

Porous Silicon Carbide (SiC): A Chance for Improving Catalysts or Just Another Active-Phase Carrier?

There is an obvious gap between efforts dedicated to the control of chemicophysical and morphological properties of catalyst active phases and the attention paid to the search of new materials to be employed as functional carriers in the upgrading of heterogeneous catalysts. Economic constraints and common habits in preparing heterogeneous catalysts have narrowed the selection of active-phase carriers to a handful of materials: oxide-based ceramics (e.g. Al₂O₃, SiO₂, TiO₂, and aluminosilicates-zeolites) and carbon. However, these carriers occasionally face chemicophysical constraints that limit their application in catalysis. For instance, oxides are easily corroded by acids or bases, and carbon is not resistant to oxidation. Therefore, these carriers cannot be recycled. Moreover, the poor thermal conductivity of metal oxide carriers often translates into permanent alterations of the catalyst active sites (i.e. metal active-phase sintering) that compromise the catalyst performance and its lifetime on run. Therefore, the development of new carriers for the design and synthesis of advanced functional catalytic materials and processes is an urgent priority for the heterogeneous catalysis of the future. Silicon carbide (SiC) is a non-oxide semiconductor with unique chemicophysical properties that make it highly attractive in several branches of catalysis. Accordingly, the past decade has witnessed a large increase of reports dedicated to the design of SiC-based catalysts, also in light of a steadily growing portfolio of porous SiC materials covering a wide range of well-controlled pore structure and surface properties. This review article provides a comprehensive overview on the synthesis and use of macro/mesoporous SiC materials in catalysis, stressing their unique features for the design of efficient, cost-effective, and easy to scale-up heterogeneous catalysts, outlining their success where other and more classical oxide-based supports failed. All applications of SiC in catalysis will be reviewed from the perspective of a given chemical reaction, highlighting all improvements rising from the use of SiC in terms of activity, selectivity, and process sustainability. We feel that the experienced viewpoint of SiC-based catalyst producers and end users (these authors) and their critical presentation of a comprehensive overview on the applications of SiC in catalysis will help the readership to create its own opinion on the central role of SiC for the future of heterogeneous catalysis.

Two-Dimensional Silicon Carbide: Emerging Direct Band Gap Semiconductor

As a direct wide bandgap semiconducting material, two-dimensional, 2D, silicon carbide has the potential to bring revolutionary advances into optoelectronic and electronic devices. It can overcome current limitations with silicon, bulk SiC, and gapless graphene. In addition to SiC, which is the most stable form of monolayer silicon carbide, other compositions, i.e., SixCy, are also predicted to be energetically favorable. Depending on the stoichiometry and bonding, monolayer SixCy may behave as a semiconductor, semimetal or topological insulator. With different Si/C ratios, the emerging 2D silicon carbide materials could attain novel electronic, optical, magnetic, mechanical, and chemical properties that go beyond those of graphene, silicene, and already discovered 2D semiconducting materials. This paper summarizes key findings in 2D SiC and provides insight into how changing the arrangement of silicon and carbon atoms in SiC will unlock incredible electronic, magnetic, and optical properties. It also highlights the significance of these properties for electronics, optoelectronics, magnetic, and energy devices. Finally, it will discuss potential synthesis approaches that can be used to grow 2D silicon carbide.

Origins of Dirac cone formation in AB3 and A3B (A, B = C, Si, and Ge) binary monolayers

Compared to the pure two-dimensional (2D) graphene and silicene, the binary 2D system silagraphenes, consisting of both C and Si atoms, possess more diverse electronic structures depending on their various chemical stoichiometry and arrangement pattern of binary components. By performing calculations with both density functional theory and a Tight-binding model, we elucidated the formation of Dirac cone (DC) band structures in SiC₃ and Si₃C as well as their analogous binary monolayers including SiGe₃, Si₃Ge, GeC₃, and Ge₃C. A “ring coupling” mechanism, referring to the couplings among the six ring atoms, was proposed to explain the origin of DCs in AB₃ and A₃B binary systems, based on which we discussed the methods tuning the SiC₃ systems into self-doped systems. The first-principles quantum transport calculations by non-equilibrium Green’s function method combined with density functional theory showed that the electron conductance of SiC₃ and Si₃C lie between those of graphene and silicene, proportional to the carbon concentrations. Understanding the DC formation mechanism and electronic properties sheds light onto the design principles for novel Fermi Dirac systems used in nanoelectronic devices.

Iron-embedded C2N monolayer: a promising low-cost and high-activity single-atom catalyst for CO oxidation

CO oxidation by O₂ on an Fe-embedded C₂N monolayer would proceed via a two-step mechanism. Both the steps are energetically and kinetically favorable.