First-principles theoretical study on dry reforming of methane over perfect and boron-vacancy-containing h-BN sheet-supported Ni catalysts

H-assisted CO2 dissociation on PdnPt(4-n)/In2O3 catalysts: a density functional theory study

CO2 hydrogenation into valuable chemical compounds can effectively address the issues of greenhouse gas emissions and energy scarcity. The activation and dissociation processes of CO2 are crucial for its reduction reactions, but the effects of *H adatoms on the C-O cleavage are still confusing. This study investigates the H-assisted CO2 dissociation pathways on the PdnPt(4-n)/In2O3 (n = 0-4) catalysts via DFT calculation. Initially, the adsorption properties of *H2, *COOH, and *HCOO species are calculated. Then, two H-assisted CO2 dissociation channels, i.e., *CO2 + *H → *COOH → *CO + *OH and *CO2 + *H → *HCOO → *CHO + *O, are studied. Results show that Pt and Pd promote the CO2 hydrogenation and C-O bond cleavage reactions, respectively. In comparison to CO2 direct dissociation, the COOH-mediated and HCOO-mediated channels facilitate and impede the C-O bond cleavage, respectively. Overall, the Pd3Pt/In2O3 constituent is suggested for the H-assisted CO2 dissociation reaction. The electronic effects of the PdnPt(4-n) bimetals adjust the stabilities of the intermediates and barriers of the elementary steps, and the interactions between PdnPt(4-n) and In2O3 provide extra sites for the adsorbates and reaction steps. This study reveals the effects of *H on the C-O bond dissociation processes and provides useful insight into designing PdPt/In2O3 catalysts for CO2 hydrogenation reactions.

The role of Mo species in Ni-Mo catalysts for dry reforming of methane

The Ni-Mo catalyst has attracted significant attention due to its excellent coke-resistance in dry reforming of methane (DRM) reaction, but its detailed mechanism is still vague. Herein, Mo-doped Ni (Ni-Mo_x) and MoO_x adsorbed Ni surfaces (MoO_x@Ni) are employed to explore the DRM reaction mechanism and the effect of coke-resistance. Due to the electron donor effect of Mo, the antibonding states below the Fermi level between Ni and C increase and the adsorption of C decrease, thereby inhibiting the carbonization of Ni. On account of the strong Mo and O interaction, more O atoms gather around Mo, which inhibits the oxidation of Ni and may promote the formation of MoO_x species on the Ni-Mo catalyst. The presence of Mo-O species promotes the carbon oxidation, forming a unique redox cycle (MoO_x ↔ MoO_x-1) similar to the Mars-van Krevelen (MvK) mechanism, explaining the excellent anti-carbon deposition effect on the Ni-Mo catalyst.

Recent Progress in Fabrication and Application of BN Nanostructures and BN-Based Nanohybrids

Due to its unique physical, chemical, and mechanical properties, such as a low specific density, large specific surface area, excellent thermal stability, oxidation resistance, low friction, good dispersion stability, enhanced adsorbing capacity, large interlayer shear force, and wide bandgap, hexagonal boron nitride (h-BN) nanostructures are of great interest in many fields. These include, but are not limited to, (i) heterogeneous catalysts, (ii) promising nanocarriers for targeted drug delivery to tumor cells and nanoparticles containing therapeutic agents to fight bacterial and fungal infections, (iii) reinforcing phases in metal, ceramics, and polymer matrix composites, (iv) additives to liquid lubricants, (v) substrates for surface enhanced Raman spectroscopy, (vi) agents for boron neutron capture therapy, (vii) water purifiers, (viii) gas and biological sensors, and (ix) quantum dots, single photon emitters, and heterostructures for electronic, plasmonic, optical, optoelectronic, semiconductor, and magnetic devices. All of these areas are developing rapidly. Thus, the goal of this review is to analyze the critical mass of knowledge and the current state-of-the-art in the field of BN-based nanomaterial fabrication and application based on their amazing properties.

CO2 adsorption enhancement over Al/C-doped h-BN: A DFT study

Reducing energy barriers of CO₂ being chemisorbed on hexagonal boron nitride (h-BN) is a kernel step to efficiently and massively capture CO₂. In this study, aluminum/carbon (Al/C) atoms are used as dopants to alter surface potential fields of h-BN, which aims at lowering energy barriers of adsorption processes. Through theoretical calculations, direct-adsorption structures/properties of CO₂, joint-adsorption structures/properties of CO₂/H₂O, transition state (TS) energy barriers, effects of temperatures on adsorption energies/TS energy barriers and changes of reaction rate constants over different adsorbents are investigated in detail in order to reveal how doping of Al/C atoms promotes CO₂ adsorption strength over doped h-BN. According to DFT calculation results, the average adsorption energy of CO₂ being directly adsorbed on Al/C-doped h-BN arrives at -59.43 kJ/mol, which is about 5 times as big as that over pure h-BN. As to the average adsorption energy of CO₂/H₂O and relevant TS energy barrier, they are modified to -118.89 kJ/mol and 40.23 kJ/mol over Al/C-doped h-BN in contrast with -33.91 kJ/mol and 1695.11 kJ/mol over pure h-BN, respectively. What is more, based on thermodynamic analyses and reaction dynamics, the average desorption temperatures of CO₂(/H₂O) are promoted over doped h-BN and the temperature power exponent is negatively correlated with the activation energy in the Arrhenius equation form. The complete understanding of this study would supply crucial information for applying Al/C-doped h-BN to effectively capturing CO₂ in real industries.

Coking-resistant dry reforming of methane over Ni/γ-Al2O3 catalysts by rationally steering metal-support interaction

The coking issue is the main challenge for dry reforming of methane (DRM) over Ni-based catalysts. Herein, we excavate the reasons for the enhanced coking resistance of the bounded Ni over the free state Ni in Ni/γ-Al₂O₃ catalysts for DRM. Rational metal-support interaction of the bounded Ni would facilitate desorption of CO, thus suppressing CO disproportionation and decreasing carbon deposition. The higher activity of the bounded Ni is ascribed to better methane cracking ability, stronger adsorption, and activation of CO₂ by forming polydentate carbonate. The better activation of CO₂ over the bounded Ni would also contribute to the gasification of formed coke. We gain an insight into the anti-coking mechanism of DRM determined by metal-support interaction in Ni/γ-Al₂O₃ catalysts through mechanistic studies. It is believed that our findings would enlighten the design of more efficient catalysts for DRM.

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The anti-coking ability of the bounded Ni is better than the free state Ni

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The bounded Ni has a stronger ability to activate CO₂ to produce active O∗ species

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High reactivity and stable polydentate carbonate enables efficient reaction

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Rational metal-support interaction results in good resistance to CO poisoning