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The development of coke-resistant catalysts for dry reforming of methane (DRM) is critical for sustainable syngas production. To suppress coking, this study investigates the use of Ti3C2Tx and Nb2CTx MXenes as support for Ni catalysts in DRM and benchmarked their performance with conventional catalysts (Ni/γ-Al2O3, Ni/MgAl2O4, and Ni/SiO2). The MXenes were etched using NH4HF2, and a 10 wt% Ni loading on the supports was achieved via wet impregnation synthesis. Ni/Nb2CTx showed the highest H2 consumption (10.4 mmolH2/gcat). DRM was conducted at 700 °C using a feed ratio of CH4/CO2 of 1:1 and a high space velocity (90,000 ml/gcat h). Unlike the other catalysts, Ni/Nb2CTx pre-reduced at 500 °C exhibited a low normalized coking rate (4.41 µgcoke/mmolCH4), a high overall reaction rate (104 ± 13 mmol/gNi.min), and the highest turnover frequency at 16.7 s−1. The apparent CO2 reaction rate at these conditions was similar to the CH4 rate, suggesting that the low coking rate was due to the efficient utilization of dissociated oxygen. Molecular dynamics (MD) simulations performed on NbC(111) and TiC(111) surfaces at 700 °C and atmospheric pressure reveal that the efficient utilization was mediated by rapid oxygen spillover. The average oxygen velocity from the simulations was slightly higher on NbC (0.0969 Å/fs) than on TiC (0.0961 Å/fs). Both MXene supports are transformed to stable oxycarbides during DRM, and Nb2CTx was stable for 50 h TOS. This investigation not only highlights the potential of Ni/Nb2CTx as a coke- and sintering-resistant catalyst but also demonstrates the role of MXenes supports in the DRM process. 

The synthesis of carbon nanotubes has attracted considerable interest due to their unique physical and structural properties. Despite notable experimental advancements, particularly in chemical vapor deposition (CVD) techniques, a significant gap remains in developing comprehensive mechanistic models that correlate nanotube growth dynamics with gas-phase composition. The CVD involves a complex interplay of multiscale phenomena, including hydrocarbon transport within the reactor and surface reactions on catalyst nanoparticles, collectively contributing to nucleation and growth. This paper introduces a computational modeling framework that integrates these phenomena by leveraging density functional theory energy data, microkinetic modeling, and computational fluid dynamics. The proposed approach addresses the challenges inherent in this multiscale-multiphysics problem, providing insights into nanotube growth as a function of gas composition and transport, temperature, and catalyst properties. The simulation results show strong agreement with experimental trends, highlighting the significance of gas-phase reactions in a mixed hydrocarbon feedstock and the effects of catalyst deactivation. 

The interfacial contact between TiO 2 and graphitic carbon in a hybrid composite plays a critical role in electron transfer behavior, and in turn, its photocatalytic efficiency. Herein, we report a new approach for improving the interfacial contact and delaying charge carrier recombination in the hybrid by wrapping short single-wall carbon nanotubes (SWCNTs) on TiO 2 particles (100 nm) via a hydration-condensation technique. Short SWCNTs with an average length of 125 ± 90 nm were obtained from an ultrasonication-assisted cutting process of pristine SWCNTs (1–3 μm in length). In comparison to conventional TiO 2 –SWCNT composites synthesized from long SWCNTs (1.2 ± 0.7 μm), TiO 2 wrapped with short SWCNTs showed longer lifetimes of photogenerated electrons and holes, as well as a superior photocatalytic activity in the gas-phase degradation of acetaldehyde. In addition, upon comparison with a TiO 2 –nanographene “quasi-core–shell” structure, TiO 2 -short SWCNT structures offer better electron-capturing efficiency and slightly higher photocatalytic performance, revealing the impact of the dimensions of graphitic structures on the interfacial transfer of electrons and light penetration to TiO 2 . The engineering of the TiO 2 –SWCNT structure is expected to benefit photocatalytic degradation of other volatile organic compounds, and provide alternative pathways to further improve the efficiency of other carbon-based photocatalysts. 

Nanosized, well-dispersed titania particles were synthesized via a hydrothermal method using multiwalled carbon nanotubes (MWCNTs) as structural modifiers during the nucleation process to decrease aggregation. Synthesized TiO 2 /MWCNT composites containing different amounts of MWCNTs were characterized using N 2 physisorption, XRD, spectroscopic techniques (Raman, UV-visible, and X-ray photoelectron), and electron microscopy to illuminate the morphology, crystal structure, and surface chemistry of the composites. Photocatalytic performance was evaluated by measuring the degradation of acetaldehyde in a batch reactor under UV illumination. Average rate constants decrease in the following order: TiO 2 /MWCNT-1% > TiO 2 > TiO 2 /MWCNT-5%. Addition of MWCNTs beyond the optimum loading ratio of 1:100 (MWCNT:TiO 2 ) diminishes the effectiveness of the photocatalyst and the synergistic effect between MWCNTs and TiO 2 . The primary mechanism for photocatalytic activity enhancement in TiO 2 /MWCNT-1% is thought to be due to increased porosity, hydroxyl enrichment on the surface, and high dispersion of TiO 2 particles.