Low-temperature RWGS enhancement of Pt1-nAun/CeO2 catalysts and their electronic state

Reverse water-gas shift (RWGS) operation at lower temperatures has multiple advantages such as use of low-cost materials and improvement of thermal efficiency. This report demonstrates the enhancement of CO selectivity by Au addition and clarifies the relationship between the enhanced CO selectivity and the density of state (DOS) in the vicinity of the Fermi level (Ef).

Improving the Coke Resistance of Ni-Ceria Catalysts for Partial Oxidation of Methane to Syngas: Experimental and Computational Study

The synthesis of syngas (H₂  : CO=2) via catalytic partial oxidation of methane (CPOM) is studied over noble metal doped Ni-CeO₂ bimetallic catalysts for CPOM reaction. The catalysts were synthesized via a controlled deposition approach and were characterized using XRD, BET-surface area analysis, H₂ -TPR, TEM, Raman and TGA analysis. The catalysts were experimentally and computationally studied for their activity, selectivity, and long-term stability. Although the pure 5Ni/CeO2 catalyst showed high initial activity (∼90%) of CH₄ conversion, it rapidly deactivates around 20% of its initial activity within 140 hours of TOS. Doping of Ni/CeO₂ catalyst with noble metal was found to be coke resistant with the best-performing Ni-Pt/CeO₂ catalyst showed ∼95% methane conversion with >90% selectivity at a temperature of 800 °C, having exceptional stability for about 300 hours of time-on-stream (TOS). DFT studies were performed to calculate the activation barrier for the C-H activation of methane over the Ni, Ni₃ Pt, Ni₃ Pd, and Ni₃ Ru (111) surfaces showed nearly equal activation energy over all the studied surfaces. DFT studies showed high coke formation tendency of the pure Ni (111) having a very small C-C coupling activation barrier (14.2 kJ/mol). In contrast, the Ni₃ Pt, Ni₃ Pd, and Ni₃ Ru (111) surfaces show appreciably higher C-C coupling activation barrier (∼70 kJ/mol) and hence are more resistant against coke formation as observed in the experiments. The combined experimental and DFT study showed Ni-Pt/CeO₂ as a promising CPOM catalyst for producing syngas with high conversion, selectivity and long-term stability suited for future industrial applications.

In-situ atmosphere thermal pyrolysis of spindle-like Ce(OH)CO3 to fabricate Pt/CeO2 catalysts: Enhancing Pt-O-Ce bond intensity and boosting toluene degradation

In this work, a series of spindle-like CeO₂ supports with different contents of surface oxygen vacancies were fabricated by an in-situ atmosphere thermal pyrolysis method. Due to the unique surface physicochemical properties of the modified CeO₂ supports, the interaction between Pt and CeO₂ can be regulated during the synthesis of the Pt/CeO₂ catalyst. The abundant oxygen vacancies on the CeO₂ support could preferentially trap Pt²⁺ ions in solution during the Pt impregnation process and enhance the Pt-CeO₂ interaction in the subsequent reduction process, which results in the strongest Pt-O-Ce bonds formed on the PCH catalysts successfully (0.6% Pt loading on the CH support, which generated by thermal pyrolysis of Ce(OH)CO₃ under H₂ atmosphere). The strong Pt-O-Ce bond would trigger abundant surface oxygen species generated and enhanced the lattice oxygen species transfer from CeO₂ supports to Pt nanoparticles. It was crucial to boosting the toluene catalytic activity. Therefore, the PCH catalyst exhibits the highest activity for toluene oxidation (T₁₀ = 120 °C, T₅₀ = 138 °C, and T₉₀ = 150 °C with WHSV = 60,000 mL g^-1 h^-1) and remarkable durability and water resistance among all catalysts. We also conclude that the Pt-O-Ce bond may be the active site for toluene oxidation by calculating the turnover frequencies (TOF_Pt-O-Ce) value for all Pt/CeO₂ catalysts. Moreover, the DFT calculation indicates that the Pt/CeO₂ catalyst with a strong Pt-O-Ce bond possesses the lowest oxygen absorption energy and higher CO tolerance ability, which leads to excellent catalytic performance for toluene and CO catalytic oxidation.

Engineering well-defined rare earth oxide-based nanostructures for catalyzing C1 chemical reactions

In this review, we summarize the nanostructural engineering and applications of rare earth oxide-based nanomaterials with well-defined compositions, crystal phases and shapes for efficiently catalyzing C1 chemical reactions.

NiO supported on Y2Ti2O7 pyrochlore for CO2 reforming of CH4: insight into the monolayer dispersion threshold effect on coking resistance

An evident monolayer dispersion threshold effect on coking resistance is observed for NiO/Y₂Ti₂O₇ catalysts in DRM reaction. A catalyst with the best activity and anti-coking ability can be fabricated at the monolayer dispersion capacity.

Promising catalytic activity by non-thermal plasma synthesized SBA-15-supported metal catalysts in one-step plasma-catalytic methane conversion to value-added fuels

Plasma-reduced metal nanoparticles encapsulated in an ordered mesoporous silica catalyst (SBA-15) effectively convert methane to liquid oxygenates in assistance of DBD-discharge.

Nanoceria-modified platinum supported on hierarchical zeolites for selective alcohol oxidation

The highly selective oxidation of alcohols to aldehydes has been achieved due to the synergic effect of Pt and CeO2 supported on hierarchical zeolites. The combination of Pt and CeO2 strongly enhances the catalytic performance of the oxidation of benzyl alcohol to benzaldehyde with respect to the isolated materials. In addition, the hierarchical zeolite not only increases the fraction of exposed active sites because of its high surface area that can prevent the aggregation of Pt and CeO2 nanoparticles, but also affects the oxidation state of cerium. The presence of a high content of trivalent Ce species (Ce3+) on the hierarchical zeolite benefits the oxidation reaction, eventually leading to almost 100% yield of an aldehyde product. Moreover, the catalytic performance can be further improved by the easily tunable Si to Al ratio of zeolite catalysts.

Thermally stable core-shell Ni/nanorod-CeO2@SiO2 catalyst for partial oxidation of methane at high temperatures

During partial oxidation of methane (POM), the greatest challenge is to maintain the thermal stability of the catalyst at high temperatures. One of the most effective ways to improve thermal stability is to construct core-shell structure. Herein, using a microemulsion method, we synthesized a core-shell Ni/nanorod-CeO2@SiO2 catalyst, in which the Ni nanoparticles were supported on the CeO2 nanorods and encapsulated by SiO2 shells. Based on a series of characterizations, we found that the Ni particles are of nanosize (2.2 nm) and the thickness of the SiO2 shell is about 8 nm in the core-shell catalyst. Moreover, the Ni/nanorod-CeO2@SiO2 catalyst can perfectly maintain rod-like structures of the CeO2 support and enhance interaction between the metal Ni and CeO2, significantly reducing the sintering of metal Ni particles at high temperatures. Therefore, the as-prepared Ni/nanorod-CeO2@SiO2 catalyst shows high catalytic activity and good thermal stability during the POM reaction.