Tiny Ni particles dispersed in platelet SBA-15 materials induce high efficiency for CO2 methanation

Niobium Modification of CeO2 Tuning Electron Density of Nickel-Ceria Interfacial Sites for Enhanced CO2 Methanation

CO2 methanation has attracted considerable attention as a promising strategy for recycling CO2 and generating valuable methane. This study presents a niobium-doped CeO2-supported Ni catalyst (Ni/NbCe), which demonstrates remarkable performance in terms of CO2 conversion and CH4 selectivity, even when operating at a low temperature of 250 °C. Structural analysis reveals the incorporation of Nb species into the CeO2 lattice, resulting in the formation of a Nb-Ce-O solid solution. Compared with the Ni/CeO2 catalyst, this solid solution demonstrates an improved spatial distribution. To comprehend the impact of the Nb-Ce-O solid solution on refining the electronic properties of the Ni-Ce interfacial sites, facilitating H2 activation, and accelerating the hydrogenation of CO2* into HCOO*, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis and density functional theory (DFT) calculations were conducted. These investigations shed light on the mechanism through which the activity of CO2 methanation is enhanced, which differs from the commonly observed CO* pathway triggered by oxygen vacancies (OV). Consequently, this study provides a comprehensive understanding of the intricate interplay between the electronic properties of the catalyst's active sites and the reaction pathway in CO2 methanation over Ni-based catalysts.

Recent Advances in the Applications of Mesoporous Silica in Heterogenous Catalysis

Mesoporous silica is a class of silica material with a large specific surface area, high specific pore volume and meso-sized pores. These properties make mesoporous silica a good choice of...

Review of CO2 Reduction on Supported Metals (Alloys) and Single-Atom Catalysts (SACs) for the Use of Green Hydrogen in Power-to-Gas Concepts

The valorization of carbon dioxide by diverting it into useful chemicals through reduction has recently attracted much interest due to the pertinent need to curb increasing global warming, which is mainly due to the huge increase of CO2 emissions from domestic and industrial activities. This approach would have a double benefit when using the green hydrogen generated from the electrolysis of water with renewable electricity (solar and wind energy). Strategies for the chemical storage of green hydrogen involve the reduction of carbon dioxide to value-added products such as methane, syngas, methanol, and their derivatives. The reduction of CO2 at ambient pressure to methane or carbon monoxide are rather facile processes that can be easily used to store renewable energy or generate an important starting material for chemical industry. While the methanation pathway can benefit from existing infrastructure of natural gas grids, the production of syngas could be also very essential to produce liquid fuels and olefins, which will also be in great demand in the future. In this review, we focus on the recent advances in the thermocatalytic reduction of CO2 at ambient pressure to basically methane and syngas on the surface of supported metal nanoparticles, single-atom catalyst (SACs), and supported bimetallic alloys. Basically, we will concentrate on activity, selectivity, stability during reaction, support effects, metal-support interactions (MSIs), and on some recent approaches to control and switch the CO2 reduction selectivity between methane and syngas. Finally, we will discuss challenges and requirements for the successful introduction of these processes in the cycle of renewable energies. All these aspects are discussed in the frame of sustainable use of renewable energies.

Influence of sodium-modified Ni/SiO2 catalysts on the tunable selectivity of CO2 hydrogenation: Effect of the CH4 selectivity, reaction pathway and mechanism on the catalytic reaction

CO₂ hydrogenation over Ni/SiO₂ catalysts with and without Na additives was investigated in terms of the catalytic activity, selectivity of CO₂ methanation and reaction mechanism. Na additives could cause the formation of Na₂O species that might deposit on the Ni surface of Ni/SiO₂ (NiNa_x/SiO₂). When the Ni metal is partially covered with Na₂O species, a highly positive charge on the Ni metal could occur compared to the original Ni/SiO₂ catalyst. The addition of Na to the Ni/SiO₂ catalyst could influence selectivity toward CO formation. The adsorbed formic acid is the major intermediate on the Ni/SiO₂ catalyst during CO₂ hydrogenation. The formic acid species might decompose into adsorbed CO complexes in the forms of linear CO, bridged CO and multibonded CO. CH₄ formation should be ascribed to the hydrogenation of these adsorbed CO complexes. The Ni/SiO₂ catalyst with the Na additive might have very weak ability for H₂ and CO adsorption, thus making it difficult for CO methanation to occur. The hydrogen carbonate species adsorbed on the NiNa_x/SiO₂ catalysts were proposed to be the key intermediate, and they might decompose to CO or be hydrogenated to form CH₄.

Carbamate-Isocyanurate-Bridged Periodic Mesoporous Organosilica for van der Waals CO2 Capture

We synthesized a new organosiloxane bridge on the basis of an isocyanurate derivative through a simple melt-fusion approach by the reaction of 3-isocyanatopropyltriethoxysilane (IPTES) with 1,3,5-tris(2-hydroxyethyl)-1,3,5-triazinane-2,4,6(1H,3H,5H)-trione (THEIC). The obtained carbamate-isocyanurate-based organosiloxane bridge precursor was used for the preparation of chemo- and thermostable periodic mesoporous organosilica (PMO-THEIC) on condensation with tetrathoxysilane silicon precursor through a soft-template approach. Furthermore, the synthesized PMO-THEIC with unique surface functionality was investigated for CO₂ capture. The results show that the PMO-THEIC has higher activity than pure SBA-15 for CO₂ capture due to the high affinity of carbamate functionalities embedded within the pore walls toward CO₂ molecules. The affinity of organosiloxane bridge for CO₂ molecules is mainly facilitated via the van der Waals force with carbamate functional groups rather than the isocyanurate ring, according to the density functional calculations.