Highly dispersed Ni-based catalysts for CO₂ methanation have been extensively studied over the last decade. However, a highly loaded Ni-based catalyst always results in a large Ni particle size and poor CO₂ methanation activity. In this work, a colloidal solution combustion method was used to prepare a highly loaded Ni–La₂O₃ catalyst (50 wt % Ni) with a small Ni particle size and abundant metal–support interface. The characterizations demonstrated that a Ni–La₂O₃ catalyst prepared in this way has a mesoporous structure and a small Ni particle size. Due to the small Ni particle size and abundant metal–support interface, the highly loaded mesoporous Ni–La₂O₃ catalyst exhibits higher activity and selectivity in CO₂ methanation compared to the Ni–La₂O₃ catalyst prepared by a conventional solution combustion method.

Mesoporous Ni-based catalysts with Ni confined in nanochannels are widely used in CO₂ methanation. However, when Ni loadings are high, the nanochannels are easily blocked by nickel particles, which reduces the catalytic performance. In this work, three-dimensional mesoporous Ni-CeO₂-CSC catalysts with high Ni loadings (20−80 wt %) were prepared using a colloidal solution combustion method, and characterized by nitrogen adsorption–desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM) and H₂ temperature programmed reduction (H₂-TPR). Among the catalysts with different Ni loadings, the 50% Ni-CeO₂-CSC with 50 wt % Ni loading exhibited the best catalytic performance in CO₂ methanation. Furthermore, the 50% Ni-CeO₂-CSC catalyst was stable for 50 h at 300° and 350 °C in CO₂ methanation. The characterization results illustrate that the 50% Ni-CeO₂-CSC catalyst has Ni particles smaller than 5 nm embedded in the pore walls, and the Ni particles interact with CeO₂. On the contrary, the 50% Ni-CeO₂-CP catalyst, prepared using the traditional coprecipitation method, is less active and selective for CO₂ methanation due to the larger size of the Ni and CeO₂ particles. The special three-dimensional mesoporous embedded structure in the 50% Ni-CeO₂-CSC can provide more metal–oxide interface and stabilize small Ni particles in pore walls, which makes the catalyst more active and stable in CO₂ methanation.

Ni-CeO₂/SBA-15-V catalyst was prepared by the impregnation method with vacuum thermal treatment and used for CO₂ methanation reaction. Compared with Ni-CeO₂/SBA-15-air catalyst with thermal treatment in air, the reduced Ni-CeO₂/SBA-15-V catalyst with vacuum thermal treatment exhibited higher Ni dispersion and smaller Ni particle size. In CO₂ methanation reaction, the Ni-CeO₂/SBA-15-V catalyst was more active and selective than the Ni-CeO₂/SBA-15-air catalyst. The good activity and selectivity of Ni-CeO₂/SBA-15-V catalyst should be due to highly dispersed Ni in contact with small CeO₂ particles.

Sintering and carbon deposition are the two main ways to deactivate Ni-based catalysts during methane reforming. Herein, a stable Ni-CeO₂/SiO₂(CSC) catalyst was prepared by a one-step colloidal solution combustion method (CSC) and used for dry reforming of methane. In the catalyst, the small Ni particles were confined by CeO₂ particles and highly dispersed on the surface of SiO₂, forming a spatial confinement structure with a rich Ni-CeO₂ interface in the catalyst. The Ni-CeO₂/SiO₂(CSC) catalyst prepared by the one-step CSC method exhibited superior activity at 700 °C during dry reforming of methane, and the performance of the catalyst was stable after 20 h of reaction with only a small amount of carbon deposition present (1.8%). Due to the spatial confinement effect, Ni was stable and less than 5 nm during reaction. The small Ni particle size and rich Ni-CeO₂ interface reduced the rate of carbon deposition. This colloidal combustion method could be applied to prepare stable metal-based catalysts with rich metal–oxide interfaces for high-temperature reactions.

Using the colloidal solution combustion approach, a three-dimensional mesoporous 5%Ni-CeO₂-M catalyst was developed, with Ni incorporated into the pores, and applied in the dry reforming of methane. Comprehensive characterization revealed that the 5%Ni-CeO₂-M catalyst had a large specific surface area and a three-dimensional mesoporous structure. A rich Ni-CeO₂ interface was formed by closely spaced tiny CeO₂ and NiO nanoparticles within the spherical pore wall. With very little carbon deposition over a 100 h period at 700 °C, the catalyst showed excellent activity and stability. The tiny Ni nanoparticles, along with the substantial Ni-CeO₂ interfaces that make up this three-dimensional in-form mesoporous catalyst, are responsible for the outstanding effectiveness of this 5%Ni-CeO₂-M catalyst.

Ni nanoparticles encapsulated within La₂O₃ porous system (Ni@La₂O₃), the latter supported on SiO₂ (Ni@La₂O₃)/SiO₂), effectively inhibit carbon deposition for the dry reforming of methane. In this study, Ni@La₂O₃/SiO₂ catalyst was prepared using a one-pot colloidal solution combustion method. Catalyst characterization demonstrates that the amorphous La₂O₃ layer was coated on SiO₂, and small Ni nanoparticles were encapsulated within the layer of amorphous La₂O₃. During 50 h of dry reforming of methane at 700 °C and using a weight hourly space velocity (WHSV) of 120,000 mL g_cat⁻¹ h⁻¹, the CH₄ conversion obtained was maintained at 80%, which is near the equilibrium value, while that of impregnated Ni–La₂O₃/SiO₂ catalyst decreased from 63% to 49%. The Ni@La₂O₃/SiO₂ catalyst exhibited very good resistance to carbon deposition, and only 1.6 wt% carbon was formed on the Ni@La₂O₃/SiO₂ catalyst after 50 h of reaction, far lower than that of 11.5 wt% deposited on the Ni–La₂O₃/SiO₂ catalyst. This was mainly attributed to the encapsulated Ni nanoparticles in the amorphous La₂O₃ layer. In addition, after reaction at 700 °C for 80 h with a high WHSV of 600,000 mL g_cat⁻¹ h⁻¹, the Ni@La₂O₃/SiO₂ catalyst exhibited high CH₄ conversion rate, ca. 10.10 mmol g_Ni⁻¹ s⁻¹. These findings outline a simple synthesis method to prepare supported encapsulated Ni within a metal oxide porous structure catalyst for the dry reforming of methane reaction.