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[Display omitted] • Ni phyllosilicate was firstly synthesized by a modified microwave synthesis method. • Surfactant modification led to ultrahigh specific surface area of 535 m2 g−1 and ultrathin layer of Ni phyllosilicate of only 1.43 nm. • Hexadecyl trimethyl ammonium bromide showed higher promotion effect compared with P123 and F127. • The special structure resulted in competitive catalytic activity for CO 2 methanation. • This catalyst could exhibit high stability for 100 h in a long-term test. The traditional techniques for the synthesis of nickel phyllosilicates usually time-consuming and energy-intensive, which often lead to the formation of layers with excessive thickness due to uncontrolled crystal growth. In order to overcome these challenges, this work introduces a microwave-assisted synthesis strategy to facilitate the synthesis of Ni-phyllosilicate-based catalysts within an exceptionally short duration of only five minutes, attaining a peak temperature of merely 102 °C. To enhance the specific surface area and to increase the exposure of active sites, an investigation was conducted involving three surfactants. The employment of hexadecyl trimethyl ammonium bromide (CTAB) has yielded remarkable results, with an ultrahigh specific surface area reaching 535 m2 g−1 and an ultrathin lamellar thickness of 1.43 nm. The catalyst exhibited an impressive CO 2 conversion of 81.7 % at 400 °C, 60 L g−1 h−1, 0.1 MPa. It also demonstrated a substantial turnover frequency for CO 2 (TOF CO2) of 5.4 ± 0.1 × 10−2 s−1, alongside a relatively low activation energy (E a) of 80.74 kJ·mol−1. Moreover, the catalyst maintained its high stability over a period of 100 h and displayed high resistance to sintering. To further elucidate growth temperature gradient of the catalyst and concentration gradient of the materials involved, COMSOL Multiphysics (COMSOL) simulations were effectively utilized. In conclusion, this work breaks the limitation associated with traditional, laborious synthesis methods for Ni-phyllosilicates, which can produce materials with high surface area and thin-layer characteristics. [ABSTRACT FROM AUTHOR]

[Display omitted] • The ultrathin Ni-phyllosilicate was successfully synthesized by ball milling method. • H 2 O 2 played a crucial role of pore-forming reagent to create defects in Ni-phyllosilicate. • Nickel acetylacetonate was the optimal nickel salt precursor to form Ni-phyllosilicate. • Metal utilization rate was significantly improved owing to the ultrathin defect-rich structure. • The optimum catalyst exhibited enhanced low-temperature activity for CO 2 methanation. To address the problems of low metal utilization rate and poor low-temperature activity of the nickel phyllosilicate catalysts for CO 2 methanation, this work prepared ultrathin defect-rich Ni-phyllosilicate through ball milling method in the presence of H 2 O 2 modifier, which simultaneously created active sites with more quantity and higher quality. The instantaneous temperature and high pressure derived from the collision and friction of grinding balls provided driving force for the Ni-phyllosilicate synthesis, and the shear force destroyed the interlayer forces to construct the ultrathin layers. H 2 O 2 molecule could insert the layers and dissociate to O 2 bubbles, whose cavitation effect created holes and defects in the nickel phyllosilicate nanosheets and SiO 2 spheres. H 2 O 2 amount was crucial for the defect construction and the optimum Ni-AA-1H catalyst possessed the ultrathin nanosheet of 0.68 nm and high Ni dispersion of 15.6 %, whose TOF CO2 reached 3.76 × 10−2 s−1 at 160 °C. The in-situ DRIFTS results confirmed the enhanced low-temperature activity and the HCOO− reaction pathway over Ni-AA-1H for CO 2 methanation. Nickel precursor effect was also investigated, and nickel acetylacetonate was determined as the optimal one compared with nickel acetate and nickel chloride, owing to the high steric effect of CH 3 COCHCOCH 3 − group and strong basicity environment during ball milling process. [ABSTRACT FROM AUTHOR]

Addressing the problems of easy collapse, Ni sintering and low catalytic activity over the nanotubular nickel phyllosilicate catalyst, the Mg species was doped via a simple hydrothermal method to construct the nanotubular Ni-Mg bimetallic phyllosilicate solid solution. The high thermal stability, nonreducible property and strong basicity of magnesium species led to the enhancement of anti-collapse, Ni-sintering resistance and basicity. As a result, the fine Ni particles and enhanced H 2 and CO 2 chemisorption and activation properties resulted in boosting the catalytic activity of both CO 2 methanation and CH 4 -CO 2 reforming reactions. The Ni/Mg ratios and the reduction temperatures were detailed optimized, and the 600oC-reduced Ni 8 Mg 2 -NT catalyst with the Ni/Mg ratio of 8:2 was the optimal, which also exhibited high long-term stability. In short, the formed Ni-Mg-phyllosilicate solid solution structure and the special interactions of different species brought about high catalytic performance of the nanotubular Ni-Mg phyllosilicate catalyst. [Display omitted] • The nanotubular Ni-Mg bimetallic phyllosilicate solid solution was synthesized. • Nanotubular Ni-Mg phyllosilicate obtained high anti-collapse and Ni-sintering resistance properties. • The Ni/Mg ratio of 8:2 and the reduction temperature of 600 oC were the optimum. • This catalyst was versatile for both CO 2 methanation and CH 4 -CO 2 reforming reactions. [ABSTRACT FROM AUTHOR]