(509c) Exploring the Impact of Gadolinium on Nickel-Catalyzed CO2 Methanation.

The conversion of CO₂ to methane presents a promising approach for CO₂ utilization, given the ability to integrate methane into existing natural gas infrastructure for power generation. Nickel (Ni) is an attractive methanation catalyst due to its cost-effectiveness, high availability, and promising activity, despite challenges related to coke formation and sintering. To enhance the reactivity of Ni catalysts, various promoting metals have been investigated in conjunction with Ni. In this work, we developed bimetallic Ni catalysts with a gadolinium (Gd) promoter. The impact of these bimetallic structures on CO₂ methanation reactivity and the associated reaction pathway was studied.

We synthesized 3% Ni and 3% Ni-1% Gd catalysts on SiO₂ supports using strong electrostatic adsorption (SEA). Scanning transmission electron microscopy imaging with energy dispersive X-ray spectroscopy maps confirmed the formation of a bimetallic structure between Ni and Gd. From hydrogen temperature-programmed reduction analysis, it was observed that reduction of 3% Ni/SiO₂ started at 315 °C. However, the introduction of 1% Gd to 3% Ni/SiO₂ lowered the reduction temperature to 265 °C, indicating the role of Gd in promoting catalyst reduction at lower temperatures. Via CO₂ temperature-programmed desorption analysis, we observe that 3% Ni-1%Gd/SiO₂ increases the fraction of favorable basic sites for CO₂ methanation by a factor of 15 compared to 3% Ni/SiO₂. The methane production rate of 3% Ni-1% Gd/SiO₂ was found to be 16 times higher than that of 3% Ni/SiO₂. In situ FTIR results revealed that 3% Ni/SiO₂ followed carbonyl and formate pathways, while 3% Ni-1% Gd/SiO₂ exclusively followed the carbonyl pathway. We also note that Gd alone exhibited no activity for CO₂ methanation. In summary, we have demonstrated that Gd is an effective promoter for Ni catalysts resulting in enhanced CO₂ methanation rates compared to monometallic Ni catalysts.