Enhanced CO₂ Methanation through Electronic Modification of Ru to Ni in Ni-Al Hydrotalcite-derived Catalysts

Nickle-based catalysts are commonly used for CO₂ methanation. However, there is still potential to improve their catalytic performance under mild conditions. In this study, we synthesized a series of Ru-Ni-Al catalysts from Ru-doped NiAl-hydrotalcite using a hydrothermal method. The Ru-Ni-Al catalyst demonstrated much higher activity for CO₂ methanation than the Ni-Al catalyst that did not have Ru doping. Both experimental results and theoretical calculations indicate that the enhanced performance of the Ru-Ni-Al catalyst is related to electronic interactions between nickel (Ni) and ruthenium (Ru). The Ru sites transfer electrons to the Ni sites, increasing the local electron density of Ni, which enhances the adsorption and activation of H₂. Furthermore, the Ru-Ni metal interface sites improve the adsorption and activation of CO₂. In situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) analysis indicates that adjusting the electronic structure of Ni sites can accelerate the production of intermediates HCOO*, while Ru-Ni intermetallic interface sites can directly dissociate CO₂ into CO*. In addition, CO₂ methanation on the Ru-Ni-Al catalyst follows HCOO*- and CO*-mediated pathways. This study underscores the potential for enhancing CO₂ methanation performance by modulating the electronic structure of Ni sites.