Enhanced CO2 methanation through electronic modification of Ru to Ni in Ni–Al hydrotalcite-derived catalysts

Nickle-based catalysts are commonly used for CO 2 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 CO 2 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 H 2 . Furthermore, the Ru–Ni metal interface sites improve the adsorption and activation of CO 2 . 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 CO 2 into CO∗. In addition, CO 2 methanation on the Ru–Ni–Al catalyst follows HCOO∗- and CO∗-mediated pathways. This study underscores the potential for enhancing CO 2 methanation performance by modulating the electronic structure of Ni sites. The catalytic performance of the Ru–Ni–Al catalyst for CO 2 methanation is significantly improved through electronic interaction between Ru and Ni. The electron-rich Ni sites, derived from the electron transfer of Ru sites, help activate H 2 , produce more hydrides, and speed up the conversion of CO 2 to HCOO∗. Additionally, the formed Ru–Ni metal interface sites aid in the direct dissociation of CO 2 to CO∗. Both HCOO∗- and CO∗-mediated pathways work together to enhance CO 2 methanation on the Ru–Ni–Al catalyst. • A Ru–Ni–Al catalyst with adjustable electron interaction has been developed. • Increasing the local electron density of Ni enhances H 2 activation. • The Ru–Ni metal interface site enhances CO 2 activation. • CO 2 methanation to CH 4 is through HCOO∗- and CO∗-mediated routes. • The presence of hydride in the Ru–Ni–Al catalyst can accelerate HCOO∗ formation.