Solvent-free strategy of multimetallic oxide nanosheets production for dry reforming of methane

This work reports for the first time a solvent-free synthesis strategy for nickel-incorporated single-phase multimetallic oxide nanosheets (LCCN-CA) via the co-melting of citric acid with metal nitrates. The development of stable and efficient catalysts for Dry Reforming of Methane (DRM) is essential for converting methane (CH₄) and carbon dioxide (CO₂) into synthesis gas, which can be further processed into valuable fuels via Fischer-Tropsch synthesis. Notably, LCCN-CA exhibits exceptional stability and activity in DRM, maintaining CO₂ and CH₄ conversion rates of 96 % and 93 %, respectively, over 200 h at 850 °C without phase separation or significant Ni nanoparticle agglomeration (8.2 nm before the reaction to 9.5 nm after 200 h of DRM operation). Density Functional Theory (DFT) calculations reveal that La₂O₃ hinders both CO₂ adsorption and dissociation due to weak physisorption (Er = 0.14 eV), while LCCO facilitates stronger chemisorption of CO₂ (Er = -0.66 eV) to form CO₃^2–. Furthermore, Ni supported on LCCO has a d-band center closer to the Fermi level (−1.38 eV vs. −1.49 eV for La₂O₃), enhancing electron donation and facilitating methane dehydrogenation. These electronic effects are critical for weakening C–H bonds during methane activation, leading to lower reaction energies and activation barriers compared to Ni/ La₂O₃. This facile synthesis method not only opens new avenues for preparing high-entropy material nanosheets but also holds promise for advancing sustainable energy conversion processes, addressing global challenges related to greenhouse gas emissions and energy resource scarcity.