Ni-exsolved La_1-xCa_xNiO₃ perovskites for improving CO₂ methanation

This work investigates the promoting effect of Ca on CO₂ hydrogenation to methane in the highly exsolved Ni particles of La_1-xCa_xNiO₃ perovskite catalysts. TEM images presented that metallic Ni particles are exsolved to the surface under a reducing atmosphere. This exsolution behavior is observed until the Ca ratio (x) becomes 0.4, suggesting that the highly dispersed Ni particles formed by the exsolution can actively adsorb and dissociate H₂ molecules. In-situ DRIFT spectroscopy reveals that the surface Ca-sites effectively adsorb CO₂ molecules to form reactive carbonates species. XPS analyses and CO methanation tests further show that adding Ca negatively charges the adsorption sites and enhances the reactivity of CO. This surface coordination is optimized by incorporating 0.4 of Ca, presenting facile hydrogenation of CO molecules to CH₄. Thus, incorporating 0.4 of Ca into the A-site of LaNiO₃ demonstrated the optimized promoting effect on CO₂ methanation.