Optimization of Co-Ni-Mg-Al mixed-oxides CO2 methanation catalysts with solution combustion synthesis: On the importance of Co incorporation and basicity

•One-step synthesis favors dissociation of Ni and Co to the support oxide matrix.•Separate deposition of Co and Ni results in an enhancement of the surface basicity.•Nickel coordination number is lower if synthesis is split into two steps.•Two-step synthesis prevents Ni dissociation to the support.•Deposition of Ni separately from Co results in higher catalytic activity.