Effect of Ni Particle Size on the Efficiency of Ni/HAP Grafted Catalysts in the CO 2 Methanation Reaction
Nassima Berroug, Miguel A. Gutiérrez‐Ortiz, Juan R. González‐Velasco, Zouhair BoukhaABSTRACT
CO 2 methanation is a promising route for carbon utilization and renewable energy storage, yet its efficiency strongly depends on the properties of the active metal phase. Herein, Ni/HAP catalysts with Ni particle sizes ranging from 3.9 to 7.0 nm were prepared by varying the calcination temperature ramping rate (TRR), while preserving the textural and basic properties of the support. Increasing particle size enhanced reducibility and progressively relaxed the compressive lattice strain of metallic Ni. Catalytic tests revealed a clear structure–activity relationship, with catalysts prepared at intermediate‐to‐high TRR exhibiting superior low‐temperature methanation activity and high CH 4 selectivity. Among them, Ni/HAP‐(5), containing 6.3 nm Ni particles, showed the highest intrinsic activity, reaching TOF values of 0.28 s − 1 for CO 2 consumption and 0.21 s − 1 for CH 4 formation at 330°C, together with excellent stability. In situ FTIR revealed faster formation and conversion of formate and methoxy intermediates, consistent with more efficient CO 2 activation and faster hydrogenation kinetics. These findings suggest that enhanced catalytic activity is associated with the combined effects of an optimal Ni particle size (6.3 nm) within the investigated range (3.8–7 nm) and a partially relaxed lattice strain.