Single-Atom Ru Alloyed with Ni Nanoparticles Boosts CO₂ Methanation

Designing catalysts to proceed with catalytic reactions along the desired reaction pathways, e.g., CO₂ methanation, has received much attention but remains a huge challenge. This work reports one Ru₁Ni single-atom alloy (SAA) catalyst (Ru₁Ni/SiO₂) prepared via a galvanic replacement reaction between RuCl₃ and Ni nanoparticles (NPs) derived from the reduction of Ni phyllosilicate (Ni-ph). Ru₁Ni/SiO₂ achieved much improved selectivity toward hydrogenation of CO₂ to CH₄ and catalytic activity (Turnover frequency (TOF) value: 40.00 × 10^-3 s^-1), much higher than those of Ni/SiO₂ (TOF value: 4.40 × 10^-3 s^-1) and most reported Ni-based catalysts (TOF value: 1.03 × 10^-3-11.00 × 10^-3 s^-1). Experimental studies verify that Ru single atoms are anchored onto the Ni NPs surface via the Ru₁-Ni coordination accompanied by electron transfer from Ru₁ to Ni. Both in situ experiments and theoretical calculations confirm that the interface sites of Ru₁Ni-SAA are the intrinsic active sites, which promote the direct dissociation of CO₂ and lower the energy barrier for the hydrogenation of CO* intermediate, thereby directing and enhancing the CO₂ hydrogenation to CH₄.