Nickel Nanoparticles Prepared via Colloidal Synthesis as CO2 Hydrogenation Catalysts on Various Support Materials

Abstract

Conflicting structure-sensitivity trends were reported for CO2 hydrogenation over Ni-based catalyst materials from different laboratories. Colloidal synthesis provides not only great control over catalyst properties which could enable a systematic study of structure sensitivity but also challenges related to ligand removal and metal nanoparticle sintering. Here, we used colloidal synthesis to synthesize Ni nanoparticles of different sizes, deposited them on various supports at constant weight loading, and tested them for catalytic CO2 hydrogenation. The usage of small N-containing ligands, such as mesitylaniline, benzophenone imine, and benzonitrile, yielded Ni nanoparticles with sizes ranging between 1.0 and 4.4 nm. Ni nanoparticles of 2.1 ± 0.3 nm were supported on SiO2, Al2O3, MgAl2O4, CeO2, and TiO2. To remove the ligands, we used an alkylating agent treatment. After a reduction step, the Ni particles remained small on SiO2 but sintered on the other supports, especially on Ni/Al2O3, where Ni particles grew to 20–30 nm. The catalyst materials were tested in CO2 hydrogenation and showed strong variation in activity and selectivity. Overall, this work provides a platform to design and study small Ni metal nanoparticles for structure-sensitivity studies and highlights the challenges for colloidal particle activation and stabilization on different supports in catalytic CO2 hydrogenation.