The preparation of Ru nanoparticles supported on γ-Al₂O₃ followed by chemical reduction using RuCl₃ as a precursor is demonstrated, and their properties are compared to Ru nanoparticles supported on γ-Al₂O₃ prepared by impregnation of γ-Al₂O₃ with Ru₃(CO)₁₂ and subsequent thermal decomposition. The Ru nanoparticles resulting from chemical reduction of RuCl₃ are slightly larger (1.2 vs. 0.8 nm). In addition, Ru nanoparticles were deposited on Stöber SiO₂ using both deposition techniques. These particles were larger than the ones deposited on γ-Al₂O₃ (2.5 and 3.4 nm for chemical reduction and thermal decomposition, respectively). Taking into account the size differences between the Ru nanoparticles, all catalysts display similar activity (0.14–0.63 mol·g_Ru⁻¹·h⁻¹) and selectivity (≥99%) in the sunlight-powered Sabatier reaction. Ergo, the use of toxic and volatile Ru₃(CO)₁₂ can be avoided, since catalysts prepared by chemical reduction of RuCl₃ display similar catalytic performance.