However, this benchmark catalyst was surpassed by another, namely ruthenium nanoparticles on titanium dioxide (Ru/TiO2), achieving nearly complete conversion with 100% selectivity towards methane. This novel catalyst was synthesized by introducing RuCl3 into an aqueous dispersion of TiO2 P90, a commercially available blend of rutile and anatase (See Supplementary Information). This process led to the formation and deposition of ruthenium(III) oxide hydroxide species onto the TiO2 surface, which were subsequently reduced to ruthenium nanoparticles. Analysis by inductively coupled plasma-atomic emission spectroscopy revealed a ruthenium content of 5.5% w/w, corresponding to a ruthenium yield of 96%. Transmission electron microscopy examination demonstrated a uniform distribution of spherical ruthenium nanoparticles on the TiO2 surface, with an average particle size of 1.79 ± 0.51 nm (lognormal distribution). Notably, the productivity of this catalyst could be further enhanced to 127 mmol gcat -1 h -1 by increasing the flow rate.