Both Ru/SiO2 and Ru/12%Ti-SiO2 underwent further testing at 300 °C for 50 h to assess their stability. As shown in Fig. , their selectivity to CH4 remains at 100% throughout 50 h runtime. Surprisingly, Ru/12%Ti-SiO2 exhibits a gradual increase in CO2 conversion from 24% to 39% within the first 10 h and stabilizes thereafter. The observation of induction period suggests that more active sites may be formed during the introduction of CO2/H2 at 300 °C (higher than the reduction temperature of 200 °C). This could be due to a more pronounced interface formation between Ru and TiO2 under the reaction gas mixtures at high temperature . In contrast, Ru/SiO2 exhibits continuous activity loss from 8% to 4% during 50 h on stream, likely due to the sintering of Ru nanoparticles.