One of the global challenges is to secure our future energy supply. Additionally, we need to reduce the emission of CO2. Here, we present a chemical conversion that addresses both: it uses CO2 as a chemical feedstock, and converts it to CH4 through hydrogenation using green hydrogen, and sunlight as energy source. The reaction is catalyzed by small Ru nanoparticles supported on Al2O3. The solar energy is coupled into the system via the localized surface plasmon resonance of the Ru nanoparticles. The catalyst is prepared through impregnation of Al2O3 with a Ru salt, and subsequent reduction. The composition and structure of the catalyst are extensively studied using XRD, (S)TEM and ICP-MS. The optical properties of the catalyst powders are determined using UV-VIS-NIR spectrophotometry. The CH4 production rate was studied at different temperatures, both under heating (dark) and irradiation with a solar simulator (AM 1.5, light). Irradiation experiments were carried out whilst keeping the temperature constant. Fig. 1 shows the CH4 production rate for experiments in the dark and under sunlight illumination at temperatures between 135○C and 190○C (reaction time 0.5 h, 500 mg catalyst, mixture of CO2 (16.6%), H2 (66.8%) and N2 (16.6%)). At a temperature higher than 150○C, the production rate is substantially higher under illumination than in the dark. The difference between the production rates increases with increasing reaction temperature. A simple photothermal effect could be excluded. In addition to these experiments, we studied the stability of the catalyst over various reaction cycles. Furthermore, we performed experiments at different sunlight intensities ranging from 1 to 10 suns. In conclusion, we developed an efficient plasmon-assisted conversion of CO2 to methane using sunlight as energy source. The activity of the Ru catalyst is substantially higher under solar illumination when compared to dark. We will present a hypothesis explaining these results.

Plasmon-assisted Ru catalyzed hydrogenation of CO2 to CH4 using sunlight as energy source

256th National Meeting (2018)

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