Integrated CO2 capture and hydrogenation in presence of Ru–Na2ZrO3: An in-situ study

Integrated CO 2 capture and conversion (ICCC) by hydrogenation is a promising strategy to utilize carbon dioxide and this work add to the effort to elucidate the catalytic hydrogenation mechanism using Ru based dual functional materials (DFM). Ru–Na 2 ZrO 3 DFMs, obtained through different wet methods, were evaluated for the first time and the relationship between Ru and support systematically investigated. The thermally stable and cyclable Ru–Na 2 ZrO 3 -a (obtained without filtration step) exhibited CO 2 conversion of 80 % and a higher yield of CO at 400 °C compared to previously tested DFM, while the Na depleted/Zr rich Ru–Na 2 ZrO 3 -b resulted in 90 % selectivity to CH 4 with yield of 1.11 mmol/g at the same temperature. The in-situ experiments have provided conclusive evidence showing that CO 2 hydrogenation on the two Ru DFMs is fundamentally different. In Ru–Na 2 ZrO 3 -a, the monoclinic Na 2 ZrO 3 support acted as the active centre (not as promoter) for CO 2 bridging binding and hydrogenation to CH 4 at the metal-support interface through associative formate pathway with limited further reduction to methane due to lack of H 2 spillover from the small and well dispersed Ru NPs, which results in CO desorption. Conversely, abundant clusters of larger Ru NPs in Ru–Na 2 ZrO 3 -b, led to CH 4 production due to co-existent Ru on-top direct dissociation of CO 2 (preferential) and monodentate formate adsorption and further methanation. Alkali zirconates doped metals, and their synthesis method could thus play a crucial role in designing tuneable heterogeneous catalysis in C 1 chemistry, which could significantly benefit the environment by lowering CO 2 levels, encouraging cleaner industrial practices, supporting a circular economy, and converting waste CO 2 into valuable products. • Ru–Na 2 ZrO 3 was developed for highly effective integrated CO 2 capture and conversion. • Selectivity to CH 4 or CO can be tuned by changing the Ru nanoparticle size and operating temperature. • A CO yield of 1 mmol/g was obtained at 400 °C with Ru–Na 2 ZrO 3 -a. • Na 2 ZrO 3 support acted as the active center for the CO 2 bridging binding in Ru–Na 2 ZrO 3 -a favouring RWGS. • Ru clusters promoted by 4 %Na in Ru–Na 2 ZrO 3 -b led to CH 4 production due to Ru on-top adsorption.