Turning CO2 to CH4 and CO over CeO2 and MCF-17 supported Pt, Ru and Rh nanoclusters – Influence of nanostructure morphology, supporting materials and operating conditions

Efficient conversion of CO2 into CH4 and CO brings an important opportunity to get valuable feedstock for a variety of industrially important reactions as both CH4 and CO are widely used as starting materials for the synthesis of valuable fuels and chemicals. Herein, we synthesized sub-nanometer (<2nm) Platinum (Pt), Ruthenium (Ru) and Rhodium (Rh) nanoclusters (NCs) via colloidal method; successfully decorated over mesoporous CeO2 and high surface area (HSA) siliceous meso-cellular foam (MCF 17) and tested for high-pressure CO2 reduction at lower temperature range (220–340 °C). Pt and Ru NCs exhibited typical reverse water gas shift (RWGS) and methanation catalytic performance respectively with minimal influence of the nature of support however, Rh NCs showed drastic variations in the product selectivity which exhibited strong influence of the support over the product distribution. Furthermore, Ru NCs (with a relatively lower metal loading ∼ 1 wt%) were found to be highly selective to CH4 (∼99 %) and stable (upto 40 hr time on stream) with either CeO2/MCF 17 at 340 °C; also Ru NCs exhibited comparatively the highest CO2 conversion (∼93 % in case of Ru NCs/CeO2) among the supported metal NCs. HRTEM results showed that metal NCs were homogeneously dispersed with a controlled and uniform particle size (<2nm); no substantial agglomeration of Ru NCs were observed after reaction. Beside the stable dispersion of NCs, Near Ambient Pressure (NAP) in situ XPS of Ru/CeO2 showed that the dynamic Ce3+/Ce4+ ratio of CeO2 can attribute to the high activity and selectivity.