The Challenge

A new catalytic system, Pd/Fe₂O₃, developed by the team shows promise with its high selectivity and more energy efficient conversion. However, the active sites responsible for the efficiency of this reaction, and the exact role played by the Pd and Fe components, have not been identified. The extremely small size of Pd-containing particles on the surface of the iron oxide prevented analysis using diffraction techniques.

The Solution

The researchers teamed up with Diamond scientists to perform Extended X-ray Absorption Fine Structure (EXAFS) measurements at the Pd K-edge. They investigated both the local structure of the  Pd/Fe₂O₃ catalyst and the Pd particle size before (poor CH₃OH selectivity) and after extensive reduction (good CH₃OHselectivity). EXAFS measurements do not require a crystalline sample and are sensitive to the element of interest, in this case Pd, allowing investigation of the very small particles. The EXAFS studies confirmed the formation and composition of ‘PdFe’ clusters.

The Benefits

These findings indicate that the reaction with ethylene glycol had induced small clusters of palladium and iron to form on the catalyst surface, and it was this chemical combination that produced active sites for this reaction. Knowing this will allow the researchers to further improve their catalyst to optimise its efficiency and specificity.