The use of supported Pd nanoparticles is ubiquitous in hydrogenation chemistry. From synthetic organic transformations towards high-value products in the pharmaceutical or fragrance industries to crude biomass processing towards commodity chemicals such as monomers often the first choice of catalyst is Pd/C. In this talk, I will highlight two of our ongoing studies which reveal the curious reactivity of Pd nanoparticle catalysts under certain reaction conditions. Firstly, we report the design of a hybrid bio-chemo catalyst by immobilization of a hydrogenase enzyme onto a Pd/C catalyst. In this case, we seek to drive a switch from a purely surface mechanism toward a redox hydrogenation mechanism by coupling two catalytic sites which can then act co-operatively. We demonstrate that this hybrid catalyst can operate with up to six times the rate enhancement for the hydrogenation of alkynes compared to Pd/C alone under challenging aqueous conditions. Secondly, we probe the species present during catalytic hydrogenation/dehydrogenation reactions using Pd nanoparticle catalysts and show that under relatively mild conditions exchange of H/D can occur both with background solvents. These include toluene and xylene where C-H bond breaking at the methyl group is challenging. We also observe the presence of H-radical species which adds to the complex picture of what is occurring at the Pd surface during these reactions.
Simon Freakley completed his MChem at Durham University in 2009 with a year in industry at Johnson Matthey studying Fisher Tropsch catalysis. Following this he completed his PhD in 2012 under the supervision of Prof. Graham Hutchings at the Cardiff Catalysis Institute focused on designing new Pd catalysts for the direct synthesis of hydrogen peroxide with applications in water purification. Following this Simon remained at the CCI as a PDRA holding a JSPS fellowship to work with Prof. Haruta on CO oxidation and a Ser Cymru fellowship while working on projects including methane oxidation and acetylene hydrochlorination. In 2018 Simon moved to the University of Bath as a Prize Research Fellow in Sustainable Technology and was appointed to a Lectureship in 2021. His current research interests include the design of metal oxide catalysts for oxygen evolution reactions, nanoparticle-based catalysts for hydrogenation and dehydrogenation reactions, and integration of plasmonic nanoparticles into catalysis.