Toward an Understanding of Capping Molecules on Pt Nanoparticles for Hydrogenation: the Key Role of Hydroxyl Groups

Preparation of active and stable platinum nanoparticles (Pt NPs) for hydrogenation is of great importance. Herein, a joint experimental and theoretical study has been conducted to investigate the role of capping molecules on Pt NPs for hydrogenation. Both small biomolecules of adenine, D-ribose, adenosine, and 2 '-deoxyadenosine and macromolecule of dextran have been studied as capping agents of Pt NPs. Kinetic data are collected and fitted for deep insight and clear comparison of Pt activity. TEM, SEM, XRD, nitrogen adsorption-desorption were employed to characterize the obtained catalysts. DFT calculations have been carried out to investigate the exact interactions in this system. A volcano plot is obtained between the adsorption energy of 4-NP on various Pt NPs against reaction rate constant (k), which is in accordance with the Bronsted-Evans-Polanyi (BEP) relation. Moreover, active and stable catalyst (Pt/rGO) has been prepared using dextran as capping agent and rGO as support. The hydrogenation of 4-NP over Pt/rGO can reach 100% conversion in only 2 min. The catalyst can still maintain its activity after solvent removal and long-time storage.