Enhanced catalytic activity of palladium nanoparticles confined inside porous carbon in methanol electro-oxidation

Abstract

The effects of the confinement of Pd nanoparticles (NPs) inside hollow carbon matrices are evaluated based on their performance in methanol (MeOH) electro-oxidation (EOx). The performance of three catalyst systems were compared: (1) Pd NPs exclusively confined inside the hollow carbon NPs, (2) Pd NPs distributed between the pores and the surface of porous carbon and (3) Pd NPs bound to the surface of activated charcoal. When NPs are exclusively confined, the electrocatalytic activity improves due to the higher proximity of the NPs to the reactants inside the cavity and minimal leaching of the NPs over 300 cycles. NP confinement yields a high anodic peak current density (AP-CD) of 142 mA cm⁻² (626 cm² mg_Pd⁻¹) at a lower anodic potential of −0.3 V and an excellent re-usability, as compared to the partially confined and exposed NPs. A minimal loading of 1.2–2.5 wt% Pd NPs inside the mesoporous carbon resulted in a high electrochemically active surface area (ECSA), which clearly underlines the positive effect of the confinement of metal NPs.