Volcano-type catalytic activity driven by graphitization-dependent electron transfer in Pt@C core-shell catalysts.

Carbon-encapsulated metal catalysts can have a high stability. The catalytic activation mechanism of the inert carbon shell requires further investigation. We prepared platinum-core carbon-shell catalysts on activated carbon supports. The graphitization degree of the carbon layer was tuned through pyrolysis temperature control. The catalysts were tested in the selective hydrogenation of p-chloronitrobenzene. The intact carbon shell physically isolates the metal core. All coated samples achieved a target product selectivity above 99%. The catalytic activity exhibited a distinct volcano trend. The sample treated at 800 °C delivered the highest activity. Experimental and theoretical analyses revealed an interfacial electron transfer process. The metal core acts as an electron pump to enrich the carbon surface. The optimal activity originates from a balance between electronic and geometric effects. The electron-rich surface lowers the hydrogen dissociation barrier. The preserved carbon defects serve as necessary adsorption sites. The core-shell structure suppressed metal sintering and the catalyst maintained good stability over 10 reaction cycles. This study provides a basic understanding for the design of highly active carbon-functionalized interfaces.