Highly Stable Single-Atom Catalyst with Ionic Pd Active Sites Supported on N-Doped Carbon Nanotubes for Formic Acid Decomposition

Single-atom catalysts with ionic Pd active sites supported on nitrogen-doped carbon nanotubes have been synthesized with a palladium content of 0.2-0.5 wt %. The Pd sites exhibited unexpectedly high stability up to 500 degrees C in a hydrogen atmosphere which was explained by coordination of the Pd ions by nitrogen-containing fragments of graphene layers. The active sites showed a high rate of gas-phase formic acid decomposition yielding hydrogen. An increase in Pd content was accompanied by the formation of metallic nanoparticles with a size of 1.2-1.4 nm and by a decrease in the catalytic activity. The high stability of the single-atom Pd sites opens possibilities for using such catalysts in high-temperature reactions.