Controllable coordination of a phosphotungstic acid-modified carbon matrix for anchoring Pt species with different sizes: from single atoms and subnanoclusters to nanoparticles

Abstract

Pt species with different sizes uniformly dispersed on a phosphotungstic acid (PTA) modified carbon matrix (PTA-C) were controllably synthesized by manipulating the coordination environment. The results indicate that high-density and well-defined isolated single Pt atoms (Pt SAs) existed in the Pt SAs_0.5/PTA-C sample and the Pt SAs carried positive charges due to the coordination of Pt with oxygen atoms of the PTA-C support. Better catalytic activity and selectivity for the hydrogenation of aromatic nitro-compounds are obtained over Pt SAs_0.5/PTA-C than its nanocatalyst counterparts and hybrid catalysts. The Pt SAs_0.5/PTA-C catalyst shows nearly 100% conversion of nitrobenzene, 99% selectivity to m-bromonitrobenzene and TOF was up to 2062 h⁻¹ with only 0.5 mmol‰ catalyst. The excellent catalytic performance is due to the well-defined and high-density Pt SA sites, which make H₂ dissociate with a low barrier and then rapidly spill over to the substrate and the intermediates. Pt SAs_0.5/PTA-C retained over 90% conversion over five cycles, exhibiting the outstanding stability of Pt SAs.