Tailored synthesis of a palladium catalyst supported on nitrogen-doped carbon nanotubes for gas-phase formic acid decomposition: A strong influence of a way of nitrogen doping

Abstract

Palladium catalysts supported on different nitrogen-containing carbon nanotubes (N-CNTs) were successfully used in the continuous gas-phase formic acid decomposition for hydrogen production. A strong influence of a way of carbon tubes doping by nitrogen on the activity of catalysts comprising metallic nanoparticles of ca. 1 nm in size and single-atom Pd2+ species was found. A key role of the single-atom species, demonstrating excellent stability in various chemically aggressive media, in the catalyst activity was discovered when bamboo-like N-CNTs synthesized by catalytic chemical vapor deposition were used as a support. A substantial increase in the activity of Pd nanoparticles was achieved by the use of N-СNTs prepared by the post-treatment of oxidized multiwalled carbon nanotubes by ammonia resulting in the formation of the dominating surface amine groups. The combination of the electron-rich palladium nanoparticles and surface amine groups leads to an increase in the TOF value by a factor of 7 at 70 °C. The catalyst operates stable at >99 % selectivity to hydrogen with the mass specific performance 200 l H2/gPd ⋅ h.