A remarkable difference in CO2 hydrogenation to methanol on Pd nanoparticles supported inside and outside of carbon nanotubes

An obvious difference was found in CO2 hydrogenation to methanol on Pd nanoparticles (NPs) supported inside and outside of carbon nanotubes (CNTs). The turnover frequency of methanol synthesis on the Pd NPs supported inside of CNTs was 3.7 times those supported outside of CNTs. It was found that the amount of Pd(δ+) species inside of CNTs was much higher than that outside of CNTs. We proposed that one of the major reasons for the difference in CO2 hydrogenation to methanol might be relative to the concentration of the Pd(δ+) species.