Modifying carbon nanotubes supported palladium nanoparticles via regulating the electronic metal–carbon interaction for phenol hydrogenation

Heteroatom doped carbon materials have been synthesized and served as catalyst supports for Pd nanoparticles (NPs). Numerous Pd-carbon catalysts can be produced via single-, dual-, and multi-doping heteroatoms into carbon supports. Therefore, it is highly desired to seek a universal descriptor, regardless of the doping types, in guiding to the design of efficient catalysts. The electronic state of Pd affected by carbon supports is crucial in catalysis, which can be described by the binding energy (BE) accurately and conveniently using X-ray photon spectroscopy. In this work, the single (dual)-doped carbon nanotubes (CNTs) with tunable doping degrees were synthesized via thermal pyrolysis of heteroatom-containing precursors, accompanied by the defluorination of fluorinated CNTs. Density functional theory results show that the charge distributions of the doped-CNTs are determined by the doping configurations. After loading Pd NPs, the charge of the support redistributes. Meanwhile, the BEs of Pd⁰ 3d5/2 change correspondingly due to the electronic metal–carbon interaction (EMCI). Eventually, Pd NPs with different electronic states show the difference in the turnover frequency of phenol hydrogenation. Therefore, the electronic state of Pd NPs can be considered as a proper descriptor for estimating the catalytic performance and indicator for developing highly efficient catalysts.