Multifunctional Catalytic Properties of Pd/CNT Catalysts for 4-Nitrophenol Reduction

Carbon nanotubes are arousing real interest in catalysis, either as catalyst support or as catalyst itself. In this work, the influence of CNT doping (O, N, S) on the catalytic performance of CNT and Pd/CNT catalysts have been investigated in the reduction of 4-nitrophenol both under H-2 or using NaBH4 as a hydride source. The morphology, composition, particle size and crystallinity of the materials were investigated by various techniques including HRTEM, STEM, XPS, Raman spectroscopy and XRD. Among the CNT carbocatalysts, only N-CNT is active for 4-nitrophenol reduction at room temperature, and only in the presence of NaBH4. As far as supported Pd catalysts are concerned, the nature of the support influences the Pd nanoparticle location (confinement), the Pd nanoparticles/Pd single atoms ratio and the extent of H-spillover, three catalyst features that directly affect the catalytic activity. The best combination of Pd nanoparticles/Pd single atoms ratio, H-spillover and confinement for 4-nitrophenol reduction using NaBH4, is found in Pd/O-CNT catalysts, while for reactions performed under H-2, Pd/N-CNT presents the best combination.

Automated summary

Carbon nanotubes are of great interest in catalysis, either as catalyst support or catalyst itself. This study investigates the effect of CNT doping (O, N, S) on the catalytic performance of CNT and Pd/CNT catalysts in the reduction of 4-nitrophenol. It is found that only N-doped CNT is active at room temperature in the presence of NaBH4. Furthermore, the nature of the support influences the location, ratio, and extent of H-spillover of Pd nanoparticles, which directly affect the catalytic activity.