Metal-free carbon nanotube–SiC nanowire heterostructures with enhanced photocatalytic H2 evolution under visible light irradiation

Abstract

In this report, metal-free multi-walled carbon nanotube (MWCNT)–SiC nanowire 1D–1D nanoheterostructures were successfully synthesized by an in situ chemical reaction between MWCNTs and silicon powder. A vapor–liquid–solid (VLS) mechanism was found to be responsible for in situ growth of SiC nanowires along MWCNTs. The structure, morphology and composition of the as-obtained MWCNT–SiC 1D–1D samples were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA) and UV-vis absorption spectroscopy. The H₂ evolution photoactivities of the resultant MWCNT–SiC nanoheterostructures under visible light irradiation were also investigated. Results showed that the metal-free MWCNT–SiC 1D–1D nanoheterostructures exhibited the highest H₂ evolution rate among all samples, up to 108 μmol g⁻¹ h⁻¹, which was 3.1 times higher than that of pure SiC without MWCNTs. It suggests that the H₂ evolution activity enhancement of the MWCNT–SiC 1D–1D nanocomposites under visible light irradiation is mainly attributed to the synergistic effects of enhanced separation efficiency of photogenerated hole–electron pairs at the MWCNT–SiC interfaces, improved crystallinity, unique 1D–1D nanoheterostructures and increased visible light absorption. The present work not only gives new insights into the underlying photocatalysis mechanism of the metal-free MWCNT–SiC 1D–1D nanoheterostructures but also provides a versatile strategy to design 1D–1D nanocomposite photocatalysts, with great potential applications in photocatalytic H₂ generation or environmental pollutant degradation.