Metal-free carbon nanotube-SiC nanowire heterostructures with enhanced photocatalytic H-2 evolution under visible light irradiation

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 H-2 evolution photo-activities 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 H-2 evolution rate among all samples, up to 108 mu mol g(-1) h(-1), which was 3.1 times higher than that of pure SiC without MWCNTs. It suggests that the H-2 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 H-2 generation or environmental pollutant degradation.