Visible-light-driven MWCNT@TiO2 core–shell nanocomposites and the roles of MWCNTs on the surface chemistry, optical properties and reactivity in CO2 photoreduction

Abstract

Multi-walled carbon nanotube (MWCNT)@titanium dioxide (TiO₂) core–shell structures were synthesized through a simple coating approach in this work. Varying the ratio of TiO₂ to MWCNTs revealed the importance of MWCNT loading in controlling the uniformity of the core–shell structures and their photocatalytic performance. These core–shell nanocomposites possessed an excellent visible light absorption with the absorption edge extended into the visible light range of 380–600 nm with respect to the MWCNT loading. The inhibition of electron–hole pair recombination was found to be greater with the increase in the MWCNT loading, revealing that the presence of MWCNTs in the composites enhanced the electron transfer and reduced the electron–hole pair recombination rates. The MWCNT@TiO₂ core–shell nanocomposites exhibited promising photocatalytic activity in carbon dioxide reduction, giving the maximum methane formation of 1.10 μmol g⁻¹-TiO₂ for 8 h of reaction under visible light irradiation at atmospheric temperature and pressure.