In situ synthesis of “brick and mortar”-type lignin-derived carbon/TiO2 composite with a remarkable photocatalytic performance

Abstract Alkali lignin (AL), an industrial waste from pulping black liquor, is mainly applied as a low-grade combustible energy source. Design and preparation of high value-added materials with AL is still a challenge. In this work, we firstly introduced ammonium group into AL and prepared quaternized alkali lignin (QAL) for improving the solubility in acidic aqueous solution. Then a facile sol–gel and carbonization process was developed to fabricate lignin-derived carbon/TiO2 (LC/TiO2) composite photocatalyst using QAL as the carbon precursor. The microstructural characteristics and optical property of the LC/TiO2 composite were systematically characterized. Composite exhibited a “brick (TiO2 nanoparticles) and mortar (LC)”-type construction, and TiO2 nanoparticles were coated with LC. The introduction of LC endowed TiO2 with extended photoabsorption region and enhanced separation of photo-generated charge carriers. LC/TiO2 obtained at a carbonization temperature of 650 °C presented the highest photocatalytic activity for the degradation of organic dye, which was about 3.4 times that of bare TiO2. Moreover, LC/TiO2 also presented good recyclability. This facile strategy not only offers great opportunities for the high value-added application of industrial lignin, but also promotes the practical application of TiO2 photocatalyst.