Revolutionizing lignin photovalorization: recent advances in TiO2-based materials and beyond in pursuit of optimal solutions for a sustainable future

Abstract

Lignin, an underutilized lignocellulosic component of biomass and often called waste, is a rich reservoir of fuel and aromatic chemicals. Although there has been a lot of research in lignin chemistry in recent years, completely realizing the ability of lignin is still a long way off. The photocatalytic lignin valorization process has attracted much attention for producing highly expensive bulk and fine chemicals by using renewable solar light and inexpensive lignin. Hence, to cover the most recent trend, the advancement of TiO₂-based photocatalysts and other alternative catalysts for the application of lignin valorization is discussed here. The objective of this review is to uncover how catalyst properties like physical features, band gap, crystallinity, defects, morphology, etc., and the experimental setup nature of the reactant, solvent, light intensity, reaction temperature, pressure, etc. with the latest state of the art are impacting the lignin photoconversion process in terms of product yield and selectivity. Furthermore, the latest pathways for the photoconversion process and the mechanisms involved are also briefly discussed. In the closing remarks, a succinct segment describes every roadblock that will arise in the process of upgrading lignin into valuable chemicals and the means of improvement.