Harnessing the Synergistic Power of Ce₂S₃/TiO₂ S-Scheme Heterojunctions for Profound C–O Bond Cleavage in Lignin Model Compounds

Abstract

In the context of achieving carbon neutrality, converting lignin-derived molecules into high-value products through photocatalytic technology provides an environmentally friendly pathway. Establishing energy-efficient processes for converting lignin derivatives requires the construction of highly active and selective photocatalysts. However, enhancing the efficiency and selectivity of photocatalysts for lignin degradation poses an ongoing challenge due to discrepancies in the redox potential and the rapid recombination of photogenerated carriers. To address these significant obstacles, we devised an innovative strategy by developing a Ce 2 S 3 nanoparticle-anchored TiO 2 nanorod (Ce 2 S 3 /TiO 2 ). This advanced photocatalyst with the S-scheme heterojunction, enabling simultaneous control of carrier dynamics and band structure, was used to study the photocatalytic degradation of the lignin model compound 2phenoxy-1-acetophenone. Moreover, the photocatalyst can cleave the C β -O-4 bond selectively to convert the lignin model compound 2-phenoxy-1-acetophenone into phenol and acetophenone under visiblelight irradiation. The yields are up to 94 and 80%, respectively, and 94 or 1.4 times greater than those obtained by pure TiO 2 or Ce 2 S 3 individually. In addition, our study for the increased activity in Ce 2 S 3 /TiO 2 based on density functional theory calculations emphasizes the pivotal role of the S-scheme heterojunction generated between Ce 2 S 3 and TiO 2 . This heterojunction significantly enhances carrier separation efficiency, thereby augmenting the efficacy of the photocatalytic process. The findings furnish valuable insights for developing advanced photocatalytic systems tailored to the efficient depolymerization of C β -O-4 bonds in lignin.

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

“…Among various ongoing research activities, lignin conversion is achieved via different techniques, i.e., thermal catalytic, photocatalytic, and electrocatalytic. [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44] The traditional lignin depolymerization reaction is carried out by various thermochemical and catalytic techniques like acid/base hydrolysis, pyrolysis, oxidation, reduction, and hydrogenation. [35][36][37][38][39][40][41][42][43][44] However, these reactions are accompanied by intense reaction conditions that put a lot of strain on machinery and its operations, require a lot of energy, and bring harm to the environment.…”

“…Furthermore, these dopant and defective sites provide an active surface for the oxidant or reductant to be adsorbed properly and successively undergo the redox process. 29,[79][80][81] So, the efficiency of lignin conversion activity of a general approach, i.e., metal doping and loading TiO 2 , has also been investigated. For example, Song et al 79 prepared 1D TiO 2 nanostructures decorated with rare earth ions (La 3+ , Ce 3+ , Pr 3+ , Sm 3+ , Eu 3+ ,Tb 3+ , and Er 3+ ) by a two-step reaction.…”

“…Furthermore, these dopant and defective sites provide an active surface for the oxidant or reductant to be adsorbed properly and successively undergo the redox process. 29,79–81…”

“…Liao et al 29 prepared a metal sulfide-TiO 2 heterostructure by combining Ce 2 S 3 with TiO 2 . The exquisite coral shape of TiO 2 nanorods loaded with spherical Ce 2 S 3 nanoparticles was observed, as illustrated in Fig.…”