Zinc-Indium Sulfide Nanosheets with Anion Vacancies Promote Photocatalytic Upgrading of Lignin Oil to Biodiesel

Abstract

The escalating global energy crisis and environmental degradation have intensified the demand for sustainable and renewable energy solutions, positioning lignin oil as a promising biofuel precursor. Here, we report the photocatalytic upgrading of lignin oil to biodiesel precursors by modulating morphology and sulfur vacancies in zinc-indium sulfide (ZIS) catalysts, thereby promoting the concerted proton-electron transfer (CPET) process. The results show that sulfur vacancies are pivotal for enhancing charge separation, thereby improving photocatalytic efficiency. ZIS nanosheets with an optimized vacancy concentration (ZIS-NS-8) delivered diesel-like dimers in 93% yield with 99% selectivity under visible-light irradiation, accompanied by H₂ evolution, a sixfold activity improvement over unoptimized ZIS. Moreover, the approach efficiently upgrades real lignin-oil feedstocks to biodiesel precursors in 90% conversion. By elucidating how ZIS morphology and sulfurvacancy concentration govern catalytic efficiency, this work underscores the central role of vacancy engineering in boosting ZIS photocatalysis and provides a promising route for transforming lignin oil into value-added biodiesel intermediates, informing the design of efficient catalysts for renewable-energy applications.