Mo-Doped/Ni-supported ZnIn2S4-wrapped NiMoO4 S-scheme heterojunction photocatalytic reforming of lignin into hydrogen

Abstract

The photocatalytic reforming of lignin for H₂ evolution can simultaneously overcome environmental and energy issues. However, the photocatalytic activity is still far from useful, considering lignin's complex structure. Therefore, this poses a huge challenge for the design of photocatalysts via ingredient/heterojunction regulation synergistic effects. Herein, in situ Mo-doped and metallic Ni-supported ZnIn₂S₄-wrapped NiMoO₄ step-scheme (S-scheme) heterojunctions (NMO@M–ZIS–N) were developed via a reduction strategy assisted by thermal dissolution. The introduction of NMO can significantly inhibit the agglomeration of ZIS and expose more active sites. The close contact of the two phases helps to form a S-scheme heterojunction, which effectively promotes the separation and transport of photogenerated electron–hole pairs. Due to its unique structural design, the optimal hybrid heterojunction can exhibit excellent photocatalytic hydrogen evolution reaction (HER) activity (5.14 mmol h⁻¹ g⁻¹ for TEOA and 0.53 mmol h⁻¹ g⁻¹ for lignin). The superior photocatalytic performance can be mainly attributed to the synergistic effect of S-scheme heterojunctions coupled with Mo doping and metallic Ni supports to broaden the light absorption, enhance the kinetic process of charge transport, and retain strong redox ability, thereby promoting the photocatalytic HER activity.