Path of electron transfer created in S-doped NH2-UiO-66 bridged ZnIn2S4/MoS2 nanosheet heterostructure for boosting photocatalytic hydrogen evolution

Abstract

Developing well-designed architectures plays a decisive role in accelerating photo-generated carrier transport in composite photocatalysts. Herein, a microporous sulfur-doped (S-doped) NH₂-UiO-66 bridged ZnIn₂S₄/MoS₂ sheet heterostructure photocatalyst is synthesized through thermolysis of sulfur rich precursors to functionalize the organic ligands of NH₂-UiO-66 to boost photocatalytic efficiency. XPS spectra confirm the existence of S-doped NH₂-UiO-66, and Raman spectra show transition metal-assisted sulfuration instead of carbonization. FT-IR spectra further confirm the formation of Zn–O–C covalent bonds at the interface between NH₂-UiO-66 and ZnIn₂S₄. In particular, the Zn–O–C bonds preserve the energy of photo-generated electrons and inhibit the energy relaxation of electrons at the interface of the heterostructure. In addition, NH₂-UiO-66 with a high photocatalytic response greatly facilitates the transport of photo-generated electrons not only as an electron transport bridge but also as an electron donor. Profiting from the unique design of the ternary composite, the sample exhibits excellent PHE performance. The obtained ZnIn₂S₄/NH₂-UiO-66/5%-MoS₂ (5.69 mmol h⁻¹ g⁻¹) exhibits the highest H₂ evolution rate, which is 15 and 1.9 times higher than those of ZnIn₂S₄ (0.369 mmol h⁻¹ g⁻¹) and 5%-MoS₂/ZnIn₂S₄ (2.93 mmol h⁻¹ g⁻¹), respectively. In addition, the apparent quantum efficiency of the ZnIn₂S₄/NH₂-UiO-66/5%-MoS₂ composite (7.95%) is higher than that of the 5%-MoS₂/ZnIn₂S₄ composite (3.12%) at 420 nm. This work provides new insight into designing novel and highly efficient photocatalysts for photocatalytic hydrogen evolution.