Two-electron transfer mechanism from 3D/3D nickel selenide/MoS2 heterostructure accelerates photocatalytic hydrogen evolution and tetracycline hydrochloride removal

Establishing highly effective charge transfer channels and providing adequate active sites for improving the activity of photocatalyst is still a challenging issue. Herein, a novel marigold-like NiSe2/MoS2 hierarchical heterostructure is firstly reported via in situ deposition of mesoscale hedgehog NiSe2 nanoparticles on the nanosheet edge of MoS2 flowerspheres. The optimal 5.4% NiSe2/MoS2 composite exhibits moderate hydrogen evolution rate of 2473.7 μmol·h−1·g−1 without any noble metal cocatalysts and achieves mineralization capacity for tetracycline hydrochloride (58.1%) after 120 min, respectively. The transfer pathway of photogenerated charge carriers, the generation process and function of different reactive oxygen species (·O2–, ·OH, 1O2 and H2O2) are detailedly discussed. Based on the results of various characterizations and DFT calculations, the improvement of photocatalytic performance could be derived from the unique morphology effect with numerous reactive sites and extended light harvesting ability, as well as the type-II heterojunction with promoted photocarriers separation efficiency and lower interfacial migration impedance, which arose from a continuous two-step/two-electron reduction pathway. The developed synthetic strategy may provide new inspirations for the rational design and construction of high efficiency photocatalysts with hierarchical structures for energy conversion and water environment remediation.