High-efficient precious-metal-free g-C3N4-Fe3O4/β-FeOOH photocatalyst based on double-heterojunction for visible-light-driven hydrogen evolution

The two-dimensional (2D) g-C 3 N 4 has a wide application prospect in photocatalysis field due to its larger surface reactions, wider absorption of light and faster charge separation. However, the lack of active site of reduction leads to its poor hydrogen evolution reaction (HER) activity. In this work, the intermediate β-FeOOH was synthesized as a high-efficiency precious metal free co-catalyst in hydrogen production. Then, the g-C 3 N 4 -Fe 3 O 4 /β-FeOOH (CNFF-x,y, x = 1, 2 and 3, y denotes the reaction time (h)) photocatalyst based on p-n and Z-scheme heterojunction was constructed via a subsequent solvothermal process. The chemical composition, microtopography, crystallography, photochemical and electrochemical properties of the CNFF-x,y were analyzed by XRD, FI-IR, TEM, XPS and so on. The visible-light-driven (VLD) catalytic performance of CNFF-x,y heterojunction was evaluated by the hydrogen evolution reaction (HER). Results showed that CNFF-2,10 photocatalyst based on p-n (g-C 3 N 4 -Fe 3 O 4 ) and Z-scheme (Fe 3 O 4 /β-FeOOH) heterojunction presented the highest VLD catalytic HER activity (33.25 μmol g −1  h −1 ) at the absence of Pt co-catalyst after illumination for 6 h. It indicated that the effective introduction of Fe 3 O 4 /β-FeOOH nanoparticles (NPs) into g-C 3 N 4 to construct double-heterojunction (g-C 3 N 4 -Fe 3 O 4 /β-FeOOH) could greatly broaden the light response property and inhibit the recombination of photo-induced carriers, exhibiting enhanced HER activity. Meanwhile, this double-heterojunction photocatalyst presented robust photostability and reproducibility even been used several times. The findings of an intermediate β-FeOOH were put forward in this study will provide some new ideas for the research of HER.