Controlled high-density interface engineering of Fe3O4-FeS nanoarray for efficient hydrogen evolution

The rational design of double active sites system is vital for constructing high-efficiency iron sulfides electrocatalysts towards hydrogen evolution reaction (HER) in alkaline media. However, it remains a challenge to controllably create the high-density interface of double sites for optimal synergistic effect. Herein, we reported a simple chemical oxidation-induced surface reconfiguration strategy to obtain the interface-rich Fe3O4-FeS nanoarray supported on iron foam (Fe3O4-FeS/IF) using FeS nanosheets as precursors. The abundant Fe3O4-FeS interfaces could improve the dispersion of active sites and facilitate the electron transfer, leading to enhanced hydrogen evolution efficiency. And meanwhile, by altering the oxidation temperature, the content of S and O could be effectively controlled, further achieving the ratio optimization of Fe3O4 to FeS. Synchrotron-based X-ray absorption near-edge structure, X-ray photoelectron spectroscopy and ultraviolet photoemission spectroscopy consistently confirm the changes of electronic structure and d-band center of Fe3O4-FeS after chemical oxidation. Consequently, Fe3O4-FeS/IF exhibits excellent alkaline HER activity with a low overpotential of 120.8 mV to reach 20 mA cm−2, and remains stable ranging from 10, 20 to 50 mA cm−2 for each 20 h, respectively. Therefore, the facile and controllable chemical oxidation may be an effective strategy for designing high-density interfaces of transition metal-based sulfides towards alkaline HER.