In situ XPS proved effective charge transfer over ZIF-67@CoFe LDH S-scheme heterojunctions for efficient visible light driven hydrogen evolution

A binary catalyst ZIF-67@CoFe LDH with an S-scheme heterojunction mechanism and a framework structure is designed by a physical hybrid process. On the one hand, in situ irradiation X-ray photoelectron spectroscopy analysis showed that the internal electric field drove the photogenerated electrons in ZIF-67 to move towards CoFe LDH, forming an S-scheme heterojunction of ZIF-67@CoFe LDH, which greatly accelerates the separation of photo-generated carriers. On the other hand, the unique framework structure of ZIF-67 provides a large number of aiming points for the CoFe LDH nanorod clusters, effectively preventing the aggregation of CoFe LDH nanorod clusters. When CoFe LDH is aimed at the ZIF-67 surface, the unique 3D/2D structure of ZIF-67@CoFe LDH facilitates the mass transfer properties between ZIF-67 and CoFe LDH and enhances the absorption of visible light. In other words, the unique framework structure of ZIF-67 acts as a “scaffold”, which not only allows for a uniform dispersion of CoFe LDH, but also facilitates a stable loading of CoFe LDH onto the ZIF-67 surface. As a result, the binary catalyst exhibits excellent hydrogen evolution activity and stability. Under 5W (λ ≥ 420 nm) LED illumination, ZCF-15 (586.2 μmol g−1h−1) showed the best hydrogen evolution activity, which is 3.04 times higher than that of ZIF-67 (193 μmol g−1h−1) and CoFe LDH (192.7 μmol g−1h−1), respectively. After 25 h of cycling experiments, ZCF-15 still had 76% of the original amount of hydrogen evolution.