ZIF-8 derived carbon (C-ZIF) as a bifunctional electron acceptor and HER cocatalyst for g-C₃N₄: Construction of a metal-free, all carbon-based photocatalytic system for efficient hydrogen evolution

A ZIF-8 derived carbon (C-ZIF)/g-C₃N₄ composite was constructed for the first time through facile thermal condensation of a zeolitic imidazolate framework (ZIF-8) and melamine. The obtained C-ZIF/g-C₃N₄ composite exhibited an obviously enhanced photocatalytic H₂ production rate compared to pure g-C₃N₄ under visible light irradiation. The 1 wt% C-ZIF/g-C₃N₄ composite without loading the Pt co-catalyst showed 36.2 times higher H₂ evolution rate than that of pure g-C₃N₄, which is even 2.8 times higher than that of Pt/g-C₃N₄ (the state-of-the-art g-C₃N₄-based photocatalyst). It was revealed by photoluminescence spectroscopy, time-resolved fluorescence spectroscopy and electrochemical impedance spectroscopy that the formed C-ZIF and g-C₃N₄ junction could promote quick charge carrier separation and transfer. The C-ZIF not only acted as an effective electron acceptor, but also functioned as an efficient hydrogen evolution reaction (HER) cocatalyst to promote photocatalytic hydrogen evolution. Our work provides an effective way for the development of metal-free, all carbon-based photocatalysts for H₂ evolution.