In Situ Construction of Globe‐like Carbon Nitride as a Self‐Cocatalyst Modified Tree‐like Carbon Nitride for Drastic Improvement in Visible‐Light Photocatalytic Hydrogen Evolution

Abstract

AbstractPhotogenerated carriers possess high recombination efficiency in carbon–nitrogen materials, which results in lower photocatalytic H2 evolution activity. By reviewing the literature, it was concluded that relying only on a structure‐controlled technique was insufficient to reduce the combination of photogenerated carriers without introducing a foreign material or element. Hence, bulk‐like g‐C3N4 [CN (B)], globe/strip‐like g‐C3N4 [CN (G/S)], and globe/tree‐like g‐C3N4 [CN (G/T)] were in situ obtained through a facile calcination method. Similar to platinum (Pt) as a cocatalyst, globe‐like carbon nitride as a self‐cocatalyst was found to improve the separation efficiency of photogenerated carriers effectively. Interestingly, the hollow‐tree‐branch morphology of CN (G/T) effectively transmitted photogenerated holes, which thereby enhanced the photocatalytic H2 evolution activity. The H2 production rates of CN (G/S) and CN (G/T) were almost 10.7 and 18.3 times greater, respectively, than that of CN (B) without the addition of Pt as a cocatalyst. Notably, CN (G/S) and CN (G/T) displayed considerable rates of H2 production in water relative to that shown by CN (B) (no activity) without the use of any sacrificial agent and by using Pt as a cocatalyst. CN (G/T) showed outstanding long‐term stability, as evidenced by seven cycle tests performed over 28 h. The charge separation and transfer process of the compounds were verified by photoluminescence (PL), time‐resolved PL spectroscopy, and photocurrent measurements.