Solar Hydrogen Generation over Carbon Nitride Photocatalyst Promoted by Water‐Soluble Carbon Dots

Abstract Solar hydrogen generation from water is one of the promising routes to alleviate the current environmental and energy issues. Graphitic carbon nitride (g‐C 3 N 4 ) has emerged as a promising photocatalyst for hydrogen evolution using visible light while withstanding harsh chemical environments. However, the high occurrence of trapped unreactive charges seriously affects the catalytic performance of g‐C 3 N 4 in photocatalysis applications. Herein, we show that the addition of water‐soluble carbon dots (CDs) to the reaction solution will promote the relaxation of photogenerated electrons in g‐C 3 N 4 , thus effectively improving the photocatalytic performance for hydrogen evolution by two times (983.7 vs. 490.7 μmol ⋅ h −1 ⋅ g −1 for with and without CDs, respectively). The steady state properties of the reaction system are studied by ultraviolet‐visible (UV‐vis) and photoluminescence (PL) excitation/emission spectroscopy, which show that the introduction of CDs enhances the visible light absorption of the reaction system. Furthermore, the charge trapping and detrapping processes in g‐C 3 N 4 are further revealed by using time‐resolved photoluminescence (tr‐PL) spectroscopy. The correlation between charge transfer and photocatalytic activity provides new insights into the charge separation dynamics and activity of carbon‐based photocatalysts.