Hydrophobicity-aerophilicity effect boosting efficient CO2 photoreduction in graphitic carbon nitride modified with fluorine-containing groups

Abstract

Inspired by the lotus leaf effect, constructing a hydrophobic surface to endow photocatalysts with underwater aerophilicity, is an effective measure to improve the accessibility of CO2 on the catalyst surface during CO2 photoreduction in the liquid phase. Unfortunately, the aerophilic advantages of the material cannot be fully exploited with the extremely low solubility of CO2 in water. Thus, applying the “hydrophobicity-aerophilicity effect” to gaseous CO2 atmosphere, that is, proving that the hydrophobic material has aerophilic effect in air, has become a challenge. Herein, a hydrophobic graphitic carbon nitride (g-C3N4) photocatalyst modified by CF2 groups (CF2-TCN) is developed to enhance the aerophilicity of the CF2-TCN in air. A theoretical model of the gas-phase “hydrophobicity-aerophilicity effect” and the corresponding theoretical support are presented. Experimental characterizations demonstrate that the grafted CF2 groups create a hydrophobic surface for CF2-TCN, acting as a gas transport layer and enhancing the aerophilicity of CF2-TCN. Theoretical calculations further explain that the strong electronegativity of F atoms in CF2 groups affects the electron cloud distribution of g-C3N4, facilitating the adsorption and activation of CO2 by CF2-TCN. Furthermore, the electron-withdrawing effect of F atoms efficiently extracts electrons, accelerating the intramolecular charge transfer. Benefiting from enhanced aerophilicity and improved electron transfer, the output of CO and CH4 by CF2-TCN are 30.94 and 7.39 μmol·h−1·g−1 without any sacrificial agents, far exceeding that of bulk g-C3N4 (BCN) by 5.54 and 18.95 times, respectively.