Insight into the surface property modification-enhanced C₃N₄ performance of photocatalytic nitrogen fixation

The surface properties of the catalyst have an important influence on the process of heterogeneous reactions. We modified g-C₃N₄ with dicarboxylic acids with different hydrophobicity. Through experiments, we found that the NH₃ yields of modified carbon nitrides can reach 267.89 μmol h^-1 g^-1 when only dissolved nitrogen is involved. But if both dissolved nitrogen and gaseous nitrogen are present in the reaction, the NH₃ yield can reach as high as 751.83 μmol h^-1 g^-1, demonstrating that the participation of dissolved nitrogen alone is not enough and gaseous nitrogen indeed promotes the reaction of photocatalytic nitrogen fixation. Meanwhile, the nitrogen fixation performance of the catalyst is positively correlated with its hydrophobicity, indicating that a reasonable adjustment of the catalysts' hydrophobicity can give them a certain wettability to activate water, while also providing a hydrophobic surface for insoluble gas-phase nitrogen adsorption. This provides new ideas and directions for the design of future heterogeneous reaction catalysts.