The role of hydrogen bonding on enhancement of photocatalytic activity of the acidified graphitic carbon nitride for hydrogen evolution

In this paper, an efficient approach to modify graphitic carbon nitride (g-C3N4) by simple treatment using low-concentration acid under heating was developed. The obtained acidified g-C3N4 sample exhibits about fivefold improvement in the rate of H2 evolution compared to the pristine g-C3N4. The prepared catalysts retained the framework of g-C3N4 but with enhanced separation of photogenerated charge carriers and longer lifetime as well. In addition, according to solid 1H NMR and theoretical calculation, the formed hydrogen bond is enhanced, which can reduce the distance between g-C3N4 and water molecules effectively. The enhanced H-bonding and the formed H-bonding networks are deemed to be the main factors for the improvement of hydrogen evolution.