Application of single-atom Ti-doped g-C3N4 in photocatalytic H2O2 production

Synthesizing highly effective photocatalysts for hydrogen peroxide (H2O2) generation is still a challenge. In this work, the doping of graphite carbon nitride nanosheets with single-atom titanium, using TiCl3 as a precursor, to form single Ti atom-doped graphitic carbon nitride (Ti-SAC/g-C3N4) photocatalysts can efficiently address this challenge. The photocatalytic activity is enhanced by increasing the concentration of titanium to 0.09%, and subsequently decreases with further increases in the concentration of titanium, thus confirming that the concentration of titanium atoms can modulate the performance of the single-atom catalysts. Furthermore, an in-depth investigation indicates that the bottom of the conduction band (CB) and the maximum of the valence band (VB) can be controlled by varying the concentration of titanium atoms. A high bottom of the CB is beneficial to increase the photocatalytic efficiency. Under acidic conditions and utilizing sacrificial agents, the H2O2 production rate of Ti-C3N4-100 can reach 356.45 μmol L−1 h−1 and is 2.44 and 2.13 times higher than that of BCN and g-C3N4, respectively. The electron spin resonance (ESR) spectra suggest that the generation of superoxide radicals is crucial in the photocatalytic process. This work provides a distinctive strategy to realize single titanium atom doping and offers new insights into structure–property relationships.