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.
Early transition metals offer promising orthogonal reactivity to catalytic processes promoted by late transition metals. Nevertheless, exploiting variable single-atomic configurations as reactive centers is hitherto not well documented owing to their oxophilic nature. Herein we report an in-situ grafting strategy that employs nitrogenated holey carbon nitrides as a scaffold and invokes the reasonably good match of temperature-dependent pyrolysis to stabilize an atomic titanium–nitrogen (Ti1N2OH) moiety onto the hierarchical porous carbon support (Ti1/NC-SAC). The Ti1/NC-SAC as the cathode in dye-sensitized solar cells assembly exhibited superior electrocatalytic activity toward the triiodine reduction reaction, comparable to the conventional Pt cathode. DFT studies theoretically identified that the intrinsic robust triiodine reduction activity is essentially governed by the unique edge-hosted Ti sites, from both aspects, near-optimal adsorption of I intermediate and electron-donating ability. This work sheds light on the rational design of Ti-based SACs and their applications in photovoltaic fields.
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