In-Situ Grafting of Single-Atomic Titanium-Nitrogen Moiety onto Carbon Nanostructures for Efficient Photovoltaic Devices

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.