Atomically Dispersed Nickel (Ni) Species on Black TiO₂-O_v Photocatalysts Derived from Ti₃C₂T_x (MXene)

Production efficiency of solar-driven hydrogen (H₂) through water splitting relies strongly on the activity and stability of semiconductor photocatalysts. Black TiO₂ semiconductors have shown specific promise for photocatalysis due to their enhanced solar light absorption by the formation of oxygen vacancies and Ti³⁺ species, but their fabrication and functionalization are very challenging. Herein, we report the synthesis of Ti₃C₂T_x (MXene)-derived black TiO₂ with atomically anchored nickel (Ni) species for the photocatalytic hydrogen evolution reaction. Advanced characterization techniques such as X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and high-resolution transmission electron microscopy verified the presence of Ni-O bonds, confirming that the Ni atoms are coordinated with the surrounding O atoms from anatase black TiO₂ with oxygen vacancies (TiO₂-O_v). The introduction of atomic Ni species onto black TiO₂-O_v promoted the separation of photogenerated charge carriers, thus leading to a significant enhancement in photocatalytic H₂ production. Specifically, our Ni-TiO₂-O_v delivered a H₂ production rate of 697.44 μmol g^-1 h^-1 under 365 nm light-emitting diode light, which is 3.7 times higher than that of the system with bare black TiO₂-O_v. This work paves the way to the design of functional black TiO₂ materials using a facile and low-cost strategy.