Ti₃C₂: An Ideal Co‐catalyst?

Abstract

How 2D Ti₃ C₂ enhances photocatalytic efficiency remains unclear. Now, it is shown that it is graphene quantum dots (GQDs) derived from Ti₃ C₂ , rather than 2D Ti₃ C₂ itself, that play the role of co-catalyst for La₂ Ti₂ O₇ /Ti₃ C₂ (LTC) composites during the photocatalytic reaction. After modification of Ti₃ C₂ derivatives, the photocatalytic efficiency of La₂ Ti₂ O₇ is enhanced 16 times over pure La₂ Ti₂ O₇ . Solid-state NMR, Raman, and HRTEM results confirm the existence of GQDs in Ti₃ C₂ and LTC composites. The GQDs are formed during the chemical change from Ti₃ AlC₂ to Ti₃ C₂ via HF etching, as Ti atoms are removed and unsaturated carbon bonds are left, which react with each other to form sp² π-conjugation GQDs. 2D Ti₃ C₂ is completely oxidized to CO_x modified TiO_x species, causing Ti₃ C₂ to lose its electrical conductivity and the role as co-catalyst. GQDs largely suppress the photogenerated charge recombination of La₂ Ti₂ O₇ , as revealed by the photoluminescence (PL) and transient photocurrent.