Ti3 C2 : An Ideal Co-catalyst?

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 COx modified TiOx 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.