Ti3C2: An Ideal Co-catalyst?

How 2D Ti3C2 enhances photocatalytic efficiency remains unclear. Now, it is shown that it is graphene quantum dots (GQDs) derived from Ti3C2, rather than 2D Ti3C2 itself, that play the role of co-catalyst for La2Ti2O7/Ti3C2 (LTC) composites during the photocatalytic reaction. After modification of Ti3C2 derivatives, the photocatalytic efficiency of La2Ti2O7 is enhanced 16 times over pure La2Ti2O7. Solid-state NMR, Raman, and HRTEM results confirm the existence of GQDs in Ti3C2 and LTC composites. The GQDs are formed during the chemical change from Ti3AlC2 to Ti3C2 via HF etching, as Ti atoms are removed and unsaturated carbon bonds are left, which react with each other to form sp(2) pi-conjugation GQDs. 2D Ti3C2 is completely oxidized to COx modified TiOx species, causing Ti3C2 to lose its electrical conductivity and the role as co-catalyst. GQDs largely suppress the photogenerated charge recombination of La2Ti2O7, as revealed by the photoluminescence (PL) and transient photocurrent.