Ultra-stable dye-sensitized graphene quantum dot as a robust metal-free photocatalyst for hydrogen production

Abstract Covalently attaching a visible light absorbing dye to the graphene quantum dot (GQD) was proven as a viable method to prepare single component metal-free photocatalyst for solar hydrogen production. Despite promising aspects with earlier reported Rhodamine dye attached GQD system, however, quick deterioration of its HER activity within several hours seriously limits its practical application. We have challenged this stability issue by combining the N/S hetero atom doping in GQD structure and molecular structural elaboration of organic dye. By employing 2,3-diaminophenazine (Phz) attached NS-co-doped GQD (Phz-NS_GQD) as a single component photocatalyst in this work, we could demonstrate a dye-sensitized system which sustained over two days without any deterioration (complete linearity up to 50 h was measured) of its HER activity. Higher Apparent Quantum Yield (AQY) values of 49% and 47.7 % at 400, 450 nm wavelength respectively were well supported to its improved catalytic efficiency for H2 production. It was shown that the N,S–co doping and the highly efficient photoinduced electron transfer to GQD core facilitated by phenazine dye are responsible for the improved HER efficiency as well as outstanding photostability.