Graphene nanoribbon-TiO2-quantum dots hybrid photoanode to boost the performance of photoelectrochemical for hydrogen generation

We report the effect of incorporation of graphene nanoribbons (GNR) into a TiO2 mesoporous film sensitized with colloidal CdSe/CdS core/shell quantum dots (QDs) on the efficiency and long-term stability of a photoelectrochemical (PEC) cell for hydrogen (H2) generation. The GNR-TiO2 hybrid photoanodes were prepared by using simple, low-cost and large-area scalable doctor-blade method. The presence of GNR in the hybrid photoanode was confirmed by ultraviolet-visible absorption measurements, scanning electron microscopy and Raman spectroscopy. Our results demonstrate that an optimum loading of 0.02 wt% GNR increases the photocurrent density (at 0.8 V vs RHE) of the PEC device up to 5.51 mA/cm2, which is 30% higher than that of the control device. This improvement in photocurrent density can be attributed to enhanced electron transport (reduced charge transport resistance) in GNR-TiO2 hybrid anodes as confirmed by electrochemical impedance spectroscopy. In addition, PEC cells based on GNRs-TiO2/QDs hybrid photoanode maintain ∼65% of the initial photocurrent density after 7200 s of continuous one sun illumination, which is 15% higher than PEC cell based on a standard TiO2/QDs photoanode. Our findings offer a simple, large area scalable and low-cost approach to fabricate photoanode for high-performance optoelectronic devices, such as improving the performance of PEC cells for hydrogen generation.