Highly luminescent nitrogen doped graphene quantum dots sensitized TiO2 nanorod arrays for enhanced photoelectrochemical performance

Abstract

Photoelectrochemical (PEC) properties of N doped graphene quantum dots (NGQDs) sensitized TiO2 nanorods (NRs) have been studied. NGQDs have been prepared by using a facile and low temperature solvothermal process. TiO2 NRs have been grown on fluorine doped tin oxide (FTO) coated glass substrate using hydrothermal method. The microstructure, chemical bonding and optical properties of the NGQDs have been investigated in details. The NGQDs are highly crystalline with an average diameter of ~8 nm and demonstrate excellent excitation dependent photoluminescence (PL). The PEC properties of TiO2 NRAs have been studied after attachment of NGQDs at different loading times and optimum performance has been obtained at one hour. The photoresponse and PEC performance of TiO2 NRs have been boosted significantly after the attachment of NGQDs. The photoconversion efficiency (η%) and incident photon-to-current conversion efficiency (IPCE) of NGQDs sensitized TiO2 NRs has been improved by 85.3% and 89.4%, respectively compared to pristine TiO2 NRs. The charge transfer resistance (Rct) at nanorods/electrolyte junction has been decreased by 56.5% compared to pristine nanorods under white light illumination. In this study, the role of NGQDs as a green photosensitizer with TiO2 NRAs has been explored in detail.