Abstract
Photonic crystal structuring has emerged as an advanced method to enhance solar light harvesting by metal oxide photocatalysts along with rational compositional modifications of the materials’ properties. In this work, surface functionalization of TiO2 photonic crystals by blue luminescent graphene quantum dots (GQDs), n–π* band at ca. 350 nm, is demonstrated as a facile, environmental benign method to promote photocatalytic activity by the combination of slow photon-assisted light trapping with GQD-TiO2 interfacial electron transfer. TiO2 inverse opal films fabricated by the co-assembly of polymer colloidal spheres with a hydrolyzed titania precursor were post-modified by impregnation in aqueous GQDs suspension without any structural distortion. Photonic band gap engineering by varying the inverse opal macropore size resulted in selective performance enhancement for both salicylic acid photocatalytic degradation and photocurrent generation under UV–VIS and visible light, when red-edge slow photons overlapped with the composite’s absorption edge, whereas stop band reflection was attenuated by the strong UVA absorbance of the GQD-TiO2 photonic films. Photoelectrochemical and photoluminescence measurements indicated that the observed improvement, which surpassed similarly modified benchmark mesoporous P25 TiO2 films, was further assisted by GQDs electron acceptor action and visible light activation to a lesser extent, leading to highly efficient photocatalytic films.
Highlights
Structural engineering of semiconductor photocatalysts in the form of photonic crystals (PCs) has been attracting particular attention as an advanced approach to improve solar light harvesting, especially at the absorption edge of wide band gap metal oxides such as titania [1,2]
Surface modification of TiO2 photonic crystals in the form of anatase inverse opals has been implemented by impregnation in aqueous suspension of coal-derived, blue luminescent graphene quantum dots (GQDs) with n–π * absorption band at about 350 nm
photonic band gap (PBG) engineering of the co-assembled inverse opal films to the GQDs-TiO2 composite’s absorption edge resulted in distinct improvements of the salicylic acid (SA) photocatalytic degradation and photocurrent density under UV–VIS and visible light illumination, outperforming benchmark mesoporous GQD-P25 films subjected to the same treatment
Summary
Structural engineering of semiconductor photocatalysts in the form of photonic crystals (PCs) has been attracting particular attention as an advanced approach to improve solar light harvesting, especially at the absorption edge of wide band gap metal oxides such as titania [1,2]. Tuning the PBG or stop band (in the case of incomplete PBG) position, which is determined by the inverse opal periodicity, enables overlap of the red- (long-wavelength) or blue-edge (short-wavelength) slow photons of the fundamental bandgap or preferentially higher order slow-light modes [5] with catalyst’s target spectral regions of weak electronic absorbance. This resonance effect can selectively enhance light absorbance at these wavelengths and effectively extend the path length for incident photons promoting photocarrier generation, provided that detrimental stop band (Bragg) reflection losses are moderated. The macroporous structure of inverse opals along with the secondary mesoporosity of the nanocrystalline inorganic skeleton offers a porous network of interconnected macro-mesopores [6], which facilitate molecular diffusion and increase the amount of adsorption and reaction sites that are key aspects for the photocatalytic process
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
