Synergy of photon up-conversion and Z-scheme mechanism in graphitic carbon nitride nanoparticles decorated g-C3N4-TiO2

Abstract

Graphitic carbon nitride nanoparticles decorated with g-C3N4-TiO2 composite have been synthesized following hydrothermal method. Synthesis conditions have been optimized to achieve heterogeneous composite photocatalyst resulting in an improved visible-light photocatalytic property. Though surface area significantly decreased for nanoparticles impregnated C3N4-TiO2 (CNCT) in comparison to mesoporous C3N4-TiO2 (CT), CNCT has achieved 4.3-fold higher photocatalytic activity which underscores the dominance of factors other than surface morphology for the increased photocatalytic property in this system. Our results suggest the formation of isotype heterojunction played a crucial role in the delayed recombination of excited electrons. Broad and peak-shifted emission in photoluminescence spectra indicate the existence of n – π* transition that is responsible for the efficient utilization of lower energy photons leading to up-conversion. Transient photocurrent response and electrochemical impedance analysis further substantiate efficient photoresponse and electron transfer properties of C3N4 nanoparticle impregnated mesoporous systems under illumination from UV to IR range. Results demonstrate efficient photocatalytic reduction, specifically showing a significant utility of near IR radiation. We thus gather evidence that carefully engineered novel C3N4-TiO2/C3N4 heterocomposite by morphological and processing conditions augment Z-scheme and help up-conversion resulting in wide wavelength range responsive photocatalysis.