Broadband photocatalysis using a Z-scheme heterojunction of Au/NaYF4:Yb,Er/WO3·0.33H2O-W18O49via a synergetic strategy of upconversion function and plasmonic effect

Abstract

Employing upconversion hosts (which convert lower-energy light into higher-energy light) and plasmonic Au nanoparticles, this work deals with the synthesis of a novel Au/NaYF₄:Yb,Er/WO₃·0.33H₂O-W₁₈O₄₉ {denoted as A/NYYE/WW} heterojunction via a hydrothermal method followed by a photo-reduction method. Also, A/NYYE/WW exhibited the optimum photocatalytic activity and stronger photocatalytic stability for the degradation of nitrobenzene aqueous solution in comparison with a single WO₃·0.33H₂O or NYYE/WW component. Based on the results of X-ray diffraction patterns, field emission electron microscopy, X-ray photoelectron spectra, UV–Vis diffuse reflectance spectra, upconversion luminescence spectra, luminescence decay and photoelectrochemical measurements, it could be considered that a Z-scheme heterojunction was generated over A/NYYE/WW, in which a highly efficient Förster resonant energy transfer from NYYE to WO₃·0.33H₂O-W₁₈O₄₉ was observed and the localized surface plasmon resonance (LSPR) effects of Au NPs and W₁₈O₄₉ could induce the utilization of near infrared light to achieve broadband light absorption. On the other hand, Au NPs also played the role of an electron sink for enhanced charge carrier separation and utilization. Thus, the heterojunction showed the synergetic effects of both upconversion and LSPR features, which could broaden the absorption spectrum to the near infrared region and give rise to a higher yield. It provides a pathway to develop broadband absorption materials in photocatalytic systems.