Abstract
In the present study, alkaline earth metal scheelite-type ABO4 compounds (A = Ca, Sr, and Ba; B = Mo and W) synthesized by a hydrothermal method were systematically studied. The as-obtained photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) surface area analysis, UV–vis diffuse reflectance (DR/UV–vis) spectroscopy, photoluminescence, and thermoluminescence (TL) spectroscopy together with charge carrier lifetime measurements, electron paramagnetic resonance (EPR) spectroscopy, and electrochemical impedance spectroscopy (EIS). The photocatalytic activity was studied in the reaction of phenol degradation under simulated solar light. The obtained tungstates and molybdates revealed excellent photocatalytic activity despite the low surface area and wide bandgap typical for insulators. The mechanism of phenol degradation proceeded through hydroquinone and catechol formation in the presence of hydroxyl and superoxide radicals. The presence of electron traps allowed absorption of light with lower energy than resulting from the absorption edge. BaWO4 and SrWO4, with the most extended average carrier lifetime, were the most efficient photocatalysts from the obtained series. In general, molybdates exhibited lower photocatalytic activity toward phenol degradation due to deeper trap states and lower average charge carrier lifetimes than tungstates. Additionally, electrochemical studies demonstrated that molybdates exhibit more insulating behavior than tungstates. The overall results showed that wide-bandgap semiconductors, mainly tungstates, can be applied as earth-abundant photocatalytic materials for the degradation of persistent organic pollutants.
Highlights
The environmental pollution due to increased agricultural, industrial, and domestic activities has led to the global need to develop advanced and more effective water treatment technologies
Heterogeneous photocatalysis belonging to the group of advanced oxidation processes (AOPs) has been demonstrated as a green technology for removing toxic contaminants and energy production
The charge carrier lifetime was the crucial factor influencing the photocatalytic performance of the as-synthesized materials
Summary
The environmental pollution due to increased agricultural, industrial, and domestic activities has led to the global need to develop advanced and more effective water treatment technologies. The main advantage is the possibility of light-induced degradation of the broad spectrum of recalcitrant organic pollutants.[1−5] The most frequently studied photocatalysts include oxides, sulfides, selenides, and iodides as single and hybrid compounds.[6] the ability to apply heterogeneous photocatalysis in wastewater treatment at a full technological scale requires the application of earth-abundant photocatalytic materials, whose preparation method will not be expensive or sophisticated.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
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 call
