Insights into Photothermally Enhanced Photocatalytic U(VI) Extraction by a Step-Scheme Heterojunction

Abstract

In this work, a CdS/BiVO4 step-scheme (S-scheme) heterojunction with self-photothermally enhanced photocatalytic effect was synthesized and applied for efficient U(VI) photoextraction. Characterizations such as transient absorption spectroscopy and Tafel test together confirmed the formation of S-scheme heterojunctions, which allows CdS/BiVO4 to avoid photocorrosion while retaining the strong reducing capacity of CdS and the oxidizing capacity of BiVO4. Experimental results such as radical quenching experiments and electron spin resonance show that U(VI) is rapidly oxidized by photoholes/•OH to insoluble UO2(OH)2 after being reduced to U(IV) by photoelectrons/•O2-, which precisely avoids the depletion of electron sacrificial agents. The rapid recombination of electron-hole pairs triggered by the S-scheme heterojunction is found to release large amounts of heat and accelerate the photocatalysis. This work offers a new enhanced strategy for photocatalytic uranium extraction and presents a direction for the design and development of new photocatalysts.

Dipole Moment and Built-In Polarization Electric Field Induced by Oxygen Vacancies in BiOX for Boosting Piezoelectric–Photocatalytic Removal of Uranium(VI)

“…The XPS complete spectrum in Figure g demonstrates that there are unmistakably U 4f peaks following the photocatalyst. Also, from the XPS fine spectra of uranium after the reaction (Figure h), it can be seen that the binding energies of 381.3 and 392.3 eV are the characteristic peaks of U(VI), and, notably, the binding energies of 380.6 and 390.1 eV correspond to the characteristic peaks of U(IV), − indicating that OVs-BiOBr-30 successfully reduced U(VI) to U(IV) after 60 min of piezoelectric–photocatalysis. The Raman spectroscopy of the reaction OVs-BiOBr-30 (Figure i) revealed that it has a weak characteristic peak at a wavelength of 821 cm –1 , which is associated with uranium peroxide dihydrate [(UO 2 )O 2 ·2H 2 O].…”

Emergence of Non‐photoresponsive Catalytic Techniques for Environmental Remediation and Energy Generation

“…Both temperature‐dependent catalysts fall within the category of thermal catalysts and may be superior to one another under certain circumstances. The degradation of water contaminants, air purification, water disinfection, and water splitting for hydrogen production and carbon dioxide abatement are some of the potential applications that have been thought of thus far [135,138,139] . In this section, we discuss the mechanisms of thermocatalysis and pyrocatalysis with their potential applications.…”

Highly Selective Extraction of U(VI) from Solutions by Metal Organic Framework-Based Nanomaterials through Sorption, Photochemistry, and Electrochemistry Strategies

“…Under alternating magnetic field, the piezocatalytic materials could produce ·OH, ·O 2 – , etc., which are active to reduce U­(VI) to solid U­(IV). Zhang et al found that U­(VI) could be reduced to form UO 2 (OH) 2 precipitates by ·OH and ·O 2 – radicals. Because the magnetic field was easily obtained, the piezocatalytic elimination of U­(VI) or other metals could be achieved easily.…”