Showing papers on "Photocatalysis published in 2023"

Construction of Ag2CO3/BiOBr/CdS ternary composite photocatalyst with improved visible-light photocatalytic activity on tetracycline molecule degradation.

Abstract: Photocatalytic degradation was considered as a best strategy for the removal of antibiotic drug pollutants from wastewater. The photocatalyst of ABC (Ag2CO3/BiOBr/CdS) composite synthesized by hydrothermal and precipitation method. The ABC composite used to investigate the degradation activity of tetracycline (TC) under visible light irradiation. The physicochemical characterization methods (e.g. scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution-transmission electron microscopy (HR-TEM), ultraviolet visible spectroscopy (UV), photoluminescence (PL) and time resolved photoluminescence (TRPL) clearly indicate that the composite has been construct successfully that enhances the widened visible light absorption, induces charge transfer and separation efficiency of electron – hole pairs. The photocatalytic activity of all samples was examined through photodegradation of tetracycline in aqueous medium. The photocatalytic degradation rate of ABC catalyst could eliminate 98.79% of TC in 70 min, which is about 1.5 times that of Ag2CO3, 1.28 times that of BiOBr and 1.1 times that of BC catalyst, respectively. The role of operation parameters like, TC concentration, catalyst dosage and initial pH on TC degradation activity were studied. Quenching experiment was demonstrated that ·OH and O2·− were played a key role during the photocatalysis process that was evidently proved in electron paramagnetic resonance (EPR) experiment. In addition, the catalyst showed good activity perceived in reusability and stability test due to the synergistic effect between its components. The mechanism of degradation of TC in ABC composite was proposed based on the detailed analysis. The current study will give an efficient and recyclable photocatalyst for antibiotic aqueous pollutant removal.

Modulating Uranium Extraction Performance of Multivariate Covalent Organic Frameworks through Donor–Acceptor Linkers and Amidoxime Nanotraps

Abstract: Covalent organic frameworks (COFs) can be designed to allow uranium extraction from seawater by incorporating photocatalytic linkers. However, often sacrificial reagents are required for separating photogenerated charges which limits their practical applications. Herein, we present a COF-based adsorption-photocatalysis strategy for selective removal of uranyl from seawater in the absence of sacrificial reagents. A series of ternary and quaternary COFs were synthesized containing the electron-rich linker 2,4,6-triformylphloroglucinol as the electron donor, the electron-deficient linker 4,4′-(thiazolo[5,4-d]thiazole-2,5-diyl)dibenzaldehyde as the acceptor, and amidoxime nanotraps for selective uranyl capture (with the quaternary COFs incorporating [2,2′-bipyridine-5,5′-diamine-Ru(Bp)2]Cl2 as a secondary photosensitizer). The ordered porous structure of the quaternary COFs ensured efficient mass transfer during the adsorption-photocatalysis capture of uranium from seawater samples, with photocatalytically generated electrons resulting in the reduction of adsorbed U(VI) to U(IV) in the form of UO2. A quaternary COF, denoted as COF 2-Ru-AO, possessed a high uranium uptake capacity of 2.45 mg/g/day in natural seawater and good anti-biofouling abilities, surpassing most adsorbents thus far. This work shows that multivariate COF adsorption-photocatalysts can be rationally engineered to work efficiently and stably without sacrificial electron donors, thus opening the pathway for the economic and efficient extraction of uranium from the earth’s oceans.

Tuning excited state electronic structure and charge transport in covalent organic frameworks for enhanced photocatalytic performance

Abstract: Abstract Covalent organic frameworks (COFs) represent an emerging class of organic photocatalysts. However, their complicated structures lead to indeterminacy about photocatalytic active sites and reaction mechanisms. Herein, we use reticular chemistry to construct a family of isoreticular crystalline hydrazide-based COF photocatalysts, with the optoelectronic properties and local pore characteristics of the COFs modulated using different linkers. The excited state electronic distribution and transport pathways in the COFs are probed using a host of experimental methods and theoretical calculations at a molecular level. One of our developed COFs (denoted as COF-4) exhibits a remarkable excited state electron utilization efficiency and charge transfer properties, achieving a record-high photocatalytic uranium extraction performance of ~6.84 mg/g/day in natural seawater among all techniques reported so far. This study brings a new understanding about the operation of COF-based photocatalysts, guiding the design of improved COF photocatalysts for many applications.

Visible light activated MoS2/ZnO composites for photocatalytic degradation of ciprofloxacin antibiotic and hydrogen production

Abstract: In the photocatalysis process, photon energy is mainly converted into chemical energy with the help of both light and catalyst. This process can be used in different applications like photocatalytic degradation of hazardous compounds, fixation of nitrogen, hydrogen production, air purification, water splitting, carbon dioxide reduction etc. In this research work, multiplicative ZnO and MoS2/ZnO (MZ) composites were synthesized using green chemical methods like the hydrothermal process and used in two different applications i) photocatalytic degradation of ciprofloxacin (CIP) antibiotic and ii) hydrogen production. CIP is not easily biodegradable and is mainly used in various antibacterial treatments. The photocatalytic activity was tested for ZnO and different MoS2/ZnO composites along with this the effect of different amounts of catalysts doses was studied. MoS2/ZnO composites exhibit superior photocatalytic performance than ZnO for photocatalytic degradation of CIP. Using the LC-MS technique possible degradation pathways are proposed. The same photocatalyst materials were used to test the photocatalytic H2 production activity. H2 production rates were found to be 22, 39 and 235 µmol/g/h for ZnO, MoS2 and MZ-30 composite respectively. Superior photocatalytic activity of MZ-30 composite than ZnO is chiefly attributed to the extended light absorption capacity, effective charge transfer, suitable band alignment between the ZnO and MoS2, minimum recombination of charge carriers etc.

The Collision between g-C3 N4 and QDs in the Fields of Energy and Environment: Synergistic Effects for Efficient Photocatalysis.

Abstract: Recently, graphitic carbon nitride (g-C3 N4 ) has attracted increasing interest due to its visible light absorption, suitable energy band structure, and excellent stability. However, low specific surface area, finite visible light response range (<460 nm), and rapid photogenerated electron-hole (e- -h+ ) pairs recombination of the pristine g-C3 N4 limit its practical applications. The small size of quantum dots (QDs) endows the properties of abundant active sites, wide absorption spectrum, and adjustable bandgap, but inevitable aggregation. Studies have confirmed that the integration of g-C3 N4 and QDs not only overcomes these limitations of individual component, but also successfully inherits each advantage. Encouraged by these advantages, the synthetic strategies and the fundamental of QDs/g-C3 N4 composites are briefly elaborated in this review. Particularly, the synergistic effects of QDs/g-C3 N4 composites are analyzed comprehensively, including the enhancement of the photocatalytic performance and the avoidance of aggregation. Then, the photocatalytic applications of QDs/g-C3 N4 composites in the fields of environment and energy are described and further combined with DFT calculation to further reveal the reaction mechanisms. Moreover, the stability and reusability of QDs/g-C3 N4 composites are analyzed. Finally, the future development of these composites and the solution of existing problems are prospected.

Recent advances in electrocatalysts for seawater splitting

Abstract: Abstract Water splitting is an effective strategy to produce renewable and sustainable hydrogen energy. Especially, seawater splitting, avoiding use of the limited freshwater resource, is more intriguing. Nowadays, electrocatalysts explored for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) using natural seawater or saline electrolyte have been increasingly reported. To better understand the current status and challenges of the electrocatalysts for HER and OER from seawater, we comprehensively review the recent advances in electrocatalysts for seawater splitting. The fundamentals, challenges and possible strategies for seawater splitting are firstly presented. Then, the recently reported electrocatalysts that explored for HER and OER from seawater are summarized and discussed. Finally, the perspectives in the development of high-efficient electrocatalysts for seawater splitting are also proposed.