Yuanyuan Li,Xiaofang Tian,Yaoqiong Wang,Qimei Yang,Yue Diao,Bin Zhang,Dingfeng Yang
Using solar energy to remove antibiotics from aqueous environments via photocatalysis is highly desirable. In this work, a novel type-II heterojunction photocatalyst, MgSn(OH)6/SnO2,was successfully prepared via a facile one-pot in situ hydrothermal method at 220 °C for 24 h. The obtained heterojunctions were characterized via powder X-ray diffraction, Fourier-transform infrared spectroscopy, transmission electron microscopy, and ultraviolet-visible diffuse reflectance spectroscopy. The photocatalytic performance was evaluated for photodegradation of tetracycline solution under ultraviolet irradiation. The initial concentration of tetracycline solution was set to be 20 mg/L. The prepared heterojunctions exhibited superior photocatalytic activity compared with the parent MgSn(OH)6and SnO2compounds. Among them, the obtained MgSn(OH)6/SnO2heterojunction with MgCl2·6H2O:SnCl4·5H2O = 4:5.2 (mmol) displayed the highest photocatalytic performance and the photodegradation efficiency conversion of 91% could be reached after 60 min under ultraviolet irradiation. The prepared heterojunction maintained its performance after four successive cycles of use. Active species trapping experiments demonstrated that holes were the dominant active species. Hydroxyl radicals and superoxide ions had minor effects on the photocatalytic oxidation of tetracycline. Photoelectrochemical measurements were used to investigate the photocatalytic mechanism. The enhancement of photocatalytic activity could be assigned to the formation of a type-II junction photocatalytic system, which was beneficial for efficient transfer and separation of photogenerated electrons and holes. This research provides an in situ growth strategy for the design of highly efficient photocatalysts for environmental restoration.
Omar S.,Omar M.,El-Subruiti G. M.,Attia N. F.,Eltaweil A.
This study presents a novel MgSn(OH) 6 /4CuS@HC photocatalyst developed via hydrothermal treatment followed by chemical precipitation. MgSn(OH) 6 /4CuS@HC was applied for wastewater treatment, targeting eight pollutants: Tetracycline, Doxycycline, Ofloxacin, 3-Nitroaniline, 2-Nitrophenol, Methyl red, Congo red, and Methylene blue. The novel photocatalyst was studied using FTIR, EDX, DRS, SEM, and PL techniques. To gain further insight into the reaction mechanism, scavenger experiments were conducted in addition to operational parameters such as pH, dosage, CuS loading on MgSn(OH) 6 @HC, pollutant initial concentration, selectivity, reusability, water source, and kinetic studies. The performance test highlighted the outstanding photocatalytic activity of templated MgSn(OH) 6 /4CuS@HC, exhibiting remarkable stability over five cycles. This performance is attributed to the direct Z-scheme mechanism and the hydrochar template, which improve charge separation, extend photocharge lifetime, and reduce the agglomeration of nanosemiconductors, thereby enhancing overall stability. This study offers a new perspective on green photocatalysts for diverse environmental applications.
Oxygen vacancies induce charge redistribution, facilitating oxygen adsorption. • S-scheme heterojunctions enable efficient charge separation while retaining high redox potential. • The dual-electron transfer pathway facilitates the rapid electron transfer to O 2 . • Lowered thermodynamic barrier of the rate-determining step by modulation of ROSs generation. Transition metal stannates are promising for efficient air purification due to their remarkable activity in volatile organic compounds (VOCs) degradation. However, the interfacial charge-transfer behavior and the fundamental mechanism of aromatic ring activation, specifically, C-H bond cleavage and ring-opening oxidation remain elusive, hindering rational catalyst design for toluene (C 7 H 8 ) mineralization. Herein, an oxygen-vacancy-enriched S-scheme heterojunction (SMSH-30) is constructed via a facile one-step hydrothermal strategy. The optimized heterostructure exhibits outstanding toluene removal (96.65%), mineralization efficiency (101.8%), and long-term stability (>600 min). Combined experimental and theoretical analyses unveil that oxygen vacancies (OVs) modulate charge transfer and reactive oxygen species (ROS) evolution: (1) OVs induce dual-channel electron migration, greatly facilitating interfacial charge transfer; (2) this enhanced transfer promotes O 2 activation into highly oxidative singlet oxygen ( 1 O 2 ); and (3) the optimized interface accelerates intermediate conversion with a favorable Gibbs free energy profile. This work provides molecular-level insights into charge dynamics and ROS modulation within S-scheme heterojunctions, offering a new paradigm for rational design of advanced photocatalysts toward deep VOC mineralization and sustainable air purification. Download: Download high-res image (156KB) Download: Download full-size image Combined experimental characterizations and density functional theory calculations revealed that oxygen vacancies serve as continuous O 2 activation centers, while the S-scheme interface promotes efficient charge separation and preserves high-redox-potential electrons for singlet oxygen generation toward complete anti-poisoning mineralization of toluene.
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