One-pot synthesis of CeO2/Mg-Al layered double oxide nanosheets for efficient visible-light induced photo-reduction of Cr(VI)

Constructing CoAl-LDO/MoO3-x S-scheme heterojunctions for enhanced photocatalytic CO2 reduction

Converting CO2 into chemicals and fuels by solar energy can alleviate global warming and solve the energy crisis. In this work, CoAl-LDO/MoO3-x (LDO/MO) composites were successfully prepared and achieved efficient CO2 reduction under visible light. The CoAl-layered double oxides (CoAl-LDO) evolved from CoAl-layered double hydroxide (CoAl-LDH) exhibited a more robust structure, broader light absorption, and improved CO2 adsorption ability. The local surface plasmon resonance (LSPR) effect excited by nonstoichiometric MoO3-x broadened the photo-response range of CoAl-LDO/MoO3-x. In addition, constructing step-scheme (S-scheme) heterojunctions could simultaneously optimize the migration mechanism of photogenerated electrons and holes, and retain carriers with strong redox ability. Therefore, the production rates of CO and CH4 on the optimal LDO/MO composite were 7 and 9 times higher than the pristine CoAl-LDH, respectively. This work hybridizes oxidation photocatalysts and LDO-based materials to optimize the charge separation and migration mechanisms, which guides the modification of LDO-based materials.

Heterogeneous ZnS-zinc carbonate hydroxide micro-belt for Cr(VI) reduction under simulated sunlight

Heterogeneous ZnS-zinc carbonate hydroxide (ZnS-ZCH) micro-belt was facilely synthesized and the composite belt displayed a dramatic enhancement for the response to the simulated sunlight, as indicated by a more than...

Flower-like Bi2S3-In2S3 heterojunction for efficient solar light induced photoreduction of Cr(VI)

To develop Bi₂S₃-based heterojunction for efficient solar light induced photoreduction of Cr(VI), flower-like Bi₂S₃-In₂S₃ composites consisted of nanorods were prepared via a microwave-assisted hydrothermal route. In contrast with pure Bi₂S₃, Bi₂S₃-In₂S₃ composites exhibited the enhanced photoreduction activity while the decreased adsorption capacity for Cr(VI) removal. The best removal efficiency of 70 mg L^-1 Cr(VI) solution (99.86%) was achieved by the optimal 3-Bi₂S₃-In₂S₃ with a Bi/In molar ratio of 4:1 within 140 min. It's ascribed to the narrow band gap for strengthened visible-light response, the tight interface between Bi₂S₃ and In₂S₃ for rapid transfer and separation of charge carriers, and the enough S vacancies for highly-efficient active sites of adsorption-photoreduction. However, the long-term photo-corrosion resulted in the slightly inferior reusability of 3-Bi₂S₃-In₂S₃ under solar light irradiation after five cycles.

Effective in-situ reduction of Cr(VI) from leather wastewater by advanced reduction process based on CO2·- with visible-light photocatalyst

Advanced reduction process (ARP) has drawn an increasing interest as a new manner for removing oxidative pollutants in water. In this paper, we demonstrate the possibility of in-situ reduction of Cr(VI) by CO₂^·- produced from formate originally existing in leather wastewater by visible-light-driven ARP containing black TiO₂ photocatalyst. The prepared black TiO₂ with nanotube structure achieves remarkable enhanced the reduction rate of Cr(VI) as high as 96.2% (k = 0.0114 min^-1) in the presence of formate, which is approximately 4.75 times than that of 56.3% (k = 0.0024 min^-1) in the absence under 120 min visible-light irradiate at unadjusted pH. The results exhibit a distinct contrast with commercial TiO₂ (P25). A series of control experiments are also performed, indicating that formate is able to convert the oxidative environment into a highly reductive one, and the formate concentration, black TiO₂ dosage and pH may greatly impact on the Cr(VI) reduction rate. According to the electron spin resonance (ESR) measurement, CO₂^·- radicals can be directly verified as dominate radical in this system. Moreover, this system appears to be attractive for creating photochemical systems where in-situ production of CO₂^·- radicals may be realized by using formate. Then this in-situ ARP system will provide a new perspective for the Cr(VI) removing, which makes leather wastewater treatment much easier and more sustainable in the future.

Unravelling the visible light-assisted catalytic prowess of an n–n type In2S3/CeO2 Z-scheme heterojunction towards organic and inorganic water pollution mitigation

The exploitation of visible light active photocatalysts for the removal of various pollutants has been given tremendous consideration in water and wastewater treatment.