Unexpected rapid photo-catalytic decolourisation/degradation of organic pollutants over highly active hetero junction based vanadium phosphate catalyst

Investigation of the main factor affecting the NOx distribution in the street canyon with the photo-catalytic wall

To find out the most contaminated street region and protect the pedestrian with the photo-catalytic equipment to decrease the hazard of oxynitride (NOx), Computational Fluid Dynamics (CFD) simulation could be used to research the main factor affecting the statistical characteristics of the oxynitride distribution in the urban street canyon with the photo-catalytic building walls. Additionally, the connection was investigated and focused on the swirling flow and oxynitride concentration to find out the root of the main factor affecting oxynitride distribution. The simulation results showed that there was one three-dimensional swirling flow in the whole canyon and the statistical concentration was straightforwardly related to the swirling or whirling flow structure (such as eddy). The characteristics had been confirmed that the whirling flow structure affected the complex oxynitride distribution in the street canyon with the photo-catalytic building walls. Furthermore, one formula was found which described the oxynitride concentration constrained by the street canyon. This study illustrated that different sections in the canyon had various patterns of the whirling flow structure (swirling flow) and oxynitride. In the symmetrical portion of the street canyon (in the middle of the street length), there is one concise equation to describe the NOx concentration affected by the turbulence intensity. Moreover, the equation was presented as CR = 1.094 + 0.11e-I, where I was the turbulence intensity and CR was the oxynitride relative concentration in the street canyon.

Environmentally benign synthesis of Co3O4-SnO2 heteronanorods with efficient photocatalytic performance activated by visible light

One-dimensional (1D) heterostructured photocatalysts with controllable texture properties and compositions have attracted increasing interest owing to their unique optical, structural, and electronic advantages. Herein, 1D Co₃O₄-SnO₂ heteronanorods were rationally designed and synthesized through a facile solution-based approach. Benefiting from both of their heterostructural and compositional characteristics, the resulting Co₃O₄-SnO₂ heteronanorods exhibit high photocatalytic performance for the degradation of Rhodamine B (RhB) under visible-light irridation. In particular, the photocatalyst with a Co₃O₄/SnO₂ mass ratio of 1:1 provides the best photocatalytic performance, which can degrade 90% RhB within 120 min. Besides, several reaction parameters affecting RhB degradation, such as churning time, calcination temperature and pH value, are investigated in detail. The enhanced photocatalytic activity can be attributed to the broadening of absorption spectrum to visible-light regions and the efficient charge separation of photogenerated electron-hole pairs due to the formed p-n heterojunctions. The strategy reported here can be able to expand to fabricate other heterostructured photocatalysts for practical applications in the fields of photocatalysis, water splitting, and solar cells.

Bridging the gap between laboratory and application in photocatalytic water purification

Despite a large number of publications in the field, photocatalytic water treatment is still somewhat disconnected from real world application and we highlight recent developments to address this.

A separation-free 3D network ZnO/rGO–rGH hydrogel: adsorption enriched photocatalysis for environmental applications

This study describes the encapsulation of ZnO by reduced graphene oxide to form a composite (ZnO/rGO) that can be incorporated into graphene to form hydrogels (ZnO/rGO–rGH) with three-dimensional (3D) network structures. The unique surface adsorption characteristics of graphene make ZnO/rGO–rGH materials have the ability of fast adsorption and desorption. Meanwhile, the combination of graphene and ZnO nanoparticles can promote the separation efficiency of electrons and holes and improve the photocatalytic activity. The sample showed the highest adsorption-photocatalysis synergistic activity and removed 100% of the BPA (10 mg L⁻¹) within 20 min under UV irradiation. The purification efficiency of ZnO/rGO–rGH can reach more than 90% after 5 rounds of repeated use. We also measured the performance of ZnO/rGO–rGH in removing BPA under flow conditions, and the results showed that this approach with ZnO/rGO–rGH removed 100% of the BPA in 16 h.

Proposed mechanism for photocatalytic BPA degradation by ZnO/rGO–rGH under ultraviolet light illumination.