Changhai Liu

Fabrication of the ternary heterojunction Cd0.5Zn0.5S@UIO-66@g-C3N4 for enhanced visible-light photocatalytic hydrogen evolution and degradation of organic pollutants

A novel ternary heterojunction Cd0.5Zn0.5S@UIO-66@g-C3N4 (Cd0.5Zn0.5S@UCN) has been prepared by the in situ hydrothermal and precipitation approach, which exhibits superior photocatalytic activity for H2 generation and MO degradation under visible-light irradiation. The Cd0.5Zn0.5S@UCN30 composite shows the maximum photocatalytic H2 production rate (1281.1 μmol h−1 g−1) that is about 32.9 and 2.7 times higher than UIO-66@g-C3N4 and pristine Cd0.5Zn0.5S, respectively. Besides, the Cd0.5Zn0.5S@UCN30 heterojunction indicates the superior degradation efficiency of MO (82%) in 120 min. The improved photocatalytic activity of the Cd0.5Zn0.5S@UCN heterostructure can be assigned to its large surface area, enhanced visible-light absorption ability and high-efficiency separation of photogenerated electron–hole pairs, which are proved by the results of photocurrent and EIS analyses. Moreover, the photocatalytic mechanism based on the ternary heterojunction Cd0.5Zn0.5S@UCN is discussed and the transfer and separation process of photogenerated electron–hole pairs is also proposed. This work demonstrates that a novel ternary noble-metal-free photocatalytic system could provide a scientific basis for the application in the field of energy production and pollution removal.

Hydrothermal fabrication of α-SnWO4/g-C3N4 heterostructure with enhanced visible-light photocatalytic activity

The novel α-SnWO4/g-C3N4 composites have been successfully synthesized by a facile hydrothermal method. The crystalline structure, physicochemical property and morphology of the as-prepared samples were characterized by XRD, SEM, TEM, UV–vis and PL. Compared to the pristine α-SnWO4 and g-C3N4, the α-SnWO4/g-C3N4 heterostructure exhibited enhanced photocatalytic activity toward the degradation of Rhodamine B (RhB) under visible light irradiation, which can be attributed to the effective electrons/holes transfer and separation, due to the heterojunction formed between α-SnWO4 and g-C3N4. Moreover, the α-SnWO4/g-C3N4 demonstrated good recyclability properties which were beneficial for its practical application. The photocatalytic mechanism of the α-SnWO4/g-C3N4 was also discussed.

Construction of CdS@UIO-66-NH 2 core-shell nanorods for enhanced photocatalytic activity with excellent photostability

A novel class of CdS@UIO-66-NH2 core shell heterojunction was fabricated by the facile in-situ solvothermal method. Characterizations show that porous UIO-66-NH2 shell not only allows the visible light to be absorbed on CdS nanorod core, but also provides abundant catalytic active sites as well as an intimate heterojunction interface between UIO-66-NH2 shell and CdS nanorod core. By taking advantage of this property, the core-shell composite presents highly solar-driven photocatalytic performance compared with pristine UIO-66-NH2 and CdS nanorod for the degradation of organic dyes including malachite green (MG) and methyl orange (MO), and displays superior photostability after four recycles. Furthermore, the photoelectrochemical performance of CdS@UIO-66-NH2 can be measured by the UV-vis spectra, Mott-Schottky plots and photocurrent. The remarkably enhanced photocatalytic activity of CdS@UIO-66-NH2 can be ascribed to high surface areas, intimate interaction on molecular scale and the formation of one-dimensional heterojunction with n-n type. Whats more, the core-shell heterostructural CdS@UIO-66-NH2 can facilitate the effective separation and transfer of the photoinduced interfacial electron-hole pairs and protect CdS nanorod core from photocorrosion.

The effect of fast and slow surface states on photoelectrochemical performance of hematite photoanodes fabricated by electrodeposition and hydrothermal methods

The hematite films prepared by electrodeposition (ED) and hydrothermal (HT) methods have similar nanorods morphology and the same length. However, the hematite prepared by HT method has higher photocurrent density and negative shift of onset potential. The samples are systematically characterized by scanning electron microscopy, UV–Vis spectra, X-ray diffractometry and photoelectrochemical measurements. The results reveal that the enhanced photoelectrochemical (PEC) performance of HT hematite is attributed to the superior surface charge injection efficiency, which is caused by a slower surface recombination rate rather than a more catalytically active hematite surface. And the slower surface recombination rate can be attributed to the absence of the slow surface states CSS2. This work provides an in-depth understanding of the reasons for the different PEC performance of hematite photoanodes fabricated by ED and HT methods, which is of certain significance in guiding the modification of hematite photoanodes prepared by the two typical routes in PEC water splitting system.