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A novel CdS/ZnO heterojunction constructed of zero-dimensional (0D) CdS quantum dots (QDs) and two-dimensional (2D) ZnO nanosheets (NSs) was rationally designed for the first time. The 2D ZnO NSs were assembled into ZnO microflowers (MFs) via an ultrasonic-assisted hydrothermal procedure (100 °C, 12 h) in the presence of a NaOH solution (0.06 M), and CdS QDs were deposited on both sides of every ZnO NS in situ by using the successive ionic-layer absorption and reaction method. It was found that the ultrasonic treatment played an important role in the generation of ZnO NSs, while NaOH was responsible to the assembly of a flower-like structure. The obtained CdS/ZnO 0D/2D heterostructures exhibited remarkably enhanced photocatalytic activity for hydrogen evolution from water splitting in comparison with other CdS/ZnO heterostructures with different dimensional combinations such as 2D/2D, 0D/three-dimensional (3D), and 3D/0D. Among them, CdS/ZnO-12 (12 deposition cycles of CdS QDs) exhibited the highest hydrogen evolution rate of 22.12 mmol/g/h, which was 13 and 138 times higher than those of single CdS (1.68 mmol/g/h) and ZnO (0.16 mmol/g/h), respectively. The enhanced photocatalytic activity can be attributed to several positive factors, such as the formation of a Z-scheme photocatalytic system, the tiny size effect of 0D CdS QDs and 2D ZnO NSs, and the intimate contact between CdS QDs and ZnO NSs. The formation of a Z-scheme photocatalytic system remarkably promoted the separation and migration of photogenerated electron-hole pairs. The tiny size effect effectively decreased the recombination probability of electrons and holes. The intimate contact between the two semiconductors efficiently reduced the migration resistance of photogenerated carriers. Furthermore, CdS/ZnO-12 also presented excellent stability for photocatalytic hydrogen evolution without any decay within five cycles in 25 h.

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In this work, a novel porous nanoneedlelike MnO-FeO catalyst (MnO-FeO nanoneedles) was developed for the first time by rationally heat-treating metal-organic frameworks including MnFe precursor synthesized by hydrothermal method. A counterpart catalyst (MnO-FeO nanoparticles) without porous nanoneedle structure was also prepared by a similar procedure for comparison. The two catalysts were systematically characterized by scanning and transmission electron microscopy, X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy, hydrogen temperature-programmed reduction, ammonia temperature-programmed desorption, and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFT), and their catalytic activities were evaluated by selective catalytic reduction (SCR) of NO by NH. The results showed that the rationally designed MnO-FeO nanoneedles presented outstanding low-temperature NH-SCR activity (100% NO conversion in a wide temperature window from 120 to 240 °C), high selectivity for N (nearly 100% N selectivity from 60 to 240 °C), and excellent water resistance and stability in comparison with the counterpart MnO-FeO nanoparticles. The reasons can be attributed not only to the unique porous nanoneedle structure but also to the uniform distribution of MnO and FeO. More importantly, the desired Mn/Mn and O/(O + O) ratios, as well as rich redox sites and abundant strong acid sites on the surface of the porous MnO-FeO nanoneedles, also contribute to these excellent performances. In situ DRIFT suggested that the NH-SCR of NO over MnO-FeO nanoneedles follows both Eley-Rideal and Langmuir-Hinshelwood mechanisms.

Rational design of CdS@ZnO core-shell structure via atomic layer deposition for drastically enhanced photocatalytic H evolution with excellent photostability, Nano Energy, http://dx.doi.org/10. 1016/j.nanoen.2017.06.047 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. number of deposition cycles, and the obtained CdS@ZnO with 100 ALD deposition cycles displays the optimal photocatalytic H 2 evolution rate of 11.36 mmol/g/h. WhenPt and PdS are used as the co-catalysts, the H 2 evolution rates are further enhanced to 71.39 and 98.82 mmol/g/h, respectively, which are 4.1 and 5.7 times higher than the highest reported value (17.40 mmol/g/h) among CdS-ZnO catalyst systems. Detailed characterization reveals that the drastically enhanced photocatalytic activity can be attributed to not only efficient space separation of the photo-induced electrons and holes resulted from the formation of a direct Z-scheme photocatalytic system between crystalline ZnO and CdS, but also the intimate contact at molecular scale between the two semiconductors. Due to the coverage of ALD-prepared crystalline ZnO shell on CdS core, the CdS@ZnO core-shell structures exhibit excellent photostability. Graphical abstract3 / 31