Construction of heterojunctions has aroused great interest recently in the photocatalysis field because of the special electronic band structure and unique physicochemical properties. In this work, a novel 0D/3D CuO/ZnO heterojunction was obtained via in situ deposition of CuO nanoparticles on the flowerlike ZnO surface using the wet chemistry method. After depositing CuO nanoparticles onto the ZnO, the CuO/ZnO heterojunction exhibits enhanced visible-light harvesting and effective separation of the photogenerated electron–hole pairs compared with those in the pure ZnO. The photocatalytic removal efficiency of phenol over the CuO/ZnO heterojunction is up to 78% under the irradiation of the light, which is ∼2 and ∼4 times higher than those of the pristine ZnO and CuO, respectively. This composite also presents good durability and stability for phenol degradation in the photocatalytic reactions. Additionally, in the photodegradation system of the CuO/ZnO heterojunction, the superoxide radicals (•O2 –) and hydroxyl radicals (•OH) are confirmed as the active species by the trapping experiments. This research provides a promising way to achieve 0D/3D heterojunctions for the application in environmental purification and remedy.

Development of a high-efficiency heterojunction with an improved photocatalytic property is regarded as a promising way to decontaminate wastewater. Herein, the direct novel Z-scheme heterojunction formed between CeO 2 nanoparticles and hierarchical ZnO was synthesized through the wet chemistry method and then the heat-treatment technique. The as-synthesized ZnO/CeO 2 composites display highly enhanced photocatalytic rhodamine B (RhB) degradation compared with pristine ZnO and CeO 2 . Specifically, ZnO/CeO 2 -3 (mass fraction of CeO 2 , 30%) shows good photostability and the best removal efficiency for photodegradated RhB, which are almost 2.5 and 1.7 times than pristine ZnO and CeO 2 , respectively. On the basis of the detailed characterizations and the degradation behavior of as-prepared samples over RhB, the formed heterojunction between the hierarchical ZnO and CeO 2 nanoparticles is confirmed as the direct Z-scheme heterojunction. The heterojunction system shows fast transfer, high-efficiency separation, and long lifetime of photoinduced charge carriers, as well as enhanced redox capacity. This study affords a novel approach to construct ZnO-based Z-scheme heterojunctions for the photocatalytic applications.

Knowledge on the initial and intermediate pyrolysis products of biomass is essential for the mechanistic investigation of biomass pyrolysis and further optimization of upgrading processes. The conventional method can only detect the final products, which do not resemble the initial or intermediate pyrolysis products. Here, we introduce a direct orifice sampling combined with atmospheric pressure photoionization mass spectrometry (APPI-MS) for in situ online analysis of the evolved volatile initial products from the pyrolysis of biomass. Pyrolysis experiments of both dimeric model compound (guaiacylglycerol-β-guaiacyl ether, GGGE) and poplar wood were carried out to validate the generality of the method. Generally, secondary reactions can be reduced by shortening the distance between the sample and sampling orifice. Large molecular-weight initial products up to trimers were detected during the pyrolysis of poplar wood, and no initial products larger than trimers were detected. It is inferred that in situ APPI immediately after sample extraction ensures efficient and effective product detection. Furthermore, the present work offers a promising feasible method for online tracing of reaction intermediates not only in pyrolysis but also in various reactive processes (e.g., catalytic reaction, oxidation) under operando conditions.

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