Falong Jia

Oxygen Vacancy-Mediated Photocatalysis of BiOCl: Reactivity, Selectivity, and Perspectives

Semiconductor photocatalysis is a trustworthy approach to harvest clean solar light for energy conversions, while state-of-the-art catalytic efficiencies are unsatisfactory because of the finite light response and/or recombination of robust charge carriers. Along with the development of modern material characterization techniques and electronic-structure computations, oxygen vacancies (OVs) on the surface of real photocatalysts, even in infinitesimal concentration, are found to play a more decisive role in determining the kinetics, energetics, and mechanisms of photocatalytic reactions. This Review endeavors to clarify the inherent functionality of OVs in photocatalysis at the surface molecular level using 2D BiOCl as the platform. Structure sensitivity of OVs on reactivity and selectivity of photocatalytic reactions is intensely discussed via confining OVs onto prototypical BiOCl surfaces of different structures. The critical understanding of OVs chemistry can help consolidate and advance the fundamental theories of photocatalysis, and also offer new perspectives and guidelines for the rational design of catalysts with satisfactory performance.

Iron oxide shell mediated environmental remediation properties of nano zero-valent iron

Nano zero-valent iron (nZVI) has attracted much more attention for its potential applications in the fields of environmental contaminant remediation and detoxification. Generally, nZVI consists of a zero-valent iron (Fe0) core and an iron oxide shell structure. As the underlying Fe0 core and the surface oxide shell determine the physical and chemical properties of nZVI, the nature of the oxide shell inevitably affects the organic/inorganic pollutant removal performance of nZVI, which has not been reviewed previously. In this article, we first introduce the synthesis and the oxide shell formation mechanism of core–shell structured nZVI and then discuss various characterization techniques to reveal the structure and chemical composition of the oxide shell. Subsequently, we clarify the roles of the oxide shell in the organic contaminant degradation efficiency and the molecular oxygen activation performance of nZVI and also highlight the effect of the oxide shell on heavy metal removal (including As) with nZVI. In addition, we summarize some oxide shell modification strategies to enhance the capacity and longevity of nZVI. Finally, we discuss the impacts of typical natural groundwater constituents (e.g. cations, anions, organic ligands, and dissolved oxygen) on the reactivity of nZVI and point out some unresolved issues related to the oxide shell dependent contaminant removal properties of nZVI.

Hydroxylamine Promoted Goethite Surface Fenton Degradation of Organic Pollutants

In this study, we construct a surface Fenton system with hydroxylamine (NH2OH), goethite (α-FeOOH), and H2O2 (α-FeOOH-HA/H2O2) to degrade various organic pollutants including dyes (methyl orange, methylene blue, and rhodamine B), pesticides (pentachlorophenol, alachlor, and atrazine), and antibiotics (tetracycline, chloramphenicol, and lincomycin) at pH 5.0. In this surface Fenton system, the presence of NH2OH could greatly promote the H2O2 decomposition on the α-FeOOH surface to produce ·OH without releasing any detectable iron ions during the alachlor degradation, which was different from some previously reported heterogeneous Fenton counterparts. Moreover, the ·OH generation rate constant of this surface Fenton system was 102-104 times those of previous heterogeneous Fenton processes. The interaction between α-FeOOH and NH2OH was investigated with using attenuated total reflectance Fourier transform infrared spectroscopy and density functional theory calculations. The effective degradation of organic pollutants in this surface Fenton system was ascribed to the efficient Fe(III)/Fe(II) cycle on the α-FeOOH surface promoted by NH2OH, which was confirmed by X-ray photoelectron spectroscopy analysis. The degradation intermediates and mineralization of alachlor in this surface Fenton system were then systematically investigated using total organic carbon and ion chromatography, liquid chromatography-mass spectrometry, and gas chromatography-mass spectrometry. This study offers a new strategy to degrade organic pollutants and also sheds light on the environmental effects of goethite.

Microwave‐Induced Formation of Platinum Nanostructured Networks with Superior Electrochemical Activity and Stability

Platinum nanostructured networks (PNNs) can be synthesized through the chemical reduction of H(2)PtCl(6) by benzyl alcohol under microwave irradiation without the introduction of any surfactants, templates, or seeds. The synthesis route utilizes benzyl alcohol as both the reductant and the structure-directing agent, and thus, the process is particularly simple and highly repeatable. The formation of the PNN structure was ascribed to the collision-induced fusion of Pt nanocrystals owing to the cooperative functions of microwave irradiation and benzyl alcohol. Compared with a commercial Pt/C catalyst, the as-prepared PNNs possessed superior electrochemical activity and stability on the oxidation of methanol because of the unique 3D nanostructured networks and abundant defects formed during the assembly process. This study may provide a facile microwave-induced approach for the synthesis of other 3D nanostructured noble metals or their alloys.

Ascorbate-Promoted Surface Iron Cycle for Efficient Heterogeneous Fenton Alachlor Degradation with Hematite Nanocrystals

This study reports the H2O2 activation with different hematite nanocrystals and ascorbate ions for the herbicide alachlor degradation at pH 5. We found that hematite nanoplates (HNPs) exposed with {001} facets exhibited better catalytic performance than hematite nanocubes (HNCs) exposed with {012} facets, which was attributed to the formation of inner-sphere iron-ascorbate complexes on the hematite facets. The 3-fold undercoordination Fe cations of {001} facet favors the formation of inner-sphere iron-ascorbate complexes, while the 5-fold undercoordination Fe cations of {012} facet has stereo-hindrance effect, disfavoring the complex formation. The surface area normalized alachlor degradation rate constant (23.3 × 10-4 min-1 L m-2) of HNPs-ascorbate Fenton system was about 2.6 times that (9.1 × 10-4 min-1 L m-2) of HNCs-ascorbate counterpart. Meanwhile, the 89.0% of dechlorination and 30.0% of denitrification in the HNPs-ascorbate Fenton system were also significantly higher than those (60.9% and 13.1%) of the HNCs-ascorbate one. More importantly, the reductive dissolution of hematite by ascorbate was strongly coupled with the subsequent H2O2 decomposition by surface bound ferrous ions through surface iron cycle on the hematite facets in the hematite-ascorbate Fenton systems. This coupling could significantly inhibit the conversion of surface bound ferrous ions to dissolved ones, and thus account for the stability of hematite nanocrystals. This work sheds light on the internal relationship between iron geochemical cycling and contaminants degradation, and also inspires us to utilize surface iron cycle of widely existent hematite for environmental remediation.

One-pot synthesis of spring-like superstructures consisting of layered tin(IV) hydrogen phosphate nanodisks

Spring-like superstructures consisting of layered tin(IV) hydrogen phosphate nanodisks can be obtained via a one-pot solvothermal reaction of tin tetrachloride and phosphoric acid in ethanol. These superstructures are active anode materials for the lithium-ion battery.

Mn2+ promoted Cr(VI) reduction with oxalic acid: The indispensable role of In-situ generated Mn3+

In this study, we demonstrate that Mn2+ can greatly promote the Cr(VI) reduction by oxalic acid at pH<5 via an induction period and a subsequent auto-acceleration process. The Cr(VI) reduction rate constant during the late auto-acceleration process was about 10 times that of the initial induction period. Characterization results revealed that this interesting two-step Cr(VI) reduction phenomenon was attributed to the in-situ generated Mn3+ by the oxidation of Mn2+ with Cr(VI) in the presence of oxalic acid during the induction period. The in-situ generated Mn3+ might complex with oxalate and Cr(VI) to produce a ternary complex, thus facilitating the electron transfer from oxalate to Cr(VI) to automatically accelerate the Cr(VI) reduction process. These findings shed insight into the possible roles of widely existed Mn ions (Mn2+ and Mn3+) and oxalic acid in the transformation of Cr(VI) in natural aquatic environment, and also provided an efficient way to remediate Cr(VI)-containing acid wastewater.