1. Pollutants Control Chemistry
The rapid economic development brings more and more serious environmental problems, which is mainly caused by the chemical pollutants. The major purpose of pollutants control chemisty is study the chemical issues in the mechanisms and technologies related to pollutants control and remediation,aiming to develop economic and efficient pollutants control and remediation techniques, and provide theoretical basis for clean production process. Our group mainly focuses on the develop of pollutant control technology with environment benign iron and molecular oxygen, solving the key scientific problems faced for the nanoscale zero-valent iron reactivity tuning and the molecular oxygen activation. Recently, we revealed the core-shell structure dependent property of nanoscale zero-valent iron on the pollutant removal with molecular oxygen activation, and proposed a novel molecular oxygen activation mechanism to explain this phenomenon (please see the following figure). We are now seeking for some ligands to improve the nanoscale zero-valent iron reactivity,and clarifying the interface reaction of nanoscale zero-valent iron and the generation of reactive oxygen species.
Iron is the fourth most abundant transition metal in the earth's crust, widely existsin aerosol, soil components, natural water systems, airborne minerals dust, animals and plants. Because of its ubiquity and redox property iron plays important roles in the bio-geochemical cycles and chemical evolution processes of living organisms. Asiron cycle is one of the most important and multifunctional bio-geochemicalcycles, the study of iron cycle and environmental effects becomes the international research frontier and hot topic, and also the key point to clarify the abiotic geochemical cycles of red clay soil. The solution to solve iron cycle issue lies in the understanding of adsorption/desorption, redox process and electron transfer on the suface/interface of iron oxide and iron (oxy)hydroxide natural minerals, as well as their environmental effects at an atomic level. Recently, we synthesized hematite nanocrystals with different facet exposure, and utilized synchrotron−based Cr K–edge extended X−ray absorption fine structure (EXAFS) spectroscopy, in situ attenuated total reflectance Fourier transform infrared (ATR−FTIR) spectroscopy, in combination with density−functional theory (DFT) calculation, to systematically investigated the adsorption/desorption,redox process and electron transfer on the different facets of hematite nanocrystals (please see the following figure), aiming to clarify environmental effects of hematite at an atomic level, understand the complex geochemical cycles of red clay soil and the intrinsic relationship between iron cycle and pollutant transport and transfer, and then realize environmental remediationand recovery with iron cycle manipulation.
2. Photocatalysis
Photocatalysis can utilize solar energy to produce ·OH to oxidize organic pollutants, and also split water to generate H2, thus exhibit attractive application potentials to solve energy crisis and environmental pollution. However, its low quantum efficiency restricts its wide applications in the energy and environmental fields. How to improve the photocatalytic reaction efficiency is always the hot topic of photocatalysis. Our group aims to develop new low-cost strategies to prepare high surface area visible light photocatalysts, clarify their molecular oxygen activation, photocarriers separation and structure-performance relationship, and thus improve their pollutant degradation efficiency via molecular oxygen activation under ambient temperature and pressure with utilization of solar energy. For instance, we recently selectively synthesized BiOCl single-crystalline nanosheets with exposed {001} and {010} facets, and found that the resulting BiOCl single-crystalline nanosheets with exposed {001} facets exhibited higher activity on direct semiconductor photoexcitation pollutant degradation under UV light, but the counterpart with exposed {010} facets possessed superior activity on indirect dye photosensitization degradation under visible light (pleasesee the following figure).These findings will deepen our understanding of molecular oxygen activation on surface structures in photocatalytic reactions and allowus to sensitively manipulate the reaction processes.
Nitrogen is needed by all living organisms to build proteins, nuclei acids and many other biomolecules.Though constituting about 78% of the Earth’s atmosphere, nitrogen, in its molecular form, is unusable to most organisms because of its strong non-polar N-N covalent triple bond towards dissociation, negative electron affinity, high ionization energy and so on. Thus, the industrial fixation of N2 to NH3 through the classical Haber-Bosch process has to be conducted under drastic conditions (15~25 MPa, 300~550 oC) in the presence of iron-based catalyst to overcome the kinetic limitation, while consumes 1~2% of the world’s annual energy supply and produces 2.3 ton of fossil-derived CO2 per year. In view of the fossil fuels shortage and global climate change,nitrogen fixation through less energy-demanding process is therefore achallenging and long-term goal. In contrast, nature uses nitrogenase in vivo to catalytically reduce N2 to NH3 under mild conditions, because its MoFe-cofactor can activate N2. Our group employed BiOBr nanosheets of oxygen vacancies as the catalyst, and demonstrated that the designed catalytic oxygen vacancies of BiOBr nanosheets on the exposed {001} facets, with the availability of localized electrons for π-back donation, have the ability to activate the adsorbed N2, which can thus be efficiently reduced to NH3 by the interfacial electrons transferred from the excited BiOBr nanosheets (please see the following figure). This study might open up a new vista to fix atmospheric N2 to NH3 through the less energy-demanding photochemical process.Although photocatalytic reduction is unlikely to replace the Haber-Bosch process at present, this study might open up a new vista to fix atmospheric N2 to NH3 through less energy-demanding photochemical process.
3. Environmental Nanomaterials
Nanomaterials of high surface area as well as strong absorb and catalytic abilities have gradually been used in the environmental remediation field by replacing the traditional materials, and thus might be a important choice of future pollutant control materials. It is of great academic and application importance to develop high efficient environmental pollutant control materials for the applications in the fields of air, water and soil remediation and recovery. Our group has designed some high surface area environmental nanomaterials and employed them for the high efficient removal of heavy metal ions ( e.g. Cr6+,Cu2+, Cd2+ and Pb2+ etc) from water.
