A Functionally Asymmetric Janus Hygro-Photothermal Hybrid for Atmospheric Water Harvesting in Arid Regions.

Metal-organic frameworks (MOFs) are high-performance adsorbents for atmospheric water harvesting but have poor water-desorption ability, requiring excess energy input to release the trapped water. Addressing this issue, a Janus-structured adsorbent with functional asymmetry is presented. The material exhibits contrasting functionalities on either face - a hygroscopic face interfaced with a photothermal face. Hygroscopic aluminum fumarate MOF and photothermal CuxS layers are in-situ grown on opposite sides of a Cu/Al bimetallic substrate, resulting in a CuxS-Cu/Al-MOF Janus hygro-photothermal hybrid. The two faces serve as independent "factories" for photothermal conversion and water adsorption-desorption respectively, while the interfacing bimetallic layer serves as a "heat conveyor belt" between them. Due to the high porosity and hydrophilicity of the MOF, the hybrid exhibits a water-adsorption capacity of 0.161 g g-1 and a fast adsorption rate (saturation within 52 min) at 30% relative humidity. Thanks to the photothermal CuxS, the hybrid can reach 71.5 °C under 1 Sun in 20 min and desorb 97% adsorbed water in 40 min, exhibiting a high photothermal conversion efficiency of over 90%. CuxS-Cu/Al-MOF exhibits minimal fluctuations after 200 cycles, and its water-generation capacity is 3.21 times that of powdery MOF in 3 h in a self-designed prototype in one cycle.

Accelerated oxidation of VOCs via vacuum ultraviolet photolysis coupled with wet scrubbing process.

Vacuum ultraviolet (VUV) photolysis is a facile method for volatile organic compounds (VOCs) elimination, but is greatly limited by the relatively low removal efficiency and the possible secondary pollution. To overcome above drawbacks, we developed an efficient method for VOCs elimination via VUV photolysis coupled with wet scrubbing process. In this coupled process, volatile toluene, a representative of VOCs, was oxidized by the gas-phase VUV photolysis, and then scrubbed into water for further oxidation by the liquid-phase VUV photolysis. More than 96% of toluene was efficiently removed by this coupled process, which was 2 times higher than that in the gas-phase VUV photolysis. This improvement was attributed to the synergistic effect between gas-phase and liquid-phase VUV photolysis. O3 and HO• are the predomination reactive species for the toluene degradation in this coupled process, and the generation of O3 in gas-phase VUV photolysis can efficiently enhance the HO• production in liquid-phase VUV photolysis. The result from in-situ proton transfer reaction ionization with mass analyzer (PTR-MS) further suggested that most intermediates were trapped by the wet scrubbing process and efficiently oxidized by the liquid-phase VUV photolysis, showing a high performance for controlling the secondary pollution. Furthermore, the result of stability test and the reuse of solution demonstrated that this coupled process has a highly stable and sustainable performance for toluene degradation. This study presents an environmentally benign and highly efficient VUV photolysis for gaseous VOCs removal in the wet scrubbing process.

Photocatalytic Oxidation for Volatile Organic Compounds Elimination: From Fundamental Research to Practical Applications.

Photocatalysis is regarded as one of the most promising technologies for indoor volatile organic compounds (VOCs) elimination due to its low cost, safe operation, energy efficiency, and high mineralization efficiency under ambient conditions. However, the practical applications of this technology are limited, despite considerable research efforts in recent decades. Until now, most of the works were carried out in the laboratory and focused on exploring new catalytic materials. Only a few works involved the immobilization of catalysts and the design of reactors for practical applications. Therefore, this review systematically summarizes the research and development on photocatalytic oxidation (PCO) of VOCs, with emphasis on recent catalyst's immobilization and reactor designs in detail. First, different types of photocatalytic materials and the mechanisms for PCO of VOCs are briefly discussed. Then, both the catalyst's immobilization techniques and reactor designs are reviewed in detail. Finally, the existing challenges and future perspectives for PCO of VOCs are proposed. This work aims to provide updated information and research inspirations for the commercialization of this technology in the future.

A review of volatile organic compounds (VOCs) degradation by vacuum ultraviolet (VUV) catalytic oxidation.

Volatile organic compounds (VOCs), one of the most important gaseous air pollutants, are getting more and more attention, and a lot of technologies have been studied and applied to eliminate VOCs emissions. Advanced oxidation processes (AOPs) are considered as one of the most promising techniques used for the degradation of VOCs. Vacuum ultraviolet (VUV) catalytic oxidation system is a typical composite AOPs system involving several processes such as VUV photodegradation, photocatalytic oxidation (PCO), ozone catalytic oxidation (OZCO) and their combinations. VUV based catalytic oxidation processes have been intensively studied for degrading VOCs. This review summarizes the recent studies on the use of VUV catalytic oxidation for degrading VOCs. All the processes involved in VUV catalytic oxidation and their combinations have been reviewed. Studies of VOCs degradation by VUV catalytic oxidation can be generally divided into two aspects: developments of catalysts and mechanistic studies. Principles of different processes, strategies of catalyst development and reaction mechanism are summarized in this review. Two directions of prospective future work were also proposed.

The efficacy of vacuum-ultraviolet light disinfection of some common environmental pathogens.

BACKGROUND: This study is to elucidate the disinfection effect of ozone producing low-pressure Hg vapor lamps against human pathogens. Ozone producing low-pressure Hg vapor lamps emit mainly 254 nm ultraviolet light C (UVC) with about 10% power of Vacuum-ultraviolet (VUV) light at 185 nm. The combination of UVC and VUV can inactivate airborne pathogens by disrupting the genetic materials or generation of reactive oxygen species, respectively. In this study, inactivation of common bacteria including Escherichia coli ATCC25922 (E. coli), Extended Spectrum Beta-Lactamase-producing E. coli (ESBL), Methicillin-resistant Staphylococcus aureus (MRSA) and Mycobacterium tuberculosis (MTB), and that of influenza A viruses H1N1 and H3N2 under the radiation from ozone producing low-pressure Hg vapor lamps was examined. Log reduction values at different treatment durations were determined. METHODS: In vitro tests were carried out. Various bacterium and virus suspensions were added onto nitrocellulose filter papers and subjected to the illumination from ozone producing low-pressure Hg vapor lamps. The extents of pathogen inactivation at different illumination times were investigated by conducting a series of experiments with increasing duration of illumination. log10 reduction in CFU/ml and reduction at log10(TCID50) were respectively measured for bacteria and viruses. The disinfection effectiveness of this type of lamps against the pathogens under the environment with a moderate barrier to light was therefore evaluated. RESULTS: Ozone producing low-pressure Hg vapor lamp successfully inactivated these human pathogens. Nevertheless, among these pathogens, disinfection of MTB required more intense treatment. In the best tested situation, 3-log10 inactivation of pathogens can be achieved with ≤10 min of VUV treatment except MTB which needed about 20 min. This demonstrated the high resistance against UV disinfection of MTB. CONCLUSIONS: Following the criteria that valid germicidal results can be reflected with 3-log10 inactivation for bacteria, 4-log10 inactivation for viruses and 5-log10 inactivation for MTB, most of the bacteria required ≤10 min of VUV treatment, 20 min for the influenza viruses while MTB needed about 30 min VUV treatment. This indicated that VUV light is an effective approach against different environmental microorganisms.

Enhanced Performance and Conversion Pathway for Catalytic Ozonation of Methyl Mercaptan on Single-Atom Ag Deposited Three-Dimensional Ordered Mesoporous MnO2.

In this study, Ag deposited three-dimensional MnO2 porous hollow microspheres (Ag/MnO2 PHMSs) with high dispersion of the atom level Ag species are first prepared by a novel method of redox precipitation. Due to the highly efficient utilization of downsized Ag nanoparticles, the optimal 0.3% Ag/MnO2 PHMSs can completely degrade 70 ppm CH3SH within 600 s, much higher than that of MnO2 PHMSs (79%). Additionally, the catalyst retains long-term stability and can be regenerated to its initial activity through regeneration with ethanol and HCl. The results of characterization of Ag/MnO2 PHMSs and catalytic performance tests clearly demonstrate that the proper amount of Ag incorporation not only facilitates the chemi-adsorption but also induces more formation of vacancy oxygen (Ov) and lattice oxygen (OL) in MnO2 as well as Ag species as activation sites to collectively favor the catalytic ozonation of CH3SH. Ag/MnO2 PHMSs can efficiently transform CH3SH into CH3SAg/CH3S-SCH3 and then oxidize them into SO42- and CO2 as evidenced by in situ diffuse reflectance infrared Fourier transform spectroscopy. Meanwhile, electron paramagnetic resonance and scavenger tests indicate that •OH and 1O2 are the primary reactive species rather than surface atomic oxygen species contributing to CH3SH removal over Ag/MnO2 PHMSs. This work presents an efficient catalyst of single atom Ag incorporated MnO2 PHMSs to control air pollution.

A Photocatalytic Rotating Disc Reactor with TiO2 Nanowire Arrays Deposited for Industrial Wastewater Treatment.

A photocatalytic rotating disc reactor (PRD-reactor) with TiO2 nanowire arrays deposited on a thin Ti plate is fabricated and tested for industrial wastewater treatment. Results indicate that the PRD-reactor shows excellent decolorization capability when tested with methyl orange (>97.5%). Advanced oxidation processes (AOP), including photocatalytic oxidation and photolytic reaction, occurred during the processing. Efficiency of the AOP increases with reduction in light absorption pathlength, which enhanced the photocatalytic reaction, as well as by increasing oxygen exposure of the wastewater thin film due to the rotating disc design. It is found that, with a small dosage of hydrogen peroxide, the mineralization efficiency of industrial biodegraded wastewater can be enhanced, with a superior mineralization of >75% total organic carbon (TOC) removal. This is due to the fact that the TiO2 photocatalysis and hydrogen peroxide processes generate powerful oxidants (hydroxyl radicals) that can strongly improve photocatalytic oxidation efficiency. Application of this industrial wastewater treatment system is benefited from the TiO2 nanowire arrays, which can be fabricated by a mild solvothermal method at 80 °C and under atmospheric pressure. Similar morphologies and microstructures are found for the TiO2 nanowire arrays deposited on a large metal Ti disc, which makes the wastewater treatment process more practical and economical.

Nitric oxide removal by wastewater bacteria in a biotrickling filter.

Nitric oxide (NO) is one of the most important air pollutants in atmosphere mainly emitted from combustion source. A biotrickling filter was designed and operated to remove NO from an air stream using bacteria extracted from the sewage sludge of a municipal sewage treatment plant. To obtain the best operation conditions for the biotrickling filter, orthogonal experiments (L9(3(4))) were designed. Inlet oxygen concentration was found to be the most significant factor of the biotrickling filter and has a significant negative effect on the system. The optimal conditions of the biotrickling filter occurred at a temperature of 40°C, a pH of 8.0 and a chemical oxygen demand of 165 mg/L in the recycled water with no oxygen in the system. The bacteria sample was detected by DNA sequencing technology and showed 93%-98% similarity to Pseudomonas mendocina. Moreover, a full gene sequencing results indicated the bacterium was a brand new strain and named as P. mendocina DLHK. This strain can transfer nitrate to organic nitrogen. The result suggested the assimilation nitrogen process in this system. Through the isotope experimental analysis, two intermediate products ((15)NO and (15)N2O) were found. The results indicated the denitrification function and capability of the biotrickling filter in removing NO.

Heterointerfaces: Unlocking Superior Capacity and Rapid Mass Transfer Dynamics in Energy Storage Electrodes.

Heterogeneous electrode materials possess abundant heterointerfaces with a localized "space charge effect", which enhances capacity output and accelerates mass/charge transfer dynamics in energy storage devices (ESDs). These promising features open new possibilities for demanding applications such as electric vehicles, grid energy storage, and portable electronics. However, the fundamental principles and working mechanisms that govern heterointerfaces are not yet fully understood, impeding the rational design of electrode materials. In this study, the heterointerface evolution during charging and discharging process as well as the intricate interaction between heterointerfaces and charge/mass transport phenomena, is systematically discussed. Guidelines along with feasible strategies for engineering structural heterointerfaces to address specific challenges encountered in various application scenarios, are also provided. This review offers innovative solutions for the development of heterogeneous electrode materials, enabling more efficient energy storage beyond conventional electrochemistry. Furthermore, it provides fresh insights into the advancement of clean energy conversion and storage technologies. This review contributes to the knowledge and understanding of heterointerfaces, paving the way for the design and optimization of next-generation energy storage materials for a sustainable future.

Next-generation magnesium-ion batteries: The quasi-solid-state approach to multivalent metal ion storage.

Mg-ion batteries offer a safe, low-cost, and high-energy density alternative to current Li-ion batteries. However, nonaqueous Mg-ion batteries struggle with poor ionic conductivity, while aqueous batteries face a narrow electrochemical window. Our group previously developed a water-in-salt battery with an operating voltage above 2 V yet still lower than its nonaqueous counterpart because of the dominance of proton over Mg-ion insertion in the cathode. We designed a quasi-solid-state magnesium-ion battery (QSMB) that confines the hydrogen bond network for true multivalent metal ion storage. The QSMB demonstrates an energy density of 264 W·hour kg-1, nearly five times higher than aqueous Mg-ion batteries and a voltage plateau (2.6 to 2.0 V), outperforming other Mg-ion batteries. In addition, it retains 90% of its capacity after 900 cycles at subzero temperatures (-22°C). The QSMB leverages the advantages of aqueous and nonaqueous systems, offering an innovative approach to designing high-performing Mg-ion batteries and other multivalent metal ion batteries.

Effects of building aspect ratio, diurnal heating scenario, and wind speed on reactive pollutant dispersion in urban street canyons.

A photochemistry coupled computational fluid dynamics (CFD) based numerical model has been developed to model the reactive pollutant dispersion within urban street canyons, particularly integrating the interrelationship among diurnal heating scenario (solar radiation affections in nighttime, daytime, and sun-rise/set), wind speed, building aspect ratio (building-height-to-street-width), and dispersion of reactive gases, specifically nitric oxide (NO), nitrogen dioxide (NO2) and ozone (O3) such that a higher standard of air quality in metropolitan cities can be achieved. Validation has been done with both experimental and numerical results on flow and temperature fields in a street canyon with bottom heating, which justifies the accuracy of the current model. The model was applied to idealized street canyons of different aspect ratios from 0.5 to 8 with two different ambient wind speeds under different diurnal heating scenarios to estimate the influences of different aforementioned parameters on the chemical evolution of NO, NO2 and O3. Detailed analyses of vertical profiles of pollutant concentrations showed that different diurnal heating scenarios could substantially affect the reactive gases exchange between the street canyon and air aloft, followed by respective dispersion and reaction. Higher building aspect ratio and stronger ambient wind speed were revealed to be, in general, responsible for enhanced entrainment of O3 concentrations into the street canyons along windward walls under all diurnal heating scenarios. Comparatively, particular attention can be paid on the windward wall heating and nighttime uniform surface heating scenarios.

Ni-Fe Layered Double Hydroxide Nanosheets Supported on Exfoliated Graphite for Efficient Urea Oxidation in Direct Urea Fuel Cells.

Urea-rich wastewater can cause serious eutrophication problem to the water environment. On the other hand, urea is a potential fuel with high energy density, which can be effectively utilized by direct urea fuel cell. In this work, exfoliated graphite (EG) with high surface area and electrical conductivity was obtained by microwave irradiation, which was used to support the Ni-Fe layered double hydroxide (LDH), leading to a highly efficient and low-cost urea oxidation catalyst. Compared with commercial RuO2 , the as-prepared Ni-Fe LDH/EG exhibited a lower onset potential of 1.25 V vs. reversible hydrogen electrode as well as a lower Tafel slope of 44 mV dec-1 . The catalyst durability was also proved to be excellent. The optimized Ni/Fe molar ratio was confirmed to be 3 : 1, while the most suitable catalyst/EG ratio was 3 : 50. When applied in a dual-electrolyte direct urea fuel cell, the peak power density reached 12 mW cm-2 , and the long-term discharge was also stable with negligible voltage loss at 10 mA cm-2 for 3 h. Such a low-cost and efficient urea oxidation catalyst can be widely utilized in future direct urea fuel cells, which achieve wastewater treatment and renewable electricity generation at the same time.

Catalytic ozonation of VOCs at low temperature: A comprehensive review.

VOCs abatement has attracted increasing interest because of the detrimental effects on both atmospheric environment and human beings of VOCs. The assistance of ozone has enabled efficient VOCs removal at low temperature. Thereby, catalytic ozonation is considered as one of the most feasible and effective methods for VOCs elimination. This work systematically reviews the emerging advances of catalytic ozonation of different VOCs (i.e., aromatic hydrocarbons, oxygenated VOCs, chlorinated VOCs, sulfur-containing VOCs, and saturated alkanes) over various functional catalysts. General reaction mechanism of catalytic ozonation including both Langmuir-Hinshelwood and Mars-van-Krevelen mechanisms was proposed depending on the reactive oxygen species involving the reactions. The influence of reaction conditions (water vapor and temperature) is fully discussed. This review also introduces the enhanced VOCs oxidation via catalytic ozonation in the ozone-generating systems including plasma and vacuum ultraviolet. Lastly, the existing challenges of VOCs catalytic ozonation are presented, and the perspective of this technology is envisioned.

Constructing an ohmic junction of copper@ cuprous oxide nanocomposite with plasmonic enhancement for photocatalysis.

A novel ohmic junction Cu@Cu2O photocatalyst with plasmonic enhancement had been successfully obtained by NaBH4 reduction, which exhibited excellent photocatalytic performance for the catalytic oxidation of nitric oxide (NO) and catalytic reduction of carbon dioxide (CO2). The desirable photocatalytic performance can be ascribed to the efficient interfacial charge separation and the high light absorption capacity induced by localized surface plasmon resonance (LSPR) of Cu nanoparticles in the Cu@Cu2O photocatalyst. To better understand why this catalyst has satisfying stability and photocatalytic performance for the removal of NO and photocatalytic reduction of CO2, a series of characterization methods was used to investigate the physical composition, structure, and optical properties of the sample in detail. Then, the separation efficiency of photogenerated carriers of the catalyst was investigated by time-resolved photoluminescence spectra, electrochemical impedance spectroscopy, and photocurrent density. In addition, Finite-Different-Time-Domain (FDTD) simulation and Cambridge Serial Total Energy Package (CASTEP) were adopted to confirm the Cu-induced LSPR effect, the electric field enhancement, and the band structure of the catalyst, respectively. Moreover, the ohmic junction structure has been verified by the calculation results of work function and charge density difference. Finally, a reasonable plasmonic ohmic junction photocatalytic mechanism was proposed and verified by the simulation and experiments.

An efficient process for aromatic VOCs degradation: Combination of VUV photolysis and photocatalytic oxidation in a wet scrubber.

The elimination of volatile organic compounds (VOCs) via vacuum ultraviolet (VUV) photolysis is greatly limited by low removal efficiency and gaseous byproducts generation, while photocatalytic oxidation of VOCs suffers from catalytic deactivation. Herein, a coupled process of gaseous VUV photolysis with aqueous photocatalytic oxidation with P25 as the catalyst was firstly proposed for efficient aromatic VOCs removal (VUV/P25). The removal efficiency of toluene reached 86.2% in VUV/P25 process, but was only 33.6% and 58.1% in alone gaseous VUV photolysis and aqueous ultraviolet photocatalytic oxidation (UV/P25) process, respectively. Correspondingly, the outlet CO2 concentration in VUV/P25 process reached 132 ppmv. Toluene was firstly destructed by high-energy photons generated from gaseous VUV photolysis, resulting in its incomplete oxidation to form soluble intermediates including acids, aldehydes, esters. These soluble intermediates would be further degraded and mineralized into CO2 in subsequent aqueous UV/P25 process. Notably, the concentrations of intermediates in VUV/P25 were much lower than those in VUV photolysis, indicating the synergy effect of VUV photolysis and UV/P25 process. The stability tests proved that VUV/P25 process maintained an excellent toluene degradation performance and P25 did not suffer from catalytic deactivation. In addition to toluene, the VUV/P25 system also achieved the efficient and sustainable degradation of styrene and chlorobenzene, suggesting its good application prospect in industrial VOCs treatment. This study proposes an efficient and promising strategy for deep oxidation of multiple aromatic VOCs in industries.

High-Performance MnO2 /Al Battery with In Situ Electrochemically Reformed Alx MnO2 Nanosphere Cathode.

Aqueous Al-ion battery (AAIB) is regarded as a promising candidate for large-scale energy storage systems due to its high capacity, high safety, and low cost, with MnO2 proved to be a high-performance cathode. However, the potential commercial application of this type of battery is plagued by the frequent structural collapse of MnO2 . Herein, an in situ, electrochemically reformed, urchin-like Alx MnO2 cathode is developed for water-in-salt electrolyte-based AAIBs. Benefiting from its unique α-MnO2 coated Mn2 AlO4 structure, a high Al ion storage capacity is achieved together with a high discharge voltage plateau of 1.9 V by reversible MnO2 electrolysis. Consequently, the battery exhibits a high specific capacity of 285 mAh g-1 and a high energy density of 370 Wh kg-1 at a high current density of 500 mA g-1 . Improved stability with record capacity retention is also obtained at an ultrahigh current density of 5 A g-1 after 500 cycles. Such a high-capacity and high-stability Alx MnO2 cathode would pave the way for in situ electrochemical transformation of cathode design and thus boost the practical application of AAIBs.

Insights into the photocatalysis mechanism of the novel 2D/3D Z-Scheme g-C3N4/SnS2 heterojunction photocatalysts with excellent photocatalytic performances.

A novel 2D/3D Z-scheme g-C3N4/SnS2 photocatalyst was successfully fabricated via self-assembly forming 3D flower-like SnS2 microspheres on the surface of the 2D g-C3N4 nanosheets. The photocatalytic performances of the samples were systematically explored through catalytic reduction of Cr6+ and oxidation of Bisphenol S (BPS) under the illumination of visible light, and the photocatalytic degradation pathway of BPS was also proposed based on the degradation products confirmed by GCMS. Among the as-prepared samples, 0.4-g-C3N4/SnS2 exhibited the most efficient photocatalytic performances, and the apparent quantum efficiency (QE) for the removal of Cr6+ could achieve 30.3 %, which is 2.8 times higher than that of the SnS2. The enhancing photocatalytic activities originated from the efficient interfacial charge migration and separation obtained in g-C3N4/SnS2, which was firstly verified via the photoluminescence spectra, time-resolved photoluminescence spectra and photoelectrochemical characterizations. Importantly, the DFT calculated shows that the band distribution of the g-C3N4/SnS2 sample is staggered near the forbidden, which can facilitate the efficient interfacial charge migration and separation as well as result in the improvement of the catalytic activity. Finally, we put forward a more reasonable Z-scheme charge transfer mechanism, it was verified by analysing the results of free radical scavenging tests, EPR experiments and theoretical calculations.

Study on the Photocatalysis Mechanism of the Z-Scheme Cobalt Oxide Nanocubes/Carbon Nitride Nanosheets Heterojunction Photocatalyst with High Photocatalytic Performances.

An efficient Z-scheme Co3O4/g-C3N4 heterojunction photocatalyst was developed via in-situ forming Co3O4 nanocubes on the g-C3N4 nanosheet in the hydrothermal process. The obtained photocatalyst exhibited high photocatalytic activity for the visible-light-driven catalytic reduction of Cr(VI) and catalytic oxidation of tetracycline (TC). Among the as-synthesized catalysts, Co3O4/g-C3N4-0.04 (the mass ratio of g-C3N4 to Co3O4 is 0.04) sample exhibits the most efficient catalytic activities. The photocatalytic reduction and photocatalytic oxidation efficiencies of Co3O4/g-C3N4-0.04 can obtain 81.3 and 92.6 %, respectively. Moreover, the TC is mineralized in the course of photocatalytic degradation, 72.2% of TOC is removed from the reaction system. In addition, the apparent quantum efficiency for the removal of Cr(VI) was also obtained and the the Co3O4/g-C3N4-0.04 could achieve the highest apparent quantum efficiency among the samples. The enhancing photocatalytic activities originated from the efficient interfacial charge migration and separation obtained in Co3O4/g-C3N4-0.04, which is preliminarily confirmed by the photoluminescence spectra, time-resolved photoluminescence spectra and the photoelectrochemical characterizations. Finally, we speculate that the Co3O4/g-C3N4 heterostructures follow a more reasonable Z-scheme charge transfer in this study, which is confirmed by analyzing the results of electron paramagnetic resonance, radical scavenging experiments, and theoretical calculations.

Z-scheme Au decorated carbon nitride/cobalt tetroxide plasmonic heterojunction photocatalyst for catalytic reduction of hexavalent chromium and oxidation of Bisphenol A.

Au/g-C3N4/Co3O4 plasmonic heterojunction photocatalyst was successfully prepared by in-situ forming Co3O4 nanocubes on the Au/g-C3N4 nanosheets. The catalytic activities of the photocatalysts were systematically studied through the catalytic reduction of hexavalent chromium (Cr6+) and oxidation of Bisphenol A (BPA) under visible light irradiation, while according to the degradation products determined by GC-MS, the catalytic degradation pathway of BPA was proposed. 4Au/g-C3N4/Co3O4 sample exhibits the most efficient catalytic activities, and the photocatalytic reduction and photocatalytic oxidation efficiencies can obtain 85.6% and 90.3%, respectively. The main reasons of the enhancing catalytic performance are the high absorption capability to visible light generated by localized surface plasmon resonance and the effective interface charge separation. Finally, we speculated that the Au/g-C3N4/Co3O4 sample followed Z-scheme charge transfer mechanism in this study, which is verified by the analysis of experiment and theoretical calculation results.

Impacts of environmental factors on urban heating.

This study investigated the impact of important environmental variables (i.e., wind speed, solar radiation and cloud cover) on urban heating. Meteorological parameters for fifteen years (from 1990 to 2005), collected at a well developed and densely populated commercial area (Tsim Sha Tsui, Hong Kong), were analyzed in details. Urban heat island intensity (UHII), a well known indicator of urban heating, has been determined as the spatially averaged air-temperature difference between Tsim Sha Tsui and Ta Kwu Ling (a thinly populated rural area with lush vegetation). Results showed that the UHII and cloud cover have increased by around 9.3% and 4%, respectively, whereas the wind speed and solar radiation have decreased by around 24% and 8.5%, respectively. The month of December experienced the highest UHII (10.2 degrees C) but the lowest wind speed (2.6 m/sec) and cloud cover (3.8 oktas). Conversely, the month of April observed the highest increases in the UHII (over 100%) and the highest decreases in wind speed (over 40%) over fifteen years. Notably, the increases in the UHII and reductions in the wind speed were the highest during the night-time and early morning. Conversely, the intensity of solar radiation reduced while the intensity of urban cool island (UCII) increased during solar noon-time. Results demonstrated strong negative correlation between the UHII and wind speed (coefficient of determination, R2 = 0.8) but no negative correlation between UCII and solar radiation attenuation. A possible negative correlation between UHII and cloud cover was investigated but could not be substantiated.