Efficient Photoreduction of CO2 to CO with 100% Selectivity by Slowing Down Electron Transport.

It remains challenging to obtain a single product in the gas-solid photocatalytic reduction of CO2 because CO and CH4 are usually produced simultaneously. This study presents the design of the I-type nested heterojunction TiO2/BiVO4 with controllable electron transport by modulating the TiO2 component. This study demonstrates that slowing electron transport could enable TiO2/BiVO4-4 to generate CO with 100% selectivity. In addition, modifying TiO2/BiVO4-4 by loading a Cu single atom further increased the CO product yield by 3.83 times (17.33 µmol·gcat-1·h-1), while maintaining 100% selectivity for CO. Characterization and density functional theory (DFT) calculations revealed that the selectivity was mainly determined by the electron transport of the support, whereas CO2 was efficiently adsorbed and activated by the Cu single atom. Such a two-step regulation strategy of combining heterojunction with single atom enhances the possibility of simultaneously obtaining high selectivity and high yield in the photocatalytic reduction of CO2.

Identifying the Growth Status of Hydroponic Lettuce Based on YOLO-EfficientNet.

Hydroponic lettuce was prone to pest and disease problems after transplantation. Manual identification of the current growth status of each hydroponic lettuce not only consumed time and was prone to errors but also failed to meet the requirements of high-quality and efficient lettuce cultivation. In response to this issue, this paper proposed a method called YOLO-EfficientNet for identifying the growth status of hydroponic lettuce. Firstly, the video data of hydroponic lettuce were processed to obtain individual frame images. And 2240 images were selected from these frames as the image dataset A. Secondly, the YOLO-v8n object detection model was trained using image dataset A to detect the position of each hydroponic lettuce in the video data. After selecting the targets based on the predicted bounding boxes, 12,000 individual lettuce images were obtained by cropping, which served as image dataset B. Finally, the EfficientNet-v2s object classification model was trained using image dataset B to identify three growth statuses (Healthy, Diseases, and Pests) of hydroponic lettuce. The results showed that, after training image dataset A using the YOLO-v8n model, the accuracy and recall were consistently around 99%. After training image dataset B using the EfficientNet-v2s model, it achieved excellent scores of 95.78 for Val-acc, 94.68 for Test-acc, 96.02 for Recall, 96.32 for Precision, and 96.18 for F1-score. Thus, the method proposed in this paper had potential in the agricultural application of identifying and classifying the growth status in hydroponic lettuce.

Triggering photocatalytic performance of La2CoxMn2-xO6 via heat activation.

The La-based perovskite (LaBO3) exhibits excellent optical properties. However, its valence band (VB) potential is not sufficiently positive to reach the oxidation potential required for the cleavage of chemical bonds (such as benzylic C-H), limiting its application in photocatalysis. Herein, we report the unconventional effects of heat activation on the reduction of the dissociation energy of benzylic C-H and aqueous H-O, thereby triggering the photocatalytic activity of La2CoxMn2-xO6 perovskites. Additionally, we demonstrate that photocatalysis is the main contributor to substrate conversion in the selective oxidation of toluene and reduction of CO2. Particularly, La2Co1.5Mn0.5O6 shows excellent performance with a product yield of 550.00 mmol gcat-1 and a toluene conversion of 22,866.67 µmol gcat-1 h-1. To the best of our knowledge, this is the highest reported product yield for the selective oxidation of benzylic C-H bond of toluene. Our findings provide insight into the specific role of heat activation in photocatalysis, which is crucial for breaking and overcoming the VB barrier to realize challenging reactions.

Efficient Photo-Assisted Thermal Selective Oxidation of Toluene Using N-Doped TiO2.

Selective oxidation of toluene is a key reaction to produce high value-added products but remains a big challenge. In this study, we introduce a nitrogen-doped TiO2 (N-TiO2) catalyst to create more Ti3+ and oxygen vacancy (OV), which act as active sites for selective oxidation of toluene via activating O2 to superoxide radical (•O2-). Interestingly, the resulting N-TiO2-2 exhibited an outstanding photo-assisted thermal performance with a product yield of 209.6 mmol·gcat-1 and a toluene conversion of 10960.0 µmol·gcat-1·h-1, which are 1.6 and 1.8 times greater than those obtained under thermal catalysis. We showed that the enhanced performance under photo-assisted thermal catalysis was attributed to more active species generation by making full use of photogenerated carriers. Our work suggests a viewpoint to apply a noble-metal-free TiO2 system in the selective oxidation of toluene under solvent-free conditions.

Insights into Chlorobenzene Catalytic Oxidation over Noble Metal Loading {001}-TiO2: The Role of NaBH4 and Subnanometer Ru Undergoing Stable Ru0↔Ru4+ Circulation.

Catalytic combustion of ubiquitous chlorinated volatile organic compounds (CVOCs) encounters bottlenecks regarding catalyst deactivation by chlorine poisoning and generation of toxic polychlorinated byproducts. Herein, Ru, Pd, and Rh were loaded on {001}-TiO2 for thermal catalytic oxidation of chlorobenzene (CB), with Ru/{001}-TiO2 representing superior reactivity, CO2 selectivity, and stability in the 1000 min on-stream test. Interestingly, both acid sites and reactive active oxygen species (ROS) were remarkably promoted via adding NaBH4. But merely enhancing these active sites of the catalyst in CVOC treatment is insufficient. Continuous deep oxidation of CB with effective Cl desorption is also a core issue successfully tackled through the steady Ru0↔Ru4+ circulation. This circulation was facilitated by the observed higher subnanometer Ru dispersion on {001}-TiO2 than the other two noble metals that was supported by single atom stability DFT calculation. Nearly 88 degradation products in off-gas were detected, with Ru/{001}-TiO2 producing the lowest polychlorinated benzene byproducts. An effective and sustainable CB degradation mechanism boosted by the cooperation of NaBH4 enhanced active sites and Ru circulation was proposed accordingly. Insights gained from this study open a new avenue to the rational design of promising catalysts for the treatment of CVOCs.

High-spatial-resolution VOCs emission from the petrochemical industries and its differential regional effect on soil in typical economic zones of China.

Volatile organic compounds (VOCs) are toxic to the ecological environment. The emission of VOCs into the atmosphere has already caused attention. However, few studies focus on their regional effects on soil. As a major VOCs source in China, research on the effect of petrochemical industry on the environment is urgent and essential for regional control and industrial layout. This study established national VOCs emission inventory of five petrochemical sub-industries and spatial distribution based on consumption of raw material or products' yield and 28,888 factories. The VOCs emissions showed continuously increasing trend from 2008 to 2019, with cumulative 1.83 × 107 t, wherein these from rapid economic development zones accounted for 66.10%. The detected concentrations of VOCs in various industries combined with meteorological parameters were used in Resistance Model to quantify regional dry deposition. Higher concentrations of 111 VOC species were 238.27, 260.01, 207.54 µg·m-3 from large-scale enterprises for crude oil and natural gas extraction, oil processing, synthetic rubber and resin, leading to higher deposition ratios of 0.81%-0.94%, 0.70%-0.81%, 1.50%-1.75% in rapid economic development zones, respectively. The regional climate condition played a dominant role. Annual VOCs dry deposition amount in rapid economic development zones was calculated to be totally 6.38 × 103 t using obtained deposition ratios and emissions, with 3.21 × 103 t in Bohai Economic Rim (BER), 2.42 × 103 t in Yangtze River Economic Belt (YREB), 748.43 t in Pearl River Delta (PRD). Generally, crude oil and natural gas extraction, oil processing, synthetic rubber and resin contributed 13.09%, 57.77% and 29.14%, respectively. The proportion of synthetic rubber and resin for dry deposition increased by 5.04%-18.81% compared with VOCs emissions in BER and YREB. In contrast, it declined from 45.52% for emission to 29.86% for deposition due to absolute dominance of small-scale enterprises in PRD. Overall, VOCs control from oil processing was significant, especially in BER.

Effects of Inlet Gas Allocations on Performance of an Active Drainage Flow Field Proton Exchange Membrane Fuel Cell.

In developing a proton exchange membrane fuel cell, a high current density is encountered, thus requiring a novel flow field with great drainage performance. Our previous study proposed a novel compound flow field called an active drainage flow field with three inlets, which has an excellent output and drainage performance. Furthermore, the influence of muti-inlet reactant gas allocation on the three inlets is discussed in this study. The results showed that the small mass flow in the active drainage (AD) channel causes a waste of active area, while the large mass flow in the AD channel causes under-ribs convection. Considering the output and drainage performance, the 15% AD mass flow case shows the best performance under the high relative humidity investigation.

Experimental and Numerical Study of Proton Exchange Membrane Fuel Cells with a Novel Compound Flow Field.

Excess water seriously affects the performance and lifetime of proton exchange membrane fuel cells (PEMFCs). This study proposes a novel compound flow field, which is named the active drainage flow field (ADFF). The new design enhances the drainage performance by under-ribs flow, while the output performance is very close to that of the conventional serpentine flow field (CSFF). Additionally, the ADFF bipolar plate has been taken as a cathode while retaining CSFF as an anode; the combination shows a good output performance under high relative humidity. The peak power density has reached to 0.59 W/cm2, which is 13% higher than that of the CSFF.

Recent advances in the removal of persistent organic pollutants (POPs) using multifunctional materials:a review.

Persistent organic pollutants (POPs) have gained heightened attentions in recent years owing to their persistent property and hazard influence on wild life and human beings. Removal of POPs using varieties of multifunctional materials have shown a promising prospect compared with conventional treatments. Herein, three main categories, including thermal degradation, electrochemical remediation, as well as photocatalytic degradation with the use of diverse catalytic materials, especially the recently developed prominent ones were comprehensively reviewed. Kinetic analysis and underlying mechanism for various POPs degradation processes were addressed in detail. The review also systematically documented how catalytic performance was dramatically affected by the nature of the material itself, the structure of target pollutants, reaction conditions and treatment techniques. Moreover, the future challenges and prospects of POPs degradation by means of multiple multifunctional materials were outlined accordingly. Knowing this is of immense significance to enhance our understanding of POPs remediation procedures and promote the development of novel multifunctional materials.

Environmental impact and health risk assessment of volatile organic compound emissions during different seasons in Beijing.

Volatile organic compounds (VOCs) are major contributors to air pollution. Based on the emission characteristics of 99 VOCs that daily measured at 10 am in winter from 15 December 2015 to 17 January 2016 and in summer from 21 July to 25 August 2016 in Beijing, the environmental impact and health risk of VOC were assessed. In the winter polluted days, the secondary organic aerosol formation potential (SOAP) of VOC (199.70 ± 15.05 µg/m3) was significantly higher than that on other days. And aromatics were the primary contributor (98.03%) to the SOAP during the observation period. Additionally, the result of the ozone formation potential (OFP) showed that ethylene contributed the most to OFP in winter (26.00% and 27.64% on the normal and polluted days). In summer, however, acetaldehyde was the primary contributor to OFP (22.00% and 21.61% on the normal and polluted days). Simultaneously, study showed that hazard ratios and lifetime cancer risk values of acrolein, chloroform, benzene, 1,2-dichloroethane, acetaldehyde and 1,3-butadiene exceeded the thresholds established by USEPA, thereby presenting a health risk to the residents. Besides, the ratio of toluene-to-benzene indicated that vehicle exhausts were the main source of VOC pollution in Beijing. The ratio of m-/p-xylene-to-ethylbenzene demonstrated that there were more prominent atmospheric photochemical reactions in summer than that in winter. Finally, according to the potential source contribution function (PSCF) results, compared with local pollution sources, the spread of pollution from long-distance VOCs had a greater impact on Beijing.

Photochemical reactions of 1,3-butadiene with nitrogen oxide in different matrices: Kinetic behavior, humidity effect, product and mechanisms.

Understanding the photochemical reaction process between VOCs and co-pollutants in the troposphere is crucial for controlling the haze. The photochemical reactions of 1,3-butadiene (1,3-BD) with NO were carried out at 308 K for up to 96 h in clean air with various relative humidity (RH) values, and actual haze atmosphere. In the haze, the representative pseudo-first-order kinetic rate constants of the 1,3-BD-NO system was 1.53 time higher than those in dry clean air. The effect of the RH (0%-80%) on the conversion behavior of the 1,3-BD-NO system in clean air was studied, revealing that increasing RH promoted the photochemical reaction in the low range of 0%-40% but retarded it in the high range of 40%-80%. Interestingly, OH radicals were directly detected under different RH values, and the strongest OH signal was obtained at an RH of 40%. Multiple macromolecular products with carbon numbers of 10-36 were identified. Unexpectedly, richer products and extended unsaturation range were detected at an RH of 40% than 0%. The photochemical products were also analyzed using ion chromatography. A reaction mechanism was proposed from the detected NO2, O3, OH, HNO2, HNO3, organic acids and macromolecular products.

An investigation into the role of VOCs in SOA and ozone production in Beijing, China.

In recent years, PM2.5 and O3 pollutions are prevalent in the atmosphere in Beijing. The study on pollution characteristics of VOC, which are important precursors of O3 and secondary organic aerosols (SOA) contributing PM2.5, is of great significance for providing a reference to guide its reduction policy formulation. Herein, the seasonal variation of atmospheric VOCs and meteorological conditions at the sampling frequency of 1 time per hour were continuously measured from March 2016 to January 2017 in Beijing. Using the collected data combined with multiple models, the role of VOCs in SOA and O3 production was investigated. Alkanes were the most abundant species, contributing 54.1-64.7% of the total VOC concentration for four seasons, followed by aromatics, alkenes and acetylene. The SOA potential (SOAP) was highest in winter at 2885.1 µg m-3, followed by autumn, spring and summer. Aromatics were the main contributors to SOAP, accounting for ~98.2% of the total SOAP during the entire observation period. The empirical kinetic modeling approach results showed that O3 production featured the VOC-limited regime in Beijing. Alkenes and aromatics were major contributors to O3 formation potential (OFP), accounting for 33.1-45.6% and 27.2-45.2%, respectively, particularly ethylene and m,p-xylene. Positive matrix factorization results indicated that motor vehicle exhaust was still the largest local source of VOCs, but its proportion was considerably reduced. The potential source contribution function results revealed that regional transport sources of VOC pollution in Beijing mainly came from the northwest and southern areas. Thus, to control PM2.5 and O3 pollution in Beijing, the restriction of alkenes and aromatics emission, accompanied by regional cooperation combined with local control, is essential.

Thermal catalytic degradation of α-HBCD, ß-HBCD and γ-HBCD over Fe3O4 micro/nanomaterial: Kinetic behavior, product analysis and mechanism hypothesis.

The new persistent organic pollutant (POP), 1,2,5,6,9,10-hexabromocyclododecane (HBCD), has been widely detected in various environmental media and proved to be biotoxic. However, the research on catalytic degradation of HBCD is in its infancy. Herein, we examined the degradation of α-HBCD, ß-HBCD and γ-HBCD, over Fe3O4 micro/nanomaterial at 200 °C. The pseudo-first-order kinetic rate constants were in the range of 0.04-0.15 min-1, with half-life values of 5-19 min. γ-HBCD is slightly less stable than ß-HBCD, but both of them readily convert into α-HBCD, as consistent with the Gibbs free energies of isomers themselves. The four products containing pentabromocyclododecene, two isomers of tetrabromocyclododecene and 1,5,9-cyclododecatriene were detected by conventional GC-MS. Interestingly, a high-throughput non-target product detection were performed by ESI-FT-ICR-MS, where up to 59 types of intermediate products were determined. It is tentatively proposed that different types of bromine-removed products (C12H17Br5, C12H18Br4, C12H18, C12H19Br5, C12H24 and C12H19Br5O) and cyclododecane ring-opened products (C12H19Br7, C12H20Br6O and C12H20Br6) form via elimination reaction, nucleophilic substitution, hydrodebromination and addition reaction. Besides, most of the products that were detected contained oxygen. The average carbon oxidation state (OSc¯) of the products indicate that the oxidation reaction is the dominant reaction type. Deep oxidation products, such as small molecular organic acids (formic, acetic, propionic, and butyric acids) and gas-phase oxidation products (CO2 and CO) were further detected by ion chromatography and GC-FID, respectively. This study might provide an alternative technique for the low-cost treatment of HBCD waste.

[Appropriate dosage of unfraction heparin and low molecular weight heparin in hemodialysis patients].

OBJECTIVE: To investigate the appropriate dose of unfraction heparin and low molecular weight heparin (LMWH) in hemodialysis patients. METHODS: Thirty-eight hemodialysis patients were enrolled and randomly allocated into four groups.The initial bolus dose for the Low-dose (LH, n = 10) and high-dose heparin (HH, n = 10) groups were 35 U/kg and 55 U/kg, respectively.The repeated maintenance dose for both groups were 10 U/kg.h and 16 U/kg.h, respectively. Fragmin were administered as single bolus (60 U/kg or 80 U/kg) at 30 minutes before hemodialysis in Low-dose LMWH(LLMWH, n = 10) and High-dose LMWH (HLMW, n = 8) group, respectively. Furthermore, the dialysis circuits in LUFH and LLMWUFH groups were primed with with 4 mg/dl heparinized saline before hemodialysis. Glass bead active clotting time (gbACT), clot rate (CR) and platelet function (PF) were examined using Sonoclot analysator at 0 h, 2 h and the end of hemodialysis at the arterial circuit and 2 h at the venous circuit. RESULTS: (1) LH and LUFH: the increase of gbACT and decrease of CR at the arterial circuit and the venous circuit at 2 h of hemodialysis were significant compared with baseline. While they recovered at the end of hemodialysis. No difference between the two groups at different time points was found, either. (2) LLMWH: No change were found in gbACT during hemodialysis. CR at the arterial circuit and the venous circuit were significantly decreased at 2 h and recovered at the end of hemodialysis. (3) LLMWUFH: gbACT at the arterial circuit was significantly increased only at 2 h of hemodialysis. CR at the arterial circuit and the venous circuit at 2 h of hemodialysis were significantly decreased and recovered when hemodialysis finished. (4) HH and HLMWH: gbACT were significantly increased and CR were rapidly decreased at both the arterial circuit and venous circuit at 2 h of hemodialysis. CONCLUSION: Low-dose heparin was effective and safe as anticoagulant in hemodialysis. Low-dose low-molecular-weight heparin was efficient in anticoagulation to some extent. However, High-dose low-molecular-weight heparin, high-dose heparin and flushing with heparinized saline may increase the risk of hemorrhage.