Metal-Based Aerogels Catalysts for Electrocatalytic CO2 Reduction.

General strategies for metal aerogel synthesis, including single-metal, transition-metal doped, multi-metal-doped, and nano-metal-doped carbon aerogel are described. In addition, the latest applications of several of the above-mentioned metal aerogels in electrocatalytic CO2 reduction are discussed. Finally, considering the possibility of future applications of electrocatalytic CO2 reduction technology, a vision for industrialization and directions that can be optimized are proposed.

How local electric field regulates C-C coupling at a single nanocavity in electrocatalytic CO2 reduction.

C-C coupling is of utmost importance in the electrocatalytic reduction of CO2, as it governs the selectivity of diverse product formation. Nevertheless, the difficulties to directly observe C-C coupling pathways at a specific nanocavity hinder the advances in catalysts and electrolyzer design for efficient high-value hydrocarbon production. Here we develop a nano-confined Raman technology to elucidate the influence of the local electric field on the evolution of C-C coupling intermediates. Through precise adjustments to the Debye length in nanocavities of a copper catalyst, the overlapping of electrical double layers drives a transition in the C-C coupling pathway at a specific nanocavity from *CHO-*CO coupling to the direct dimerization of *CO species. Experimental evidence and simulations validate that a reduced potential drop across the compact layer promotes a higher yield of CO and promotes the direct dimerization of *CO species. Our findings provide insights for the development of highly selective catalyst materials tailored to promote specific products.

Enriching the Local Concentration of CO Intermediates on Cu Cavities for the Electrocatalytic Reduction of CO2 to C2+ Products.

The electrochemical carbon-dioxide reduction reaction (CO2RR) to high-value multi-carbon (C2+) chemicals provides a hopeful approach to store renewable energy and close the carbon cycle. Although copper-based catalysts with a porous architecture are considered potential electrocatalysts for CO2 reduction to C2+ chemicals, challenges remain in achieving high selectivity and partial current density simultaneously for practical application. Here, the porous Cu catalysts with a cavity structure by in situ electrochemical-reducing Cu2O cavities are developed for high-performance conversion of CO2 to C2+ fuels. The as-described catalysts exhibit a high C2+ Faradaic efficiency and partial current density of 75.6 ± 1.8% and 605 ± 14 mA cm-2, respectively, at a low applied potential (-0.59 V vs RHE) in a microfluidic flow cell. Furthermore, in situ Raman tests and finite element simulation indicated that the cavity structure can enrich the local concentration of CO intermediates, thus promoting the C-C coupling process. More importantly, the C-C coupling should be major through the *CO-*CHO pathway as demonstrated by the electrochemical Raman spectra and density functional theory calculations. This work can provide ideas and insights into designing high-performance electrocatalysts for producing C2+ compounds and highlight the important effect of in situ characterization for uncovering the reaction mechanism.

Oxidative compensation mechanism of Fe-S synergetic inhibition of Cd activity in paddy field during flooding and drainage.

It is known that the transformation of Fe and S forms in soil affects the migration and activity of Cd, but the coordinated regulation of Cd activity by Fe and S under different redox conditions is still unclear. Here, Diffusive gradients in thin films (DGT), an in-situ monitoring technique, is used to explore the difference of the regulation of Cd activity in paddy fields with ferrihydrite (FH) and ferrihydrite coprecipitated by sulfate (FH-S) under the flooding and drainage conditions. The addition of FH-S and FH significantly reduced the activity of Cd (Dissolved, Exchanged, and CDGT-Cd). Compared with pure FH, the adsorption extent of Cd in FH was enhanced by increasing concentrations of SO42- (i.e., S/Fe ratio), which is attributed to the decrease in the crystallinity of FH by sulfate. During soil flooding, the addition of FH-S promoted the production of metal sulfide (CdS and FeS/FeS2). The activity of Cd increased after drainage, while the FH-S treatment groups delayed the release of Cd. After 30 days of drainage, the concentration of Cd in FH-S treatment groups decreased by 28.9-44.1 % compared with the control group. The fresh FeS/FeS2 is not the main adsorbent for fixing Cd, and due to the existence of oxidation compensation mechanism, the preferential oxidation of FeS/FeS2 delays the release of Cd in the drainage stage. Our study shed new light on the mechanism of Fe-S synergistic regulation of Cd and remediation of Cd-contaminated soils.

Dietary exposure estimates of 16 polycyclic aromatic hydrocarbons (PAHs) in Xuanwei and Fuyuan, counties in a high lung cancer incidence area in China.

Xuanwei and Fuyuan are located in the southwest of China and have the highest lung cancer incidence in China, possibly even highest in the world. Dietary samples were collected from these two counties and the contamination status of sixteen polycyclic aromatic hydrocarbons (PAHs) were determined. PAH components, food constituents, dietary exposure level, as well as spatial difference, were studied in the different groups. The percentage of dietary intake to total intake of PAHs was calculated and the relationship between the dietary intake of PAHs and the abnormal lung cancer incidence was primarily discussed. The results showed that rice and potatoes were the main foods of the local residents in Xuanwei and Fuyuan. The daily exposure doses of Bap (benzo[a]pyrene), total PAHs, and TEQs (toxic equivalents) based on Bap toxicity in two counties were estimated to be 458 ng d(-1), 14,532 ng d(-1), and 896 ng d(-1), respectively, which were much less than those in other cities reported previously. The lower ingestion amount of food with a relatively higher content of PAHs, such as meat and fish, could account for the lower exposure doses. PAHs with less than 4 rings occupied a high percentage of the total PAHs in food samples. The exposure doses varied significantly among different sites and even different families at the same site. Dietary exposure was not the main exposure route of PAHs at most sites. It appears that there was not a direct relationship between dietary exposure and the lung cancer incidence. However, high ratios of dietary intake to total PAHs intake (1.33%-70.61%) were found in several areas and rational diet suggestions should be given in these areas in the future.

In situ formed N-containing copper nanoparticles: a high-performance catalyst toward carbon monoxide electroreduction to multicarbon products with high faradaic efficiency and current density.

Developing efficient catalysts for electrochemical carbon monoxide reduction (ECOR) with high faradaic efficiency (FE) and current density is highly desirable. In this work, we demonstrate that the N-containing Cu nanoparticles formed in situ by the reconstruction of cuprous 7,7,8,8-tetracyanoquinodimethane possess high-performance ECOR ability. Impressively, the N-containing Cu nanoparticle catalyst presented the highest FE of 81.31% towards multicarbon products with a high commercial-grade partial current density of 162.62 mA cm-2, which is among the best of the reported Cu-based ECOR catalysts at -0.69 V versus the reversible hydrogen electrode. The retained ligand on the formed catalyst via the convenient in situ formation is crucial for the selectivity of multicarbon products. This work will arouse enthusiasm for the utilization of reconstruction features for designing ligand-containing catalysts with enhanced artificial carbon fixation ability.

A novel bone registration method using impression molding and structured-light 3D scanning technology.

Accurate bone registration is critical for computer navigation and robotic surgery. Existing registration systems are expensive, cumbersome, limited in accuracy and/or require intraoperative radiation. We recently reported a novel method of registration utilizing an inexpensive, compact, and X-ray-free structured-light 3D scanner. However, this technique is not always practical in a real surgical setting where soft tissue and blood can obstruct the continuous line-of-sight required for structured-light technology. We sought to remedy these limitations using a novel technique using rapid-setting impression molding to capture bone surface features and scan the undersurface of the mold with a structured-light scanner. The photonegative of this mold is compared to the preoperative computed tomography (CT)-scan to register the bone. A registration accuracy study was conducted on 36 CT-scanned femur sawbones, simulating typical exposure in hip/knee arthroplasty and bone tumor surgery. A cadaver experiment was also conducted to evaluate the feasibility of using the impression molding in a more realistic operating room setting. The registration accuracy of the proposed technique was 0.50 ± 0.19 mm. This was close to the reported accuracy of 0.43 ± 0.18 mm using a structured-light scanner without impression molding (p = 0.085). In comparison, historical values for "paired-point" and intraoperative CT image-based registration methods currently used in modern robotic/computer-navigation systems were 0.68 ± 0.14 mm (p = 0.004) and 0.86 ± 0.38 mm, respectively. The registration accuracy of the cadaver experiment was consistent with that of sawbone experiments. Although future studies are needed to extend to human subjects, this study shows that the impression molding method can produce comparable or better registration accuracy than the existing techniques.

Hierarchical S-modified Cu porous nanoflakes for efficient CO2 electroreduction to formate.

Electrochemical reduction of CO2 into liquid fuels is a promising approach to achieving a carbon-neutral energy cycle but remains a great challenge due to the lack of efficient catalysts. Here, the hierarchical architectures assembled by ultrathin and porous S-modified Cu nanoflakes (Cu-S NFs) are designed and constructed as an efficient electrocatalyst for CO2 conversion to formate with high partial current density. Specifically, when integrated into a gas diffusion electrode in a flow cell, Cu-S NFs are capable of delivering the ultrahigh formate current density up to 404.1 mA cm-2 with a selectivity of 89.8%. Electrochemical tests and theoretical calculations indicate that the superior performance of the designed catalysts may be attributed to the unique structure, which can provide abundant active sites, fast charge transfer, and highly active edge sites.

Cadmium uptake reduction in paddy rice with a combination of water management, soil application of calcium magnesium phosphate and foliar spraying of Si/Se.

A field experiment with 24 different treatments was carried out to study the effects of a combination of water management (WM), soil application of calcium magnesium phosphate (CMP), and foliar spraying of Si/Se on Cd uptake by paddy rice (Teyou 524). The water management modes included W1 (conventional water management) and W2 (flooding during the whole growth period). The application of CMP included P1 (1800 kg·hm-2) and P2 (3000 kg·hm-2). The leaf spraying regulations included LS (2.0 mmol·L-1 Na2SiO3), LX (25 µmol·L-1 Na2SeO3), and LSX (1.0 mmol·L-1 Na2SiO3 and 12.5 µmol·L-1 Na2SeO3). The results indicated that, compared to the control (W1), flooding and CMP reduced soil exchangeable Cd by 10.3, 21.5, 32.2, 27.6 and 36.9% under conditions of W2, P1, P2, W2P1 and W2P2, respectively; but the grain yield was reduced under W2 condition. Some individual treatments, including W2, P1, P2, LS, LX, and LSX, could reduce Cd concentration in the grain by 23.1-60.3%; but the combined regulations could reduce grain Cd concentrations up to 79.5%. Only the combined mode of CMP and leaf spraying of Si/Se could control grain Cd concentration below the Chinese National Food Safety Standard (0.2 mg·kg-1). Combined modes of fertilizer application (W2 and CMP) and foliar spraying (Si/Se), including W2P2LS, W2P2LX, W2P2LSX, were the most effective in reducing the Cd transport coefficients of both root-to-straw (RS) and straw-to-seed (SS). Considering Cd concentration in grain, treatments W2P2LS and W2P2LSX were the most effective ones, which could reduce Cd concentrations to 0.090 mg·kg-1 and 0.089 mg·kg-1 in grain, respectively. These results demonstrated that combined manipulation of the root zone (W2 and CMP) and foliar spraying (Si/Se) can effectively reduce grain Cd concentrations in rice.

Insights on forming N,O-coordinated Cu single-atom catalysts for electrochemical reduction CO2 to methane.

Single-atom catalysts (SACs) are promising candidates to catalyze electrochemical CO2 reduction (ECR) due to maximized atomic utilization. However, products are usually limited to CO instead of hydrocarbons or oxygenates due to unfavorable high energy barrier for further electron transfer on synthesized single atom catalytic sites. Here we report a novel partial-carbonization strategy to modify the electronic structures of center atoms on SACs for lowering the overall endothermic energy of key intermediates. A carbon-dots-based SAC margined with unique CuN2O2 sites was synthesized for the first time. The introduction of oxygen ligands brings remarkably high Faradaic efficiency (78%) and selectivity (99% of ECR products) for electrochemical converting CO2 to CH4 with current density of 40 mA·cm-2 in aqueous electrolytes, surpassing most reported SACs which stop at two-electron reduction. Theoretical calculations further revealed that the high selectivity and activity on CuN2O2 active sites are due to the proper elevated CH4 and H2 energy barrier and fine-tuned electronic structure of Cu active sites.

Clinical Validation of Rapid Gout Detection Method and Kit.

Gout is an inflammatory arthritis, which causes intense, acute pain due to the buildup of uric acid crystals in synovial fluid. The gold standard for gout diagnosis consists of synovial fluid analysis by polarized light microscopy, which is costly, time-intensive, and technique-dependent, therefore meriting a more efficient, inexpensive, and accessible method for diagnosis. We previously developed and validated a novel colorimetric gout detection method and device based on the reduction of silver nitrate by uric acid; here, we clinically validated our method and device using arthroscopically obtained synovial fluid samples from gout patients. We successfully identified uric acid crystals in clinical samples via our colorimetric method, visualized uric acid crystals in synovial fluid via handheld microscopy, and determined that silver nitrate stain did not interfere with the microscopic visualization of uric acid crystals necessary for diagnosis. We also developed and validated a method of processing turbid clinical samples for use in our device to prevent the obscuration of uric acid crystals by suspended material. Our method and device will clinically facilitate the immediate colorimetric diagnosis of gout and the subsequent bedside visualization of uric acid crystals in both ideal and turbid synovial fluid samples, allowing for a point-of-care diagnosis of gout.

Assessment of polycyclic aromatic hydrocarbons (PAHs) pollution in soil of suburban areas in Tianjin, China.

Soil contamination with polycyclic aromatic hydrocarbons is an increasing problem and has aroused more and more concern in many countries, including China. In this study, representative soil samples (n = 87) of suburban areas in Tianjin (Xiqing, Dongli, Jinnan, Beichen) were evaluated for 16 polycyclic aromatic hydrocarbons. Surface soil samples were air-dried and sieved. Microwave assisted extraction was used for polycyclic aromatic hydrocarbons preparation prior to analysis with gas chromatography-mass spectrometry. The total concentrations of tested polycyclic aromatic hydrocarbons in Xiqing, Dongli, Jinnan, Beichen ranged in 58.5-2,748.3, 36.1-6,734.7, 58.5-4,502.5, 29.7-852.5 ng/g and the averages of total concentration of polycyclic aromatic hydrocarbons were 600.5, 933.6, 640.8, 257.3 ng/g, respectively. Spatial variation of polycyclic aromatic hydrocarbons in soil was illustrated; Pollution status and comparison to other cities were also investigated. Serious polycyclic aromatic hydrocarbons soil pollution was found in Dongli district, on the contrary, Bap in most sites in Beichen did not exceed relative standards and most sites in Beichen should be classified as non-contaminated soil. Principal component analysis was used to identify the possible sources of different districts. It turned out that coal combustion still was the most important sources in three districts except Beichen. Coking, traffic, cooking, biomass combustion also accounted for polycyclic aromatic hydrocarbons pollution to certain extent in different districts. These data can be further used to assess the health risk associated with soils polluted with polycyclic aromatic hydrocarbons and help local government find proper way to reduce polycyclic aromatic hydrocarbons pollution in soils.

Levels, spatial distribution and possible sources of heavy metals contamination of suburban soils in Tianjin, China.

Representative soil samples (n = 86) of suburban areas in Tianjin (Xiqing, Dongli, Jinnan, Beichen) were evaluated for heavy metals. The results showed that the average concentration of Cr, Cu, Zn, As, Cd, Pb and Hg in soil of Tianjin suburban was 101.0, 67.0, 100.6, 9.5, 0.49, 52.5 and 0.97 mg/kg, respectively. Pollution of Cr and Zn were minimal compared to the other elements while concentrations of Cd and Hg were higher than their natural background values. Spatial variations of Cd, Hg, Pb and Cu in soil were illustrated; Pollution status and comparison in the four districts were also investigated. Higher concentrations of Hg and Cd were found in soils of Beichen than others indicating that Beichen was suffering from metal contamination. Principal Component Analysis in combination with local specific environment suggested that heavy metal contamination had different origination. Wastewater and sludge irrigation, air deposition might be the most important sources. These results, especially the spatial distribution of pollutants, would be helpful to develop proper management strategies and decrease source pollution by various remediation practices in Tianjin, China.

Assessment of 20 organochlorine pesticides (OCPs) pollution in suburban soil in Tianjin, China.

Soil contamination with organochlorine pesticides has aroused worldwide concerns considering their high toxicities and long-term persistence. In this study, 87 representative soil samples from suburban areas (Xiqing, Dongli, Jinnan, Beichen) of Tianjin, the third biggest city in China, were collected to evaluate the pollution of 20 organochlorine pesticides. Surface soil samples were air-dried and sieved. Ultrasonic extraction was used for organochlorine pesticides preparation prior to analysis with gas chromatography-mass spectrometry. It was revealed that p,p'-DDE, p,p'-DDD, o,p'-DDT, o,p'-DDD, hexachlorobenzene, dicofol and beta-HCH were seven pesticides detected most frequently. DDTs, HCHs and hexachlorobenzene were the predominant pesticide pollutants in soil. Spatial variation of these organochlorine pesticides in soil was illustrated; Pollution levels, characteristics and possible sources were also investigated. Most of other 13 kinds of pesticides were detected and the frequencies of detection were calculated to reveal the pollution status, which ranged from 0.0% (aldrin, dieldrin and endrin) to 34.5% (p,p'-DDT). These data were helpful to figure out the pollution of organochlorine pesticides and could be further used to evaluate the health risk associated with soil pollution.

Remediation mechanisms of mercapto-grafted palygorskite for cadmium pollutant in paddy soil.

The immobilization agent was the key factor that determined the success of remediation of heavy metal polluted soil. In this study, mercapto-grafted palygorskite (MP) as a novel and efficient immobilization agent was utilized for the remediation of Cd-polluted paddy soil in pot trials, and the remediation mechanisms were investigated in the aspect of soil chemistry and plant physiology with different rice cultivars as model plants. Mercapto-grafted palygorskite at applied doses of 0.1-0.3% could reduce Cd contents of brown rice and straws of different cultivars significantly. Both reduced DTPA-extractable Cd contents in rhizosphere and non-rhizosphere soil and decreasing Cd contents in iron plaques on rice root surfaces confirmed that MP was an efficient immobilization agent for Cd pollutant in paddy soil. In the aspect of soil chemistry, the pH values of rhizosphere and non-rhizosphere soils had no statistical changes in the MP treatment groups, but their zeta potentials decreased obviously, indicating that MP could enhance the fixation or sorption of Cd on soil compositions. In the aspect of antioxidant system, MP could increase POD activity of rice roots significantly to alleviate the stress of Cd to roots, and resulted in the decrease of T-AOC, SOD, and CAT activities of rice roots of the selected cultivars. MP had no inhabitation or enhancement effects on TSH of rice roots but enhance the contents of MTs and NPT to binding Cd to complete detoxification process. MP as a novel and efficient immobilization agent could complete the remediation effects through soil chemistry and plant physiological mechanisms.

Remediation mechanisms for Cd-contaminated soil using natural sepiolite at the field scale.

Remediation of heavy metal polluted agricultural soil is essential for human health and ecological safety and remediation mechanisms at the microscopic level are vital for their large-scale utilization. In this study, natural sepiolite was employed as an immobilization agent for in situ field-scale remediation of Cd-contaminated paddy soil and the remediation mechanisms were investigated in terms of soil chemistry and plant physiology. Natural sepiolite had a significant immobilization effect for bioavailable Cd contents in paddy soil, and consequently could lower the Cd concentrations of brown rice, husk, straw, and roots of rice plants by 54.7-73.7%, 44.0-62.5%, 26.5-67.2%, and 36.7-46.7%, respectively. Regarding soil chemistry, natural sepiolite increased the soil pH values and shifted the zeta potentials of soil particles to be more negative, enhancing the fixation or sorption of Cd on soil particles, and resulted in the reduction of HCl and DTPA extractable Cd concentrations in paddy soil. Natural sepiolite neither enhanced nor inhibited iron plaques on the rice root surface, but did change the chemical environments of Fe and S in rice root. Natural sepiolite improved the activities of antioxidant enzymes and enhanced the total antioxidant capacity to alleviate the stress of Cd. It also promotes the synthesis of GSH and NPT to complete the detoxification. In general, the remediation mechanisms of natural sepiolite for the Cd pollutant in paddy soil could be summarized as the collective effects of soil chemistry and plant physiology.