Phase Engineering of Intermetallic PtBi2 Nanoplates for Formic Acid Electrochemical Oxidation.

Phase engineering of Pt-based intermetallic catalysts has been demonstrated as a promising strategy to optimize catalytic properties for a direct formic acid fuel cell. Pt-Bi intermetallic catalysts are attracting increasing interest due to their high catalytic activity, especially for inhibiting CO poisoning. However, the phase transformation and synthesis of intermetallic compounds usually occurring at high temperatures leads to a lack of control of the size and composition. Here, we report the synthesis of intermetallic ß-PtBi2 and γ-PtBi2 two-dimensional nanoplates with controlled sizes and compositions under mild conditions. The different phases of intermetallic PtBi2 can significantly affect the catalytic performance of the formic acid oxidation reaction (FAOR). The obtained ß-PtBi2 nanoplates exhibit an excellent mass activity of 1.1 ± 0.01 A mgPt-1 for the FAOR, which is 30-fold higher than that of commercial Pt/C catalysts. Moreover, intermetallic PtBi2 demonstrates high tolerance to CO poisoning, as confirmed by in situ infrared absorption spectroscopy.

Functionalized Titanium-Based MOF for Cr(VI) Removal from Wastewater.

The removal of toxic Cr(VI) is a hot topic in the environmental remediation field. In this work, a Ti-based metal-organic framework (MOF) (MIL-125(Ti)-NH2) was successfully functionalized by introducing amidoxime groups for the first time. The functionalized material (MIL-125(Ti)-AO) exhibited excellent Cr(VI) adsorption performance with a maximum adsorption capacity of 271 mg·g-1 according to Langmuir fitting. More importantly, during the adsorption process, Cr(VI) could be simultaneously reduced to less toxic Cr(III) species, and the residual concentration of chromium in the treated water was below the drinking water limit (0.05 mg·L-1) recommended by WHO. The effects of initial pH, contact time, and the initial concentration of Cr(VI) and the presence of competitive ions on the Cr(VI) adsorption performance of MIL-125(Ti)-AO were systematically investigated. The excellent Cr(VI) removal performance of MIL-125(Ti)-AO was attributed to the synergistic effects of simultaneous adsorption of Cr(VI) and Cr(III) by a [Ti-O] bond when Cr(VI) was reduced to Cr(III) by amidoxime groups.

V2 O3 /MnS Arrays as Bifunctional Air Electrode for Long-Lasting and Flexible Rechargeable Zn-Air Batteries.

Exploring highly efficient, stable, and cost-effective bifunctional electrocatalysts is crucial for the wide commercialization of rechargeable Zn-air batteries. Herein, a vanadium-oxide-based hybrid air electrode comprising a heterostructure of V2 O3 and MnS (V2 O3 /MnS) is reported. The V2 O3 /MnS catalyst shows a decent catalytic activity that is comparable to Pt/C toward the oxygen reduction reaction and acceptable toward oxygen evolution. The extraordinary stability as well as the low cost set the V2 O3 /MnS among the best bifunctional oxygen electrocatalysts. In a demonstration of an assembled liquid-state Zn-air battery using V2 O3 /MnS as cathode, high power density (118 mW cm-2 ), specific capacity (808 mAh gZn -1 ), and energy density (970 Wh kgZn -1 ), as well as the outstanding rechargeability and durability for 4000 cycles (>1333 h, i.e., >55 days) are enabled. The V2 O3 /MnS is also integrated into an all-solid-state Zn-air battery to demonstrate its great potential as a flexible power source for next-generation electronics. Density functional theory calculations further elucidate the origin of the intrinsic activity and stability of the V2 O3 /MnS heterostructure.

SnO2 Quantum Dots Enabled Site-Directed Sodium Deposition for Stable Sodium Metal Batteries.

Dendrite growth has been severely impeding the implementation of sodium (Na) metal batteries, which is regarded as one of the most promising candidates for next-generation high-energy batteries. Herein, SnO2 quantum dots (QDs) are homogeneously dispersed and fully covered on a 3D carbon cloth scaffold (SnO2-CC) with high affinity to molten Na, given that SnO2 spontaneously initiates alloying reactions with Na and provides low nucleation barrier for Na deposition. Molten Na can be rapidly infused into the SnO2-CC scaffold as a free-standing anode material. Because of the affinity between SnO2 and Na ion, SnO2 QDs can effectively guide Na nucleation and attains site-directed dendrite-free Na deposition when combined with the 3D CC scaffold. This electrochemically stable anode enables almost 400 cycles at ultrahigh current density of 20 mA cm-2 in Na symmetric battery and delivers superior cycling performance and reversible rate capability in Na-Na3V2(PO4)3 full batteries.

Two-Dimensional Pd Rafts Confined in Copper Nanosheets for Selective Semihydrogenation of Acetylene.

The development of highly selective and active catalysts to catalyze an industrially important semihydrogenation reaction remains an open challenge. Here, we report the design of a bimetallic Pd/Cu(111) catalyst with Pd rafts confined in a Cu nanosheet, which exhibits desirable catalytic performance for acetylene semihydrogenation to ethylene with the selectivity of >90%. Theory calculations show that Pd atoms replacing neighboring Cu atoms in Cu(111) can improve the catalytic activity by reducing the energy barrier of the semihydrogenation reaction, as compared to unsubstituted Cu(111), and can improve the selectivity by weakening the adsorption of C2H4, as compared to a Pd(111) surface. The presence of Pd rafts confined in Cu nanosheets effectively turns on Cu nanosheets for semihydrogenation of acetylene with high activity and selectivity under mild reaction conditions. This work offers a well-defined nanostructured Pd/Cu(111) model catalyst that bridges the pressure and materials' gap between surface-science catalysis and practical catalysis.

Thermodynamic Regulation of Dendrite-Free Li Plating on Li3Bi for Stable Lithium Metal Batteries.

Rechargeable batteries with metallic lithium (Li) anodes are attracting ever-increasing interests because of their high theoretical specific capacity and energy density. However, the dendrite growth of the Li anode during cycling leads to poor stability and severe safety issues. Here, Li3Bi alloy coated carbon cloth is rationally chosen as the substrate of the Li anode to suppress the dendrite growth from a thermodynamic aspect. The adsorption energy of a Li atom on Li3Bi is larger than the cohesive energy of bulk Li, enabling uniform Li nucleation and deposition, while the high diffusion barrier of the Li atom on Li3Bi blocks the migration of adatoms from adsorption sites to the regions of fast growth, which further ensures uniform Li deposition. With the dendrite-free Li deposition, the composite Li/Li3Bi anode enables over 250 cycles at an ultrahigh current density of 20 mA cm-2 in a symmetrical cell and delivers superior electrochemical performance in full batteries.

Health risk assessment of As due to rice ingestion based on iAs distribution and actual consumption patterns for the residents in Beijing: a cross-sectional study.

As a well-known human carcinogen, arsenic (As) could pose various detrimental health effects to humans mainly through the exposure pathway of food ingestion. In comparison with other foods, rice can accumulate more arsenic due to its tissue specificity. Thus, it is of great significance to assess the health risk of As due to rice ingestion. However, the study on risk assessment from exposure to As in rice is still in an early stage and lack accuracy to date. In this study, after obtaining the rice exposure behavior patterns based on a questionnaire survey, a total of 160 rice samples, which consisted of 4 types (i.e., japonica, indica, glutinous and brown rice), rice from 4 areas and consumed by most of the population in Beijing, were collected. On the basis of the actual intake rate and the species weighted average concentration of consumed rice, average daily exposure dose and health risks of inorganic As (iAs) from rice ingestion were assessed for the population among different genders and ages in Beijing. The results show that japonica rice and rice from Northeast China had higher As content, with the same value of 0.064 mg kg-1. And, they were the most popular rice consumed by people, with the intake rates of 75.50 g d-1, and 67.91 g d-1, respectively. The proportion of iAs to total As (tAs) was 58.34%, with a range of 43.18-71.88%. The average daily dose of iAs for the population was 1.15 × 10-4, which mainly came from japonica rice and the rice from Northeast China ingestion. In comparison with the acceptable non-cancer risk, which had a HQ value of 0.38, the carcinogenic risk of the population in Beijing was 1.73 × 10-4 on average. Furthermore, males had higher carcinogenic risk (1.88 × 10-4) than females (1.62 × 10-4), and the people in the age of 45-55 suffered from the highest carcinogenic risk (2.22 × 10-4), which mainly was attributed to the japonica rice and the rice from Northeast China. This study strengthened that appropriate dietary patterns should be paid more attention in order to control the health risk due to As exposure.

Author Correction: Eliminating dissolution of platinum-based electrocatalysts at the atomic scale.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Eliminating dissolution of platinum-based electrocatalysts at the atomic scale.

A remaining challenge for the deployment of proton-exchange membrane fuel cells is the limited durability of platinum (Pt) nanoscale materials that operate at high voltages during the cathodic oxygen reduction reaction. In this work, atomic-scale insight into well-defined single-crystalline, thin-film and nanoscale surfaces exposed Pt dissolution trends that governed the design and synthesis of durable materials. A newly defined metric, intrinsic dissolution, is essential to understanding the correlation between the measured Pt loss, surface structure, size and ratio of Pt nanoparticles in a carbon (C) support. It was found that the utilization of a gold (Au) underlayer promotes ordering of Pt surface atoms towards a (111) structure, whereas Au on the surface selectively protects low-coordinated Pt sites. This mitigation strategy was applied towards 3 nm Pt3Au/C nanoparticles and resulted in the elimination of Pt dissolution in the liquid electrolyte, which included a 30-fold durability improvement versus 3 nm Pt/C over an extended potential range up to 1.2 V.

Catalyst design by scanning probe block copolymer lithography.

Scanning probe block copolymer lithography (SPBCL), in combination with density-functional theory (DFT), has been used to design and synthesize hydrogen evolution catalysts. DFT was used to calculate the hydrogen adsorption energy on a series of single-element, bimetallic, and trimetallic (Au, Pt, Ni, and Cu) substrates to provide leads that could be synthesized in the form of alloy or phase-separated particles via SPBCL. PtAuCu (18 nm, ∼1:1:1 stoichiometry) has been identified as a homogeneous alloy phase that behaves as an effective hydrogen evolution catalyst in acidic aqueous media, even when it is made in bulk form via solution phase methods. Significantly, the bulk-prepared PtAuCu/C nanocatalyst discovered via this process exhibits an activity seven times higher than that of the state-of-the-art commercial Pt/C catalyst (based upon Pt content). The advantage of using SPBCL in the discovery process is that one can uniformly make particles, each consisting of a uniform phase combination (e.g., all alloy or all phase-segregated species) at a fixed elemental ratio, an important consideration when working with polyelemental species where multiple phases may exist.

Promoting Formation of Oxygen Vacancies in Two-Dimensional Cobalt-Doped Ceria Nanosheets for Efficient Hydrogen Evolution.

As an alternative for depleting fossil fuel energy, hydrogen economy desires low-cost and efficient hydrogen production from water splitting. In order to explore a cheap, abundant, active, and durable catalyst for the electrocatalytic hydrogen evolution reaction (HER), two-dimensional (2D) ceria nanosheets are produced through a thermal decomposition exfoliation method from CeCO3OH with a layer-stacked structure. The additional cobalt dopant promotes formation of oxygen vacancies in ceria nanosheets and, in turn, optimizes hydrogen binding/water dissociation and increases the active sites. As a result, the 2D Co-doped CeO2 nanosheets exhibit an excellent catalytic performance in alkaline HER such that the overpotential is as low as 132 and 215 mV to deliver a high current density of 100 and 500 mA cm-2, respectively, outperforming Pt. Such 2D Co-doped CeO2 nanosheets are also durable HER electrocatalysts, as the activity loss during an extended period of operation is nearly negligible.

Health risks and source identification of dietary exposure to indicator polychlorinated biphenyls (PCBs) in Lanzhou, China.

Polychlorinated biphenyls (PCBs) are widely present in multiple environmental media even long after the phaseout, posing a health risk to the general population. Dietary intake is the major exposure route of PCBs; however, information is limited regarding PCBs in food that people directly consume. This study aims to measure personal exposure to indicator PCBs, evaluate the health risks, and identify their sources in a typical metropolitan city in China. Multi-day food samples were collected from 21 subjects in Lanzhou, Gansu Province, in two seasons using the duplicate plate method. Samples were extracted and analyzed for seven indicator PCBs using gas chromatography/mass spectrometry. Average daily doses (ADDs) of ∑7PCBs were estimated using Monte Carlo analysis with food intake information. Results show that PCB-118 and PCB-180 were the major congeners in food samples with average concentrations of 1.42 and 1.11 ng/g, respectively. The average (± SD) ADD of ∑7PCBs was 26.47 ± 22.10 ng/kg day among adults aged 18-69 years and displayed small variation across age groups. Comparing with the chronic RfD of 7 ng/kg day, 67% of people had their ADDs exceeding this threshold. The median cancer risk was 5.52 × 10-5, and 51% of residents had risks exceeding the action level of 10-4. The principal component analysis identified waste incineration, gasoline engine production, and leakage of #1 PCBs as the major PCBs sources. In conclusion, a large portion of Lanzhou residents has high non-cancer and cancer risks from dietary exposure to PCBs, which warrants control actions targeting these major sources.

Advances in the Interfacial Assembly of Mesoporous Silica on Magnetite Particles.

Interfacing magnetic particles with ordered mesoporous materials is an effective direction for the development of functional porous composite materials with rationally designed core-shell structures. Owing to the combined properties of magnetic nanoparticles and mesoporous silica (high surface area, large pore volume, porosity, and biocompatibility), core-shell magnetic mesoporous silica materials have generated tremendous interest in various disciplines, including chemistry, materials, bioengineering, and biomedicine. Interfacial assembly strategies enable the rational construction of magnetic mesoporous silica materials with well-defined core-shell structure, morphology, pore parameters, and surface wettability, which can decisively influence their physical and chemical properties and thus improve their application performance. This Minireview summarizes recent progress in the synthesis of core-shell magnetic mesoporous silica and the adjustment of key parameters, including pore size, morphology, and pore orientation.

Ag-Sn Bimetallic Catalyst with a Core-Shell Structure for CO2 Reduction.

Converting greenhouse gas carbon dioxide (CO2) to value-added chemicals is an appealing approach to tackle CO2 emission challenges. The chemical transformation of CO2 requires suitable catalysts that can lower the activation energy barrier, thus minimizing the energy penalty associated with the CO2 reduction reaction. First-row transition metals are potential candidates as catalysts for electrochemical CO2 reduction; however, their high oxygen affinity makes them easy to be oxidized, which could, in turn, strongly affect the catalytic properties of metal-based catalysts. In this work, we propose a strategy to synthesize Ag-Sn electrocatalysts with a core-shell nanostructure that contains a bimetallic core responsible for high electronic conductivity and an ultrathin partially oxidized shell for catalytic CO2 conversion. This concept was demonstrated by a series of Ag-Sn bimetallic electrocatalysts. At an optimal SnOx shell thickness of ∼1.7 nm, the catalyst exhibited a high formate Faradaic efficiency of ∼80% and a formate partial current density of ∼16 mA cm-2 at -0.8 V vs RHE, a remarkable performance in comparison to state-of-the-art formate-selective CO2 reduction catalysts. Density-functional theory calculations showed that oxygen vacancies on the SnO (101) surface are stable at highly negative potentials and crucial for CO2 activation. In addition, the adsorption energy of CO2- at these oxygen-vacant sites can be used as the descriptor for catalytic performance because of its linear correlation to OCHO* and COOH*, two critical intermediates for the HCOOH and CO formation pathways, respectively. The volcano-like relationship between catalytic activity toward formate as a function of the bulk Sn concentration arises from the competing effects of favorable stabilization of OCHO* by lattice expansion and the electron conductivity loss due to the increased thickness of the SnOx layer.

Atomic Structure of Pt3Ni Nanoframe Electrocatalysts by in Situ X-ray Absorption Spectroscopy.

Understanding the atomic structure of a catalyst is crucial to exposing the source of its performance characteristics. It is highly unlikely that a catalyst remains the same under reaction conditions when compared to as-synthesized. Hence, the ideal experiment to study the catalyst structure should be performed in situ. Here, we use X-ray absorption spectroscopy (XAS) as an in situ technique to study Pt3Ni nanoframe particles which have been proven to be an excellent electrocatalyst for the oxygen reduction reaction (ORR). The surface characteristics of the nanoframes were probed through electrochemical hydrogen underpotential deposition and carbon monoxide electrooxidation, which showed that nanoframe surfaces with different structure exhibit varying levels of binding strength to adsorbate molecules. It is well-known that Pt-skin formation on Pt-Ni catalysts will enhance ORR activity by weakening the binding energy between the surface and adsorbates. Ex situ and in situ XAS results reveal that nanoframes which bind adsorbates more strongly have a rougher Pt surface caused by insufficient segregation of Pt to the surface and consequent Ni dissolution. In contrast, nanoframes which exhibit extremely high ORR activity simultaneously demonstrate more significant segregation of Pt over Ni-rich subsurface layers, allowing better formation of the critical Pt-skin. This work demonstrates that the high ORR activity of the Pt3Ni hollow nanoframes depends on successful formation of the Pt-skin surface structure.

Experience of advance directives in a hospice center.

To protect patient autonomy when confronting death, the importance of advance directives (ADs) has recently became an issue and gradually accepted in Korea. However, in real practice, ADs were not completed by patients but their families in most cases. To analyze the current situation of performing ADs, we reviewed medical charts of 214 terminal cancer patients admitted to the hospice center from October 2012 to September 2013. Seventy-six (35.5%) patients completed ADs. All ADs were completed by patients themselves. The most common reason for not completing ADs was poor physical and/or mental condition. As a proxy, the majority of patients preferred their spouses (55.3%). Few patients wanted life sustaining treatment (1.3%), however palliative sedation was accepted in 89.5%. The median timing of ADs after admission was three (0-90) days, and duration of survival since ADs was 22 (1-340) days. In conclusion, approximately one third of terminal cancer patients completed ADs by themselves. Considering that patient's poor condition is the main reason for not completing ADs, earlier discussion regarding ADs is necessary to enhance patients' participation.

Multimetallic core/interlayer/shell nanostructures as advanced electrocatalysts.

The fine balance between activity and durability is crucial for the development of high performance electrocatalysts. The importance of atomic structure and compositional gradients is a guiding principle in exploiting the knowledge from well-defined materials in the design of novel class of core-shell electrocatalysts comprising Ni core, Au interlayer, and PtNi shell (Ni@Au@PtNi). This multimetallic system is found to have the optimal balance of activity and durability due to the synergy between the stabilizing effect of subsurface Au and modified electronic structure of surface Pt through interaction with subsurface Ni atoms. The electrocatalysts with Ni@Au@PtNi core-interlayer-shell structure exhibit high intrinsic and mass activities as well as superior durability for the oxygen reduction reaction with less than 10% activity loss after 10,000 potential cycles between 0.6 and 1.1 V vs the reversible hydrogen electrode.

Using surface segregation to design stable Ru-Ir oxides for the oxygen evolution reaction in acidic environments.

The methods used to improve catalytic activity are well-established, however elucidating the factors that simultaneously control activity and stability is still lacking, especially for oxygen evolution reaction (OER) catalysts. Here, by studying fundamental links between the activity and stability of well-characterized monometallic and bimetallic oxides, we found that there is generally an inverse relationship between activity and stability. To overcome this limitation, we developed a new synthesis strategy that is based on tuning the near-surface composition of Ru and Ir elements by surface segregation, thereby resulting in the formation of a nanosegregated domain that balances the stability and activity of surface atoms. We demonstrate that a Ru0.5Ir0.5 alloy synthesized by using this method exhibits four-times higher stability than the best Ru-Ir oxygen evolution reaction materials, while still preserving the same activity.

Effect of the defoliant tribufos on the reproductive ability of Japanese quail (Coturnix japonica).

As a cotton defoliator, tribufos (S,S,S-tributyl phosphorotrithioate) is widespread in the environment. It can cause neurotoxicity in chickens, reproductive toxicity in rats, and can also cause headaches and nausea in humans. However, little is known about its impact on the reproduction of birds. Here, by analyzing the differences in reproductive indexs and histopathological characteristics, we investigated the chronic effects of 32 mg a.i./kg, 160 mg a.i./kg and 800 mg a.i./kg tribufos treatment on the reproductive ability of Japanese quail (Coturnix japonica). The results indicated that 32 mg a.i./kg and 160 mg a.i./kg tribufos treatment significantly reduced the food intake of quails, significantly increased the broken egg rate, and had adverse effects on gonads and liver tissue. The 160 mg a.i./kg tribufos treatment also significantly reduced the average egg production. Moreover, 800 mg a.i./kg treatment had significant negative effects on feed intake (FI), body weight (BW), eggshell thickness, egg production (EP), fertilization rate, hatchability and progeny 14-d survival rate, and it also significantly increased the broken egg rate. In addition, tribufos exposure caused lesions in quail gonads and liver tissue. Overall, our results revealed that tribufos had adverse effects on the reproductive ability of Japanese quail, especially at high concentrations.

Design of Pt-Pd binary superlattices exploiting shape effects and synergistic effects for oxygen reduction reactions.

Large-area icosahedral-AB(13)-type Pt-Pd binary superlattices (BNSLs) are fabricated through self-assembly of 6 nm Pd nanocrystals (NCs) and 13 nm Pt octahedra at a liquid-air interface. The Pt-Pd BNSLs enable a high activity toward electrocatalysis of oxygen reduction reaction (ORR) by successfully exploiting the shape effects of Pt NCs and synergistic effects of Pt-Pd into a single crystalline nanostructure. The Pt-Pd BNSLs are promising catalysts for the oxygen electrode of fuel cells.