A Highly Active Star Decahedron Cu Nanocatalyst for Hydrocarbon Production at Low Overpotentials

The electrochemical carbon dioxide reduction reaction (CO_2RR) presents a viable approach to recycle CO_2 gas into low carbon fuels. Thus, the development of highly active catalysts at low overpotential is desired for this reaction. Herein, a high‐yield synthesis of unique star decahedron Cu nanoparticles (SD‐Cu NPs) electrocatalysts, displaying twin boundaries (TBs) and multiple stacking faults, which lead to low overpotentials for methane (CH_4) and high efficiency for ethylene (C_2H_4) production, is reported. Particularly, SD‐Cu NPs show an onset potential for CH_4 production lower by 0.149 V than commercial Cu NPs. More impressively, SD‐Cu NPs demonstrate a faradaic efficiency of 52.43% ± 2.72% for C_2H_4 production at −0.993 ± 0.0129 V. The results demonstrate that the surface stacking faults and twin defects increase CO binding energy, leading to the enhanced CO_2RR performance on SD‐Cu NPs

2D perovskite stabilized phase-pure formamidinium perovskite solar cells.

Compositional engineering has been used to overcome difficulties in fabricating high-quality phase-pure formamidinium perovskite films together with its ambient instability. However, this comes alongside an undesirable increase in bandgap that sacrifices the device photocurrent. Here we report the fabrication of phase-pure formamidinium-lead tri-iodide perovskite films with excellent optoelectronic quality and stability. Incorporation of 1.67 mol% of 2D phenylethylammonium lead iodide into the precursor solution enables the formation of phase-pure formamidinium perovskite with an order of magnitude enhanced photoluminescence lifetime. The 2D perovskite spontaneously forms at grain boundaries to protect the formamidinium perovskite from moisture and suppress ion migration. A stabilized power conversion efficiency (PCE) of 20.64% (certified stabilized PCE of 19.77%) is achieved with a short-circuit current density exceeding 24 mA cm-2 and an open-circuit voltage of 1.130 V, corresponding to a loss-in-potential of 0.35 V, and significantly enhanced operational stability

Perovskite-polymer composite cross-linker approach for highly-stable and efficient perovskite solar cells.

Manipulation of grain boundaries in polycrystalline perovskite is an essential consideration for both the optoelectronic properties and environmental stability of solar cells as the solution-processing of perovskite films inevitably introduces many defects at grain boundaries. Though small molecule-based additives have proven to be effective defect passivating agents, their high volatility and diffusivity cannot render perovskite films robust enough against harsh environments. Here we suggest design rules for effective molecules by considering their molecular structure. From these, we introduce a strategy to form macromolecular intermediate phases using long chain polymers, which leads to the formation of a polymer-perovskite composite cross-linker. The cross-linker functions to bridge the perovskite grains, minimizing grain-to-grain electrical decoupling and yielding excellent environmental stability against moisture, light, and heat, which has not been attainable with small molecule defect passivating agents. Consequently, all photovoltaic parameters are significantly enhanced in the solar cells and the devices also show excellent stability

A Highly Active Star Decahedron Cu Nanocatalyst for Hydrocarbon Production at Low Overpotentials

The electrochemical carbon dioxide reduction reaction (CO_2RR) presents a viable approach to recycle CO_2 gas into low carbon fuels. Thus, the development of highly active catalysts at low overpotential is desired for this reaction. Herein, a high‐yield synthesis of unique star decahedron Cu nanoparticles (SD‐Cu NPs) electrocatalysts, displaying twin boundaries (TBs) and multiple stacking faults, which lead to low overpotentials for methane (CH_4) and high efficiency for ethylene (C_2H_4) production, is reported. Particularly, SD‐Cu NPs show an onset potential for CH_4 production lower by 0.149 V than commercial Cu NPs. More impressively, SD‐Cu NPs demonstrate a faradaic efficiency of 52.43% ± 2.72% for C_2H_4 production at −0.993 ± 0.0129 V. The results demonstrate that the surface stacking faults and twin defects increase CO binding energy, leading to the enhanced CO_2RR performance on SD‐Cu NPs

Presión arterial del recién nacido de madres preeclámpticas eclámpticas Hospital Regional de Cajamarca 2016

La presión arterial del recién nacido está sujeta a variaciones por diversas causas entre ellas la patología materna conocida como la preeclampsia El objetivo de la presente investigación fue determinar y analizar la presión arterial durante las primeras en las primeras 36 horas de vida, en forma periódica, de los recién nacidos hijos de madres preeclámpticas y la presión arterial de los recién nacidos hijos de madres no preeclámpticas, atendidos en el Hospital Regional de Cajamarca durante los meses de enero- febrero del año 2016. El estudio fue de tipo descriptivo, comparativo, correlacional, no experimental, de corte transversal y naturaleza prospectiva. Se incluyeron a 75 recién nacidos, hijos de madres preeclámpticas, y 75 recién nacidos de madres no preeclámpticas que cumplían con los criterios de inclusión y exclusión, atendidos en el Hospital Regional de Cajamarca durante los meses de enero y febrero del año 2016. Se realizaron mediciones de presión arterial en tres ocasiones: 12, 24 y 36 horas de nacimiento. Los resultados encontrados en la presente investigación fueron: edad materna promedio de 28.5 años, en gran porcentaje multíparas (49% y 48% en ambos grupos) y la mayoría con el diagnóstico de preeclampsia severa (52%). Los neonatos nacieron predominantemente por vía vaginal (56% y 86,8%), a término (76% y 94,7%), de sexo masculino con un porcentaje de 54,7% en el primer grupo y sexo femenino en el segundo grupo con 42%; con peso y talla al nacer promedio de 3026.7 gramos y 49.2 centímetros, respectivamente, con un puntaje de Apgar en su mayoría de 8 al minuto y 9 a los cinco minutos, con una cantidad mínima de neonatos con administración prenatales de corticoides (0,7%). Se determinó que la presión arterial se incrementó en las primeras 12 horas de vida en los recién nacidos de madres preeclámpticas, regularizándose, la mayoría, a las 36 horas, continuando elevada en un buen porcentaje (30,7%). En cuanto a los recién nacidos de madres no preeclámpticas una considerable cantidad tuvo presión arterial normal y los que tuvieron presión arterial alta en las primeras horas, se regularizaron a las 36 horasTesi

Highly active and stable stepped Cu surface for enhanced electrochemical CO₂ reduction to C₂H₄

Electrochemical CO₂ reduction to value-added chemical feedstocks is of considerable interest for renewable energy storage and renewable source generation while mitigating CO₂ emissions from human activity. Copper represents an effective catalyst in reducing CO₂ to hydrocarbons or oxygenates, but it is often plagued by a low product selectivity and limited long-term stability. Here we report that copper nanowires with rich surface steps exhibit a remarkably high Faradaic efficiency for C₂H₄ that can be maintained for over 200 hours. Computational studies reveal that these steps are thermodynamically favoured compared with Cu(100) surface under the operating conditions and the stepped surface favours C₂ products by suppressing the C₁ pathway and hydrogen production

Highly active and stable stepped Cu surface for enhanced electrochemical CO₂ reduction to C₂H₄

Electrochemical CO₂ reduction to value-added chemical feedstocks is of considerable interest for renewable energy storage and renewable source generation while mitigating CO₂ emissions from human activity. Copper represents an effective catalyst in reducing CO₂ to hydrocarbons or oxygenates, but it is often plagued by a low product selectivity and limited long-term stability. Here we report that copper nanowires with rich surface steps exhibit a remarkably high Faradaic efficiency for C₂H₄ that can be maintained for over 200 hours. Computational studies reveal that these steps are thermodynamically favoured compared with Cu(100) surface under the operating conditions and the stepped surface favours C₂ products by suppressing the C₁ pathway and hydrogen production

Compressed Intermetallic PdCu for Enhanced Electrocatalysis

Hydrogen evolution reaction (HER) is a key reaction in hydrogen production through water electrolysis. Platinum (Pt) is the best-known element for HER catalysis. Due to the scarcity of Pt, the development of non-Pt nanocatalysts is desired to achieve broad scale implementations. Here we demonstrate that the PdCu nanostructure containing an intermetallic B2 phase (PdCu-B2) shows a smaller Tafel slope, higher exchange current density, and lower overpotential for HER compared to commercial Pt/C in acidic conditions. Density functional theory (DFT) calculations demonstrate that the improved HER performance in acidic conditions can be attributed to the decrease in the hydrogen binding energy (HBE) on the compressed intermetallic PdCu-B2, shifting the HBE to a more optimal position even compared to Pt/C. In addition, PdCu-B2 exhibits the highest mass activity toward the formic acid oxidation reaction, making it a good anode catalyst candidate for formic-acid-based fuel cells

Highly Selective Electrochemical Reduction of CO2 into Methane on Nanotwinned Cu

The electrochemical carbon dioxide reduction reaction (CO2RR) is a promising route to close the carbon cycle by reducing CO2 into valuable fuels and chemicals. Electrocatalysts with high selectivity toward a single product are economically desirable yet challenging to achieve. Herein, we demonstrated a highly (111)-oriented Cu foil electrocatalyst with dense twin boundaries (TB) (tw-Cu) that showed a high Faradaic efficiency of 86.1 ± 5.3% toward CH4 at -1.2 ± 0.02 V vs the reversible hydrogen electrode. Theoretical studies suggested that tw-Cu can significantly lower the reduction barrier for the rate-determining hydrogenation of CO compared to planar Cu(111) under working conditions, which suppressed the competing C-C coupling, leading to the experimentally observed high CH4 selectivity

CO₂‑Promoted Electrocatalytic Reduction of Chlorinated Hydrocarbons

Electrochemical reactions and their catalysis are important for energy and environmental applications, such as carbon neutralization and water purification. However, the synergy in electrocatalysis between CO2 utilization and wastewater treatment has not been explored. In this study, we find that the electrochemical reduction of chlorinated organic compounds such as 1,2-dichloroethane, trichloroethylene, and tetrachloroethylene into ethylene in aqueous media, which is a category of challenging reactions due to the competition of H2 evolution, can be substantially enhanced by simultaneously carrying out the reduction of CO2 on an easily prepared and cost-effective Cu metal catalyst. In the case of 1,2-dichloroethane dechlorination, a 6-fold improvement in Faradaic efficiency and a 19-fold increase in partial current density are demonstrated. Through electrochemical kinetic studies, in situ Raman spectroscopy, and computational simulations, we further find that CO2 reduction reduces hydrogen coverage on the Cu catalyst, which not only exposes more active sites for the dechlorination reaction but also enhances the effective reductive potential on the catalyst surface and reduces the kinetic barrier of the rate-determining step