Yellow Luminescence of Polar and Nonpolar GaN Nanowires on <i>r</i>‑Plane Sapphire by Metal Organic Chemical Vapor Deposition

We have grown horizontal oriented, high growth rate, well-aligned polar (0001) single crystalline GaN nanowires and high-density and highly aligned GaN nonpolar (11–20) nanowires on <i>r</i>-plane substrates by metal organic chemical vapor deposition. It can be found that the polar nanowires showed a strong yellow luminescence (YL) intensity compared with the nonpolar nanowires. The different trends of the incorporation of carbon in the polar, nonpolar, and semipolar GaN associated with the atom bonding structure were discussed and proved by energy-dispersive X-ray spectroscopy, suggesting that C-involved defects are the origin responsible for the YL in GaN nanowires

Tuning Electronic Structures of Nonprecious Ternary Alloys Encapsulated in Graphene Layers for Optimizing Overall Water Splitting Activity

Electrochemical water splitting is considered as the most promising technology for hydrogen production. Considering overall water splitting for practical applications, catalysis of the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) should be performed in the same electrolyte, especially in alkaline solutions. However, designing and searching for highly active and inexpensive electrocatalysts for both OER and HER in basic media remain significant challenges. Herein, we report a facile and universal strategy for synthesizing nonprecious transition metals, binary alloys, and ternary alloys encapsulated in graphene layers by direct annealing of metal–organic frameworks. Density functional theory calculations prove that with an increase in the degree of freedom of alloys or a change in the metal proportions in FeCoNi ternary alloys, the electronic structures of materials can also be tuned intentionally by changing the number of transferred electrons between alloys and graphene. The optimal material alloys FeCo and FeCoNi exhibited remarkable catalytic performance for HER and OER in 1.0 M KOH, reaching a current density of 10 mA cm^–2 at low overpotentials of 149 mV for HER and 288 mV for OER. In addition, as an overall alkaline water electrolysis, they were comparable to that of the Pt/RuO₂ couple, along with long cycling stability

Rapid Adsorption Enables Interface Engineering of PdMnCo Alloy/Nitrogen-Doped Carbon as Highly Efficient Electrocatalysts for Hydrogen Evolution Reaction

The catalytic performance of Pd-based catalysts has long been hindered by surface contamination, particle agglomeration, and lack of rational structural design. Here we report a simple adsorption method for rapid synthesis (∼90 s) of structure-optimized Pd alloy supported on nitrogen-doped carbon without the use of surfactants or extra reducing agents. The material shows much lower overpotential than 30 wt % Pd/C and 40 wt % Pt/C catalysts while exhibiting excellent durability (80 h). Moreover, unveiled by the density functional theory (DFT) calculation results, the underlying reason for the outstanding performance is that the PdMnCo alloy/pyridinic nitrogen-doped carbon interfaces weaken the hydrogen-adsorption energy on the catalyst and thus optimize the Gibbs free energy of the intermediate state (Δ<i>G</i>_H*), leading to a remarkable electrocatalytic activity. This work also opens up an avenue for quick synthesis of a highly efficient structure-optimized Pd-based catalyst

Rapid Adsorption Enables Interface Engineering of PdMnCo Alloy/Nitrogen-Doped Carbon as Highly Efficient Electrocatalysts for Hydrogen Evolution Reaction

The catalytic performance of Pd-based catalysts has long been hindered by surface contamination, particle agglomeration, and lack of rational structural design. Here we report a simple adsorption method for rapid synthesis (∼90 s) of structure-optimized Pd alloy supported on nitrogen-doped carbon without the use of surfactants or extra reducing agents. The material shows much lower overpotential than 30 wt % Pd/C and 40 wt % Pt/C catalysts while exhibiting excellent durability (80 h). Moreover, unveiled by the density functional theory (DFT) calculation results, the underlying reason for the outstanding performance is that the PdMnCo alloy/pyridinic nitrogen-doped carbon interfaces weaken the hydrogen-adsorption energy on the catalyst and thus optimize the Gibbs free energy of the intermediate state (Δ<i>G</i>_H*), leading to a remarkable electrocatalytic activity. This work also opens up an avenue for quick synthesis of a highly efficient structure-optimized Pd-based catalyst

Vertical distribution of temperature, salinity, active silicate, POC, BSi, ²³⁴Th/²³⁸U ratios in the upper 100 m along Transect <i>I</i>.

<p>Vertical distribution of temperature, salinity, active silicate, POC, BSi, ²³⁴Th/²³⁸U ratios in the upper 100 m along Transect <i>I</i>.</p

²³⁴Th fluxes, POC/²³⁴Th and BSi/²³⁴Th ratios, and fluxes of POC and BSi out of the euphotic zone (100 m) in the tropical SCS.

<p>²³⁴Th fluxes, POC/²³⁴Th and BSi/²³⁴Th ratios, and fluxes of POC and BSi out of the euphotic zone (100 m) in the tropical SCS.</p

Distribution of temperature, salinity, active silicate, POC, BSi, and ²³⁴Th/²³⁸U ratios along Transect <i>III</i>.

<p>Distribution of temperature, salinity, active silicate, POC, BSi, and ²³⁴Th/²³⁸U ratios along Transect <i>III</i>.</p

Sampling stations along Transects <i>I</i>, <i>II</i>, and <i>III</i> in the tropical SCS, and the sea-level anomaly (SLA) on 10 November (left) and 17 November (right), 2010.

<p>The color scale units are centimeters.</p

Comparison of some parameters between the eddy and ordinary stations.

<p>^a The values in parentheses stand for the number of samples.</p><p>^b E and O refer to the eddy and ordinary stations. The <i>p</i> values were obtained from <i>t</i>-tests assuming <i>α</i> = 0.05.</p><p>E/O is the ratio of a specific parameter in the eddy to the surrounding water. The errors represent the standard deviation for data used to calculate the means.</p

Temperature, salinity, activity concentrations of ²³⁴Th and ²³⁸U, POC and BSi concentrations, and the δ¹³C value of POC in the SCS in November, 2010.

<p>The errors of the ²³⁴Th datasets represent the propagated errors from the statistical count errors of ²³⁴Th based on two measurements.</p