Enhanced Activity for Hydrogen Evolution Reaction over CoFe Catalysts by Alloying with Small Amount of Pt

The hydrogen evolution reaction highly relied on Pt electrocatalysts, with high activity and stability. In the past few years, a host of efforts have been made in the development of novel platinum nanostructures with a low amount of Pt because the scarcity and high price of Pt hinder its practical applications. Here, we report the preparation of PtCo­Fe@CN electrocatalysts with a remarkably reduced Pt loading amount of 4.60% by annealing Pt-doped metal–organic frameworks (MOFs). The electrocatalyst demonstrated an outstanding performance with only 45 mV overpotential to achieve the 10 mA cm^–2 current density, which is quite close to that of the commercial 20% Pt/C catalyst. The enhanced catalytic capability is originated from the modification of the electronic structures of CoFe by alloying with Pt. The results indicate that robust and superstable alloy electrocatalysts which contain a very small amount of noble metal could be prepared by annealing noble metal-doped MOFs

Estimated proportion of diet for <i>P. japonica</i> adults originating from C₃-based resources and/or C₄-based resources in the field from 2008–2010.^a

a<p>Proportions of diet for <i>P. japonica</i> adults were estimated based on the carbon isotope ratio linear equation and δ¹³C value of <i>P. japonica</i> adults collected in field.</p

Carbon isotope ratios (mean δ¹³±SD) of <i>P. japonica</i> adults collected from maize patches.

<p>In 2008 (<b>A</b>), 2009 (<b>B</b>), 2010 (<b>C</b>). MV, middle δ¹³C values of <i>P. japonica</i> adults was −16.71 as the proportion of aphids from a C₃-based resource (cotton aphids reared on cotton) and a C₄ -based resource (maize aphids reared on maize) was 50%.</p

Carbon isotope ratios of <i>P. japonica</i> adults in laboratory.

<p>(<b>A</b>) Carbon isotope ratios of plant and insect species used in dietary switching experiment. Carbon isotope ratios (mean δ¹³±SD) of plants (cotton and maize), aphids from cotton and maize, and <i>P. japonica</i> adults. Adult (C3) was raised on cotton aphids. Adult (C4) was raised on maize aphids. MV, middle δ¹³C values of <i>P. japonica</i> adults was −16.71‰ as the proportion of aphids from a C₃-based resource and a C₄ -based resource was 50%. Error bars indicate the SD. (<b>B</b>) Carbon isotope ratios of <i>P. japonica</i> adults in dietary switching experiment. Carbon isotope ratios (mean δ¹³±SD) of laboratory-reared <i>P. japonica</i> adults (▴) before and after a shift in diet from a C₃-based resource (cotton aphids reared on cotton) to one based on C₄ plants (maize aphids reared on maize). (<b>C</b>) Relationship of δ¹³C values of <i>P. japonica</i> and proportions of aphids form C₃ and C₄-based resource. Aphids were from a C₃-based resource and a C₄ -based resource on which they were grown in the laboratory. The ladybird beetles were grown from eggs to adults on five food mixtures consisting of, respectively, 100% cotton aphids/0% maize aphids, 75% cotton aphids/25% maize aphids, 50% cotton aphids/50% maize aphids, 25% cotton aphids/75% maize aphids and 0% cotton aphids/100% maize aphids. Linear equation Y = 0.120X-22.723 (<i>F</i> = 57.08, <i>P</i> = 0.005, <i>R</i>² = 0.95): where Y is δ¹³ values of <i>P. japonica</i>, X is proportion of aphids from a C₃-based resource and a C₄-based resource.</p

Dynamics of <i>P. japonica</i> adults.

<p>Densities of <i>P. japonica</i> adults in cotton patches (black triangle) and maize patches (red circle) in field landscape plots in 2008 (<b>A</b>), 2009 (<b>B</b>), and 2010 (<b>C</b>). *Significant differences between densities of <i>P. japonica</i> adults in cotton patches and maize patches at p<0.05. **Significant differences between densities of <i>P. japonica</i> adults in cotton patches and maize patches at p<0.01. Densities of accumulative <i>P. japonica</i> adults in cotton patches and maize patches at all sample dates of field landscape plots in 2008 (<b>D</b>), 2009 (<b>E</b>) or 2010 (<b>F</b>). Different lowercases above the bars indicate significant differences in densities of accumulative <i>P. japonica</i> adults in cotton patches and maize patches at p<0.05. Data are presented as adults per square meter of crop plants (mean±SE) with separate field landscape plots used as replicates. Sample size of cotton patch and maize patch are both 20. N indicates the size of samples tested.</p

Dynamics of aphid density.

<p>Aphid density in cotton patches (black triangle) and maize patches (red circle) in field landscape plots in 2008 (<b>A</b>), 2009 (<b>B</b>), and 2010 (<b>C</b>). The data for aphid density were log-transformed (ln(n+1)). *Significant differences between densities of aphid in cotton patches and maize patches at p<0.05. **Significant differences between densities of aphid in cotton patches and maize patches at p<0.01. Densities of accumulative aphid in cotton patches and maize patches at all sample dates of field landscape plots in 2008 (<b>D</b>), 2009 (<b>E</b>) or 2010 (<b>F</b>). Different lowercases above the bars indicate significant differences in densities of accumulative aphid in cotton patches and maize patches at p<0.05. Data are presented per square meter of crop plants (mean±SE) with separate field landscape plots used as replicates. Sample size of cotton patch and maize patch are both 20. N indicates the size of samples tested.</p

Controllable Carrier Type in Boron Phosphide Nanowires Toward Homostructural Optoelectronic Devices

The p–n junction is one important and fundamental building block of the optoelectronic age. However, electrons and holes will be severely scattered in heterostructures led by the grain boundary at the alloy interface between two dissimilar semiconductors. In this work, we present boron phosphide (BP) nanowires with artificially controllable carrier type for the fabrication of homojunctions via adjusting borane/phosphine ratio during the deposition process, both prove high crystallization with fewer impurities. The homojunctions that consist of  n-type and p-type BP nanowires show apparent photovoltaic effect [external quantum efficiency ≈ 10% under a ∼0.4 pW light @ 600 nm] and the quenched photoluminescence within the junction area, which indicates the effective separation and transfer of photogenerated charge carriers at the interface. The achievement of controllable carrier type implemented in the same material ushers in a frontier for the design of nanoscale homojunctions toward advanced optoelectronic devices

Relationship between <i>P. japonica</i> eggs, larva and adults and and aphids in landscape plots during 2008, 2009 and 2010.^a

a<p>x is the aphid density data, which was log-transformed (ln(n+1)) for analysis. y is density of <i>P. japonica</i> eggs, larva and adults.</p

Linear regression between densities of <i>P. japonica</i> adults on maize and landscape shape index of plot.^a

a<p>x is the landscape shape index of plot, y is the densities of <i>P. japonica</i> adults on maize patches of plot.</p>b<p>the densities of <i>P. japonica</i> adults on maize patches in each plot were accumulated in all sample dates in 2008, 2009 or 2010.</p

Spatial layout of the field experiment.

<p>The field was 90 m×90 m and divided into 25 15 m×15 m plots, each plot consisting of 24 rows and 50 columns. The spacing between neighboring plots was 3–4 m. Green and red areas in plot indicate the planting of cotton and maize.</p