Designing Pt-based electrocatalysts with high surface energy

The reactivity of an electrocatalyst depends strongly on its surface structure. Pt-based electrocatalysts of nanocrystals (NCs) enclosed with high-index facets contain a large density of catalytically active sites formed from step and kink atoms on the facets and exhibit intrinsically superior activity. However, the Pt-based NCs of high-index facets do possess a high surface energy and are thermodynamically metastable, leading to a big challenge in their shape-controlled synthesis. To overcome the challenge, kinetic–thermodynamic control of crystal growth is indispensable and is currently realized mainly by electrochemical methods and surfactant-based wet chemical approaches. This Perspective reviews recent progresses in Pt-based electrocatalysts of monometallic and bimetallic NCs of high surface energy with different morphologies of convex or concave tetrahexahedron, trapezohedron, trisoctahedron, hexoctahedron, etc. Remarkable electrocatalytic performance of these NCs has been demonstrated. Despite the considerable progress already made, the electrocatalysts of NCs with high surface energy still hold significant future opportunities in both fundamental understanding and practical applications

Pd nanocrystals with continuously tunable high-index facets as a model nanocatalyst

Knowledge of the structure–reactivity relationship of catalysts is usually gained through using well-defined bulk single-crystal planes as model catalysts. However, there exists a huge gap between bulk single-crystal planes and practical nanocatalysts in terms of size, structural complexity, and local environment. Herein, we efficiently bridged this gap by developing a model nanocatalyst based on nanocrystals with continuously tunable surface structures. Pd nanocrystals with finely tunable facets, ranging from a flat {100} low-index facet to a series of {hk0} high-index facets, were prepared by an electrochemical square-wave potential method. The validity of the Pd model nanocatalyst has been demonstrated by structure–reactivity studies of electrocatalytic oxidation of small organic molecules. We further observed that Pd nanocrystals exhibited catalytic performance considerably different from bulk Pd single-crystal planes with the same Miller indices. Such differences were attributed to special catalytic functions conferred by nanocrystal edges. This study paves a promising route for investigating catalytic reactions effectively at the atomic level and nanoscales

Maximum Likelihood (ML) tree based on coding sequences of 53 protein-coding genes from 38 species, using <i>G</i>. <i>biloba</i> as outgroup.

<p>Numbers on each node are bootstrap support values.</p

The complete chloroplast genome sequence of <i>Epipremnum aureum</i> and its comparative analysis among eight Araceae species

<div><p><i>Epipremnum aureum</i> is an important foliage plant in the Araceae family. In this study, we have sequenced the complete chloroplast genome of <i>E</i>. <i>aureum</i> by using Illumina Hiseq sequencing platforms. This genome is a double-stranded circular DNA sequence of 164,831 bp that contains 35.8% GC. The two inverted repeats (IRa and IRb; 26,606 bp) are spaced by a small single-copy region (22,868 bp) and a large single-copy region (88,751 bp). The chloroplast genome has 131 (113 unique) functional genes, including 86 (79 unique) protein-coding genes, 37 (30 unique) tRNA genes, and eight (four unique) rRNA genes. Tandem repeats comprise the majority of the 43 long repetitive sequences. In addition, 111 simple sequence repeats are present, with mononucleotides being the most common type and di- and tetranucleotides being infrequent events. Positive selection pressure on <i>rps12</i> in the <i>E</i>. <i>aureum</i> chloroplast has been demonstrated via synonymous and nonsynonymous substitution rates and selection pressure sites analyses. <i>Ycf15</i> and <i>infA</i> are pseudogenes in this species. We constructed a Maximum Likelihood phylogenetic tree based on the complete chloroplast genomes of 38 species from 13 families. Those results strongly indicated that <i>E</i>. <i>aureum</i> is positioned as the sister of <i>Colocasia esculenta</i> within the Araceae family. This work may provide information for further study of the molecular phylogenetic relationships within Araceae, as well as molecular markers and breeding novel varieties by chloroplast genetic-transformation of <i>E</i>. <i>aureum</i> in particular.</p></div

Comparison of chloroplast sequences for <i>E</i>. <i>aureum</i> and other species within Araceae family.

<p>Comparison of chloroplast sequences for <i>E</i>. <i>aureum</i> and other species within Araceae family.</p

Gene distribution map for cp genome of <i>Epipremnum aureum</i>.

<p>Genes in inner and outer rings are transcribed in clockwise and counter-clockwise directions, respectively. Functional gene groups are indicated by different colors. For inner circles, dark grey and light grey represent GC and AT content, respectively.</p

Analysis of repeated sequences in <i>Epipremnum aureum</i> chloroplast genome.

<p>(A) Sorted by type of repeat. (B) Frequencies of repeat groups. (C) Numbers of each repeat type. (D) Sorted by size of repeat.</p

Comparison of nonsynonymous (dN) and synonymous (dS) substitution ratios among eight species of Araceae, using chloroplast genome of <i>Camellia crapnelliana</i> (Theaceae) as reference.

<p>Comparison of nonsynonymous (dN) and synonymous (dS) substitution ratios among eight species of Araceae, using chloroplast genome of <i>Camellia crapnelliana</i> (Theaceae) as reference.</p

Statistical analysis of SSRs in <i>Epipremnum aureum</i> chloroplast genome.

<p>(A) Sorted by type of SSR. (B) Frequency by type. (C) Sorted by region of genome.</p

Homogeneous {001}-BiOBr/Bi Heterojunctions: Facile Controllable Synthesis and Morphology-Dependent Photocatalytic Activity

The homogeneous BiOBr/Bi heterojunctions photocatalyst was synthesized from {001} facet dominated BiOBr flakes via a PVP-assisted in situ reduction reaction at room temperature. The high {001} facet exposure of BiOBr could induce the homogeneous distribution of metallic Bi on the surface of BiOBr. The introduction of PVP not only effectively protected the uniform structure but also largely promoted the photocatalysis properties. Compared to the bare BiOBr, an obviously enhanced photochemical performance was achieved over the homogeneous BiOBr/Bi pertaining to methyl orange (MO) degradation and photocurrent generation. The highly enhanced photocatalytic activity can be attributed not only to the surface plasmon resonance effect and efficient separation of electron–hole pairs by the metallic Bi but also to its uniform and regular structure. The present work provided a new approach to the development of attractive bismuth-based-photocatalysts/metallic Bi heterostructures with controllable structures and photocatalytic performance