1,720,967 research outputs found
Boosting Electrocatalytic HER Activity of 3D Interconnected CoSP via Metal Doping: Active and Stable Electrocatalysts for pH-Universal Hydrogen Generation
No full text© 2020 American Chemical Society. All rights reserved.Recently, many research studies have been focused on anion or cation substitution into the lattice of pyrite-type cobalt disulfide (CoS2) for enhancing the hydrogen evolution reaction (HER) performance. Nonetheless, finding the correct pair of anion-cation dual substitution with added synergistic effect for boosting pH-universal HER activity remains an ongoing challenge. Additionally, a generalized activity descriptor and the HER mechanism in alkaline media remain elusive. Herein, to elucidate the HER mechanism and obtain the suitable anion-cation pair, we investigated the codoping of metal cations (Ti/V/Cr/Mn/Fe) and phosphorus anions into the CoS2 moiety. Our theoretical prediction revealed that Ti and P codoping into CoS2 exhibits superior HER performance at both pH 0 and 14, which is ascribed to the weak hydrogen binding energy in acid and fast water dissociation kinetics in alkaline media, thereby promoting HER. Remarkably, a follow-up experiment confirmed that Ti-CoSP showed astonishing HER activity inducing low overpotentials of 44 and 132 mV at -10 mA cm-2 in acidic and alkaline media, respectively, with superior stability for 40 h11Nsciescopu
Phase-selective active sites on ordered/disordered titanium dioxide enable exceptional photocatalytic ammonia synthesis
No full text© The Royal Society of Chemistry 2021. Photocatalytic N-2 fixation to NH3 via defect creation on TiO2 to activate ultra-stable N N has drawn enormous scientific attention, but poor selectivity and low yield rate are the major bottlenecks. Additionally, whether N-2 preferentially adsorbs on phase-selective defect sites on TiO2 in correlation with appropriate band alignment has yet to be explored. Herein, theoretical predictions reveal that the defect sites on disordered anatase (A(d)) preferentially exhibit higher N-2 adsorption ability with a reduced energy barrier for a potential-determining-step (*N-2 to NNH*) than the disordered rutile (R-d) phase of TiO2. Motivated by theoretical simulations, we synthesize a phase-selective disordered-anatase/orderedrutile TiO2 photocatalyst (Na-A(d)/R-o)by sodium-amine treatment of P25-TiO2 under ambient conditions, which exhibits an efficient NH3 formation rate of 432 mu mol g(-1) h(-1), which is superior to that of any other defect-rich disordered TiO2 under solar illumination with a high apparent quantum efficiency of 13.6% at 340 nm. The multi-synergistic effects including selective N-2 chemisorption on the defect sites of Na-A(d) with enhanced visible-light absorption, suitable band alignment, and rapid interfacial charge separation with R-o enable substantially enhanced N-2 fixation.11Nsciescopu
Electron deficient boron-doped amorphous carbon nitride to uphill N2 photo-fixation through π back donation
No full text© 2022 Elsevier B.V.The photocatalytic Nitrogen fixation to NH3 by using water as a protonation source is a requisite renovation for life. Albeit, the activation and adsorption of robust N[tbnd]N is the bottleneck in NH3 synthesis. Here, we report an amorphous-wrinkled hollow-tubular electron-deficient boron-doped carbon nitride (BCN) for improved photocatalytic N2 fixation via “σ donation and π back donation”. The electron-deficient B played synergetic roles to activate and stabilize the adsorbed N2 i.e. (i) It tunes the bandgap of CN for effective light absorption and charge transfer; (ii) The B-N coordination site polarizes chemisorbed N2 via electron pair acceptance; (iii) The filled sp2 orbital of B activates the N2 by π-back donation. Consequently, the photocatalytic performance of BCN-4 reaches 0.93mmolh−1g−1 with AQY of ∼13% (350 nm) and solar to NH3 conversion efficiency (SSCNH3) of 0.017%. The in situ DRIFT and DFT studies revealed that BCN exhibited spontaneous N2 adsorption and activation, followed by protonation of the adsorbed N2, with a negligible energy barrier.11Nsciescopu
Inductive Effect of Lewis Acidic Dopants on the Band Levels of Perovskite for a Photocatalytic Reaction
No full textBand-edge modulation of halide perovskites as photoabsorbers
plays
significant roles in the application of photovoltaic and photochemical
systems. Here, Lewis acidity of dopants (M) as the new descriptor
of engineering the band-edge position of the perovskite is investigated
in the gradiently doped perovskite along the core-to-surface (CsPbBr3–CsPb1–xMxBr3). Reducing M–bromide bond
strength with an increase in hardness of acidic M increases the electron
ability of basic Br, thus strengthening the Pb–Br orbital coupling
in M–Pb–Br, noted as the inductive effect of dopants.
Especially, the highly hard Lewis acidic Mg localized in the outer
position of the perovskite induces the increase of work function and
then shifts band edge upward along the core-to-surface of the perovskite.
Thus, charge separation driven by the dopant-induced internal electric
field induces the slow annihilation of the excited holes, improving
the slow aromatic Csp3–H dissociation
in the photocatalytic oxidation process by ∼211% (491.39 μmol
g–1 h–1) enhancements, compared
with undoped nanocrystals
Binder-free TiO2 hydrophilic film covalently coated by microwave treatment
No full textA binder-free attachment method for TiO2 on a substrate has been sought to retain high active photocatalysis. Here, we report a binder-free covalent coating of phase-selectively disordered TiO2 on a hydroxylated silicon oxide (SiO2) substrate through rapid microwave treatment. We found that Ti-O-Si and Ti-O-Ti bonds were formed through a condensation reaction between the hydroxyl groups of the disordered TiO2 and Si substrate, and the disordered TiO2 nanoparticles themselves, respectively. This covalent coating approach can steadily hold the active photocatalytic materials on the substrates and provide long-term stability. The binder-free disordered TiO2 coating film can have a thickness (above 38 mu m) with high surface integrity with a strong adhesion force (15.2 N) against the SiO2 substrate, which leads to the production of a rigid and stable TiO2 film. This microwave treated TiO2 coating film showed significant volatile organic compounds degradation abilities under visible light irradiation. The microwave coated selectively reduced TiO2 realized around 75% acetaldehyde degradation within 12 h and almost 90% toluene degradation after 9 h, also retains stable photodegradation performance during the cycling test. Thus, the microwave coating approach allowed the preparation of the binder-free TiO2 film as a scalable and cost-effective method to manufacture the TiO2 film that shows an excellent coating quality and strengthens the application as a photocatalyst under severe conditions.11Nsciescopu
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Discovering ultrahigh loading of single-metal-atoms via surface tensile-strain for unprecedented urea electrolysis
No full text© The Royal Society of Chemistry 2021. Single-atom-catalysts (SACs) have recently gained significant attention in energy conversion/storage applications, while the low-loading amount due to their easy-to-migrate tendency causes a major bottleneck. For energy-saving H-2 generation, replacing the sluggish oxygen evolution reaction with the thermodynamically favorable urea oxidation reaction (UOR) offers great promise, additionally mitigating the issue of urea-rich water contamination. However, the lack of efficient catalysts to overcome the intrinsically slow kinetics limits its scalable applications. Herein, we discover that incorporating tensile-strain on the surface of a Co3O4 (strained-Co3O4; S-Co3O4) support by the liquid N-2-quenching method can significantly inhibit the migration tendency of Rh single-atoms (Rh-SA), thereby stabilizing an similar to 200% higher loading of Rh-SA sites (Rh-SA-S-Co3O4; bulk loading similar to 6.6 wt%/surface loading similar to 11.6 wt%) compared to pristine-Co3O4 (P-Co3O4). Theoretical calculations revealed a significantly increased migration energy barrier of Rh-SA on the S-Co3O4 surface than on P-Co3O4, inhibiting their migration/agglomeration. Surprisingly, Rh-SA-S-Co3O4 exhibited exceptional pH-universal UOR activity, requiring record-low working potentials and surpassing Pt/Rh-C, this was due to superior urea adsorption and stabilization of CO*/NH* intermediates, revealed by DFT simulations. Meanwhile, the assembled urea-electrolyzer delivered 10 mA cm(-2) at only 1.33 V with robust stability in alkaline media. This work provides a general methodology towards high-loading SACs for scalable applications.11Nsciescopu
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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