Layered transition metal dichalcogenide (TMD) nanomaterials are promising alternatives to platinum (Pt) for the hydrogen evolution reaction (HER). However, the family of layered TMDs is mainly ...limited to Group IV–VII transition metals, while the synthesis of layered TMDs based on metals from other groups still remains a challenge. Herein, we demonstrate by atomic‐resolution transmission electron microscopy that hexagonal RuSe2 (h‐RuSe2) nanosheets with a mixture of 2H and 1T phases can be obtained by a facile bottom‐up colloidal synthetic approach. The obtained h‐RuSe2, which can be transformed into the thermodynamically favorable phase of cubic RuSe2 (c‐RuSe2) only after annealing at 600 °C, exhibits Pt‐like HER performance, with a fivefold turnover frequency enhancement compared to the c‐RuSe2 in alkaline media. Experimental results and density functional theory (DFT) calculations reveal that the enhanced adsorption free energies of H2O (ΔGH2O*
), optimized adsorption free energies of H (ΔGH*), and increased conductivity of h‐RuSe2 contribute to its superior HER activity.
Hexagonal RuSe2 nanosheets (h‐RuSe2), including 2H and 1T phases, are prepared in a one‐pot colloidal synthesis. This new member of the family of layered transition metal dichalcogenides (TMDs) displays significantly enhanced HER performance. The structural phase change from h‐RuSe2 to cubic RuSe2 takes place upon annealing at 600 °C. This is a significant step forward in expanding the family of layered TMDs.
In the aim to develop the field of low cost materials for highly efficient hydrogen evolution electro-catalysis, photo-catalysis, and low cost solar cells applications, thin films of transition metal ...dichalcogenide materials (RuSe2, FeSe2, RuS2, FeS2, ….etc) are promising candidates especially. Indeed, thin films of transition metal dichalcogenide (TMD) materials, such as RuSe2, are promising alternatives to platinum (Pt) for the hydrogen evolution reaction (HER). Herein, growth of RuSe2 thin films, having desired properties for several applications, using the simple and non-cost technique, spray pyrolysis, makes the main object of this work. In a first step, an aqueous solution of RuCl3.3H2O (0.03 M) was sprayed for 5 min onto ordinary glass substrates pre-heated at 350 °C. Dark amorphous thin films were obtained. In a second step, the as obtained amorphous thin films were heat treated under selenium atmosphere (∼10−4Pa) at various temperatures (450, 500, and 550 °C) for 3 h in RTP oven. A single hexagonal RuSe2-phase (h-RuSe2) was picked up by the XRD analysis. The obtained layers presented a high absorption coefficient (α > 6x104cm−1 for the layers selenized at 450 °C, and α > 106cm−1, λ < 1000 nm for the layers selenized at 500 and 550 °C). The plots of (α.h.ν)2 vs (h.ν) showed direct band gaps corresponding to the photon energies of about 1.56 eV, 1.75 eV, and 1.86 eV of the layers selenized at 450, 500, and 550 °C, simultaneously. The surfuce morphology was treated by SEM: clustred structure was observed for the layers obtained after selenization at 450 °C, and grannular structures were observed for the layers obtained at 500 and 550 °C. The grain size becomes so large for the layers obtained at 550 °C; that confirms their high absorbance. The interesting obtained results provide for improving more the domain of low cost materials having encouraging properties for several applications domains (photovoltaic, hydrogen evolution, electrocatalysis and photocatalysis) using the spay pyrolysis technique.
Selenium is a non-metallic element of group IV, with relatively small electronegativity and high conductivity. Metal selenides show good capacitive properties, and the capacitive performance of RuSe2 ...is few reported. In this work, RuSe2 @ 250 nanoparticles are prepared at a temperature of 250 °C under N2 atmosphere, and those further calcined at 550 and 800 °C are defined as RuSe2 @ 550 and RuSe2 @ 800. The results show that RuSe2 @ 250 is in amorphous structures, RuSe2 @ 800 is in crystalline forms, and RuSe2 @ 550 is in between them. Different structures also make difference in their capacitance performances. Amorphous RuSe2 @ 250 has high specific capacitance (1123.9 F g−1 at 0.5 A g−1) and high specific energy, but low cyclic stability and low rate capacity. RuSe2 @ 800 has lower specific capacitance but higher cyclic stability, and RuSe2 @ 550 is still in the between. Based on these results, a structure-dependent charge transfer mechanism is proposed. Further, an asymmetric supercapacitor with RuSe2 @ 550 as the anode and conducting carbon as the cathode is assembled. It shows the specific energy of 44.8 Wh kg−1 at the specific power of 400 W kg−1 and good cyclic stability of 96.2% capacitance retention after 2000 cycles, indicating that RuSe2 has a potential application prospect for electrochemical energy storage.
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La détresse existentielle, qui est le grand thème de la littérature romantique, comporte une méfiance à l’égard du pouvoir de la vérité, une méfiance à l’égard de la possibilité que celle-ci ...s’affirme dans le monde réel. Il s’agit d’une constante puissante qui à cette époque envahit le domaine entier de la littérature de façon obsessionnelle. Cet article retrouve cette constante, à partir de l’héritage rousseauiste, dans quelques ouvrages de Constant, Cottin, Mérimée, Musset, Stendhal et Balzac. Le mensonge, la méprise, le stratagème corrompent les relations personnelles et sociales et le dévoilement de la vérité n’arrive pas à les recomposer : il a toujours une issue tragique.
The existential sadness, which is the great theme of Romantic literature, implies a mistrust towards the power of truth, a mistrust towards the possibility that this truth could assert itself in the ...real world. It is a powerful constant that at this time comes over the whole field of literature in an obsessive way. Starting from Rousseau’s heritage, this article finds this constant in some works of Constant, Cottin, Mérimée, Musset, Stendhal and Balzac. The lie, the misunderstanding, the ruse corrupt social and personal relationships and the disclosure of the truth does not manage to restore them: it always has a tragic outcome.
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•Simultaneous heteroatom doping and vacancy engineering was integrated to modify RuSe2.•Low-valence Cu doping enriched the Se vacancy and regulated the electronic structure.•Enhanced ...HER activity was achieved for the proposed Cu-RuSe2@C electrocatalyst.•Self-powered system was assembled to drive water splitting for hydrogen coproduction.
Heteroatom doping and vacancy engineering play vital roles in designing a high-activity electrocatalyst. Herein, we proposed a novel enriched Se vacancies engineering of the promising ruthenium chalcogenide of RuSe2 induced by low-valence Cu doping for promoting hydrogen evolution reaction (HER) electrocatalysis in alkaline media. The Cu-doped RuSe2 with enriched Se vacancies supported on graphitized carbon (Cu-RuSe2@C) was synthesized by a simple one-step selenization of bimetallic MOF precursor of Ru/Cu-BTC (1,3,5-benzenetricarboxylic acid) polyhedra. Compared to the Cu(Ⅱ)-dominant doped RuSe2 (CuⅡ/Ⅰ-RuSe2@C) with deficient Se vacancies, the proposed Cu(Ⅰ)-dominant doped RuSe2 (CuⅠ/Ⅱ-RuSe2@C) with enriched Se vacancies exhibited significantly improved electrocatalytic activity, which was potentially derived from the created electron-deficient Ruδ+ and Seν− sites induced by low-valence Cu doping. Specifically, CuⅠ/Ⅱ-RuSe2@C needed only 40 mV overpotential to drive a HER current density of 10 mA cm−2, comparable to commercial Pt/C (38 mV) and much lower than those of CuⅡ/Ⅰ-RuSe2@C (93 mV) and RuSe2@C (362 mV). Furthermore, an alkaline Zn-H2O fuel cell with a CuⅠ/Ⅱ-RuSe2@C cathode was integrated to demonstrate its potential applications, which delivered a maximum power density of 15.1 mW cm−2 and specific capacitance of 660 mAh g−1 with good stability. Two series-connected alkaline Zn-H2O cells acted as a chemical energy converter for simultaneous electricity generation and hydrogen coproduction by driving the coupled water splitting.
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•A RuSe2/MoSe2 heterostructure was prepared for HER in alkaline media.•RuSe2 nanoparticles was uniformly dispersed onto MoSe2 rods.•The charge redistribution over interface of ...RuSe2/MoSe2 facilitated charge transfer.•The RuSe2/MoSe2 heterostructure exhibited good performance for HER in alkaline media.•DFT was performed to investigate the mechanism behind performance improvement.
Despite being regarded as a favorable substitute for platinum-based catalysts in hydrogen evolution reaction (HER), molybdenum diselenide (MoSe2) exhibits inferior electrocatalytic performance due to its inadequate conductivity and limited active sites. However, employing molecular engineering for modification holds great potential in significantly enhancing its performance, yet it still poses significant challenges. Herein, an interface engineering strategy was adopted to obtain RuSe2 modified MoSe2 composite catalysts (RuSe2/MoSe2). In alkaline media, RuSe2/MoSe2 exhibited a reduced overpotential of 147.8 mV at 10 mA cm−2 comparing with pristine MoSe2 (351.8 mV). Experimental findings and density functional theory (DFT) calculations indicated that increased conductivity, enhanced hydrophily and optimized adsorption free energies of hydrogen contribute to its enhanced HER activity. This work opens up an interface engineering strategy for designing more efficient selenide-based electrocatalysts.
Photocatalytic hydrogen production is identified as a prospective route for solving the energy crisis and reducing environmental pollution. However, the complexation of photogenic carriers and the ...lack of active sites hinder the efficiency of photocatalysis. The piezoelectric effect and the corporation of cocatalyst are considered as effective strategies to facilitate the separation of the photogenic charge carriers. Ru-based compounds such as RuSe2, RuTe2, RuS2 and their derivatives are considered as potentially alternative catalysts to the platinum cocatalyst for the hydrogen evolution realution. Herein, we prepare a novel RuSe2/CdS piezo-photocatalysts in which RuSe2 cocatalyst is synthesized by microwave method to enable efficient piezo-photocatalytic hydrogen production. The experimental results show that the hydrogen production efficiency of 1.5% RuSe2/CdS is 63.857 μmol/mg/h under solar and ultrasonic conditions, which is about 7.54 times that of pure CdS (8.468 μmol/mg/h). More importantly, the hydrogen production efficiency of 1.5% RuSe2/CdS is remain stable after seven cycles of experiments. The enhanced piezo-photocatalytic activity is attributed to the interaction and the matching energy bands between RuSe2 and CdS, which facilitates photogenic electrons extend from CdS to RuSe2 cocatalyst. This work exposes a prospect for improving photocatalytic performance, and achieving efficient piezo-photocatalysis by using mechanical energy.
•Stable and different proportions of RuSe2/CdS catalysts are fabricated.•RuSe2 exhibits good electrical conductivity and abundant active sites.•RuSe2/CdS shows remarkably enhanced piezo-photocatalytic HER activity.•Such an H2 production rate exceeds all reported RuSe2-based photocatalysts.
The current photocatalytic efficiency is greatly limited owing to severe electron-hole (e--h+) pair recombination. Finding inexpensive and highly active cocatalysts is an efficacious tactics for ...improve photocatalytic capability. Noble metal cocatalysts could significantly improve the photocatalytic efficiency of semiconductors. However, precious metals are too expensive to be used on a large scale. Herein, a novel highly efficient crystalline RuSe2 cocatalyst is reported and loaded on Black-TiO2 to form RuSe2/Black-TiO2 heterostructure. As far as we know, RuSe2 has not been documented as a fast electron-based photocatalytic cocatalyst trapping for photocatalytic degradation. The degradation rate of rhodamine B (RhB) by 0.5% RuSe2/Black-TiO2 reaches up to 97.23% within 60 min, while that of pure Black-TiO2 is only 60.53%. Additionally, RuSe2/Black-TiO2 has the advantages of narrow band gap, more active sites and better conductivity compared with pure Black-TiO2. Capture experiments and EPR experiments show that superoxide radicals are the main active species in 0.5% RuSe2/Black-TiO2.
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•A novel and efficient photocatalyst RuSe2/Black-TiO2 is successfully synthesized for the first time.•0.5 wt % RuSe2/Black-TiO2 reached degradation efficiency of 97.23% in 60 min, which is 1.61 times that of Black-TiO2.•The reasonable photocatalytic mechanism for RuSe2/Black-TiO2 is proposed.
Certeau on the Run Daniel Ellwanger
Tr@jectoires (Paris),
06/2022, Volume:
15
Journal Article
Open access
Cet article examine l’étude ethnographique On the Run d’Alice Goffman, en explorant des usages littéraires et narratifs de l’écriture qui semblent habituellement étrangers aux textes sociologiques. ...Ce faisant l’article interroge les tensions qui résultent de ces emplois. En s’appuyant sur les réflexions de Michel de Certeau dans les Arts de faire, l’article argumente qu’il est possible de décrire les ruses quotidiennes et les pratiques fugitives que le regard de la théorie sociologique a l’habitude d’invisibiliser. Ainsi l’article interroge le potentiel des procédures narratives et littéraires pour l’écriture sociologique et leur crédibilité ethnographique.
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