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1.
Nat Mater ; 23(4): 552-559, 2024 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-38316979

RESUMEN

Developing active and stable atomically dispersed catalysts is challenging because of weak non-specific interactions between catalytically active metal atoms and supports. Here we demonstrate a general method for synthesizing atomically dispersed catalysts via photochemical defect tuning for controlling oxygen-vacancy dynamics, which can induce specific metal-support interactions. The developed synthesis method offers metal-dynamically stabilized atomic catalysts, and it can be applied to reducible metal oxides, including TiO2, ZnO and CeO2, containing various catalytically active transition metals, including Pt, Ir and Cu. The optimized Pt-DSA/TiO2 shows unprecedentedly high photocatalytic hydrogen evolution activity, producing 164 mmol g-1 h-1 with a turnover frequency of 1.27 s-1. Furthermore, it generates 42.2 mmol gsub-1 of hydrogen via a non-recyclable-plastic-photoreforming process, achieving a total conversion of 98%; this offers a promising solution for mitigating plastic waste and simultaneously producing valuable energy sources.

2.
J Am Chem Soc ; 146(18): 12556-12564, 2024 May 08.
Artículo en Inglés | MEDLINE | ID: mdl-38660792

RESUMEN

Transition metal nitride (TMN)-based nanostructures have emerged as promising materials for diverse applications in electronics, photonics, energy storage, and catalysis due to their highly desirable physicochemical properties. However, synthesizing TMN-based nanostructures with designed compositions and morphologies poses challenges, especially in the solution phase. The cation exchange reaction (CER) stands out as a versatile postsynthetic strategy for preparing nanostructures that are otherwise inaccessible through direct synthesis. Nevertheless, exploration of the CER in TMNs lags behind that in metal chalcogenides and metal phosphides. Here, we demonstrate cation exchange in colloidal metal nitride nanocrystals, employing Cu3N nanocrystals as starting materials to synthesize Ni4N and CoN nanocrystals. By controlling the reaction conditions, Cu3N@Ni4N and Cu3N@CoN core@shell heterostructures with tunable compositions can also be obtained. The Ni4N and CoN nanocrystals are evaluated as catalysts for the electrochemical oxygen evolution reaction (OER). Remarkably, CoN nanocrystals demonstrate superior OER performance with a low overpotential of 286 mV at 10 mA·cm-2, a small Tafel slope of 89 mV·dec-1, and long-term stability. Our CER approach in colloidal TMNs offers a new strategy for preparing other metal nitride nanocrystals and their heterostructures, paving the way for prospective applications.

3.
Macromol Rapid Commun ; 43(4): e2100709, 2022 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-34792255

RESUMEN

The effect of atomic substitution on the optoelectronic properties of a coplanar donor-acceptor (D-A) semiconducting polymer (SPs), prepared using cyclopentadithiophene (CDT) and 2,1,3-benzothiadiazole (BT) moieties, is investigated. By substituting a carbon atom in the BT unit with CF or C-Cl, two random D-A SPs are prepared, and their optoelectronic properties are thoroughly investigated. Density functional theory calculations demonstrate that the fluorinated polymer has a slightly smaller dihedral angle (Ï´ = 0.6°) than the pristine polymer (Ï´ = 1.9°) in its lowest-energy conformation, implying efficient charge transport through the coplanar backbone of the fluorinated polymer. However, the chlorinated polymer shows the lowest energy at a relatively larger dihedral angle (Ï´ = 139°) due to the steric hindrance induced by bulky chlorine atoms in the backbone, thereby leading to thin-film morphology, which is unfavorable for charge transport. Consequently, the fluorinated polymer yields the highest field-effect mobility (µ) of 0.57 cm2 V-1 s-1 , slightly higher than that of the pristine polymer (µ = 0.33 cm2 V-1 s-1 ), and the extended device lifetime of organic field-effect transistors over 12 d without any encapsulation layers. The results of this study provide design guidelines for air-stable D-A SPs.


Asunto(s)
Polímeros , Conformación Molecular
4.
Nano Lett ; 21(19): 7953-7959, 2021 Oct 13.
Artículo en Inglés | MEDLINE | ID: mdl-34585926

RESUMEN

Oxygen vacancies and their correlation with the electronic structure are crucial to understanding the functionality of TiO2 nanocrystals in material design applications. Here, we report spectroscopic investigations of the electronic structure of anatase TiO2 nanocrystals by employing hard and soft X-ray absorption spectroscopy measurements along with the corresponding model calculations. We show that the oxygen vacancies significantly transform the Ti local symmetry by modulating the covalency of titanium-oxygen bonds. Our results suggest that the altered Ti local symmetry is similar to the C3v, which implies that the Ti exists in two local symmetries (D2d and C3v) at the surface. The findings also indicate that the Ti distortion is a short-range order effect and presumably confined up to the second nearest neighbors. Such distortions modulate the electronic structure and provide a promising approach to structural design of the TiO2 nanocrystals.

5.
J Am Chem Soc ; 143(14): 5386-5395, 2021 Apr 14.
Artículo en Inglés | MEDLINE | ID: mdl-33725440

RESUMEN

Pd is one of the most effective catalysts for the electrochemical reduction of CO2 to formate, a valuable liquid product, at low overpotential. However, the intrinsically high CO affinity of Pd makes the surface vulnerable to CO poisoning, resulting in rapid catalyst deactivation during CO2 electroreduction. Herein, we utilize the interaction between metals and metal-organic frameworks to synthesize atomically dispersed Au on tensile-strained Pd nanoparticles showing significantly improved formate production activity, selectivity, and stability with high CO tolerance. We found that the tensile strain stabilizes all reaction intermediates on the Pd surface, whereas the atomically dispersed Au selectively destabilizes CO* without affecting other adsorbates. As a result, the conventional COOH* versus CO* scaling relation is broken, and our catalyst exhibits 26- and 31-fold enhancement in partial current density and mass activity toward electrocatalytic formate production with over 99% faradaic efficiency, compared to Pd/C at -0.25 V versus RHE.

6.
Nat Mater ; 19(4): 436-442, 2020 04.
Artículo en Inglés | MEDLINE | ID: mdl-31932671

RESUMEN

Despite the growing demand for hydrogen peroxide it is almost exclusively manufactured by the energy-intensive anthraquinone process. Alternatively, H2O2 can be produced electrochemically via the two-electron oxygen reduction reaction, although the performance of the state-of-the-art electrocatalysts is insufficient to meet the demands for industrialization. Interestingly, guided by first-principles calculations, we found that the catalytic properties of the Co-N4 moiety can be tailored by fine-tuning its surrounding atomic configuration to resemble the structure-dependent catalytic properties of metalloenzymes. Using this principle, we designed and synthesized a single-atom electrocatalyst that comprises an optimized Co-N4 moiety incorporated in nitrogen-doped graphene for H2O2 production and exhibits a kinetic current density of 2.8 mA cm-2 (at 0.65 V versus the reversible hydrogen electrode) and a mass activity of 155 A g-1 (at 0.65 V versus the reversible hydrogen electrode) with negligible activity loss over 110 hours.

7.
J Am Chem Soc ; 142(33): 14190-14200, 2020 Aug 19.
Artículo en Inglés | MEDLINE | ID: mdl-32787259

RESUMEN

Compared to nanostructured platinum (Pt) catalysts, ordered Pt-based intermetallic nanoparticles supported on a carbon substrate exhibit much enhanced catalytic performance, especially in fuel cell electrocatalysis. However, direct synthesis of homogeneous intermetallic alloy nanocatalysts on carbonaceous supports with high loading is still challenging. Herein, we report a novel synthetic strategy to directly produce highly dispersed MPt alloy nanoparticles (M = Fe, Co, or Ni) on various carbon supports with high catalyst loading. Importantly, a unique bimetallic compound, composed of [M(bpy)3]2+ cation (bpy = 2,2'-bipyridine) and [PtCl6]2- anion, evenly decomposes on carbon surface and forms uniformly sized intermetallic nanoparticles with a nitrogen-doped carbon protection layer. The excellent oxygen reduction reaction (ORR) activity and stability of the representative reduced graphene oxide (rGO)-supported L10-FePt catalyst (37 wt %-FePt/rGO), exhibiting 18.8 times higher specific activity than commercial Pt/C catalyst without degradation over 20 000 cycles, well demonstrate the effectiveness of our synthetic approach toward uniformly alloyed nanoparticles with high homogeneity.

8.
J Am Chem Soc ; 142(31): 13406-13414, 2020 Aug 05.
Artículo en Inglés | MEDLINE | ID: mdl-32608979

RESUMEN

Integrated with heat-generating devices, a Li-ion battery (LIB) often operates at 20-40 °C higher than the ordinary working temperature. Although macroscopic investigation of the thermal contribution has shown a significant reduction in the LIB performance, the molecular level structural and chemical origin of battery aging in a mild thermal environment has not been elucidated. On the basis of the combined experiments of the electrochemical measurements, Cs-corrected electron microscopy, and in situ analyses, we herein provide operando structural and chemical insights on how a mild thermal environment affects the overall battery performance using anatase TiO2 as a model intercalation compound. Interestingly, a mild thermal condition induces excess lithium intercalation even at near-ambient temperature (45 °C), which does not occur at the ordinary working temperature. The anomalous intercalation enables excess lithium storage in the first few cycles but exerts severe intracrystal stress, consequently cracking the crystal that leads to battery aging. Importantly, this mild thermal effect is accumulated upon cycling, resulting in irreversible capacity loss even after the thermal condition is removed. Battery aging at a high working temperature is universal in nearly all intercalation compounds, and therefore, it is significant to understand how the thermal condition contributes to battery aging for designing intercalation compounds for advanced battery electrode materials.

9.
Nat Mater ; 18(6): 620-626, 2019 06.
Artículo en Inglés | MEDLINE | ID: mdl-31011217

RESUMEN

The reversible and cooperative activation process, which includes electron transfer from surrounding redox mediators, the reversible valence change of cofactors and macroscopic functional/structural change, is one of the most important characteristics of biological enzymes, and has frequently been used in the design of homogeneous catalysts. However, there are virtually no reports on industrially important heterogeneous catalysts with these enzyme-like characteristics. Here, we report on the design and synthesis of highly active TiO2 photocatalysts incorporating site-specific single copper atoms (Cu/TiO2) that exhibit a reversible and cooperative photoactivation process. Our atomic-level design and synthetic strategy provide a platform that facilitates valence control of co-catalyst copper atoms, reversible modulation of the macroscopic optoelectronic properties of TiO2 and enhancement of photocatalytic hydrogen generation activity, extending the boundaries of conventional heterogeneous catalysts.

10.
J Am Chem Soc ; 140(48): 16676-16684, 2018 Dec 05.
Artículo en Inglés | MEDLINE | ID: mdl-30418777

RESUMEN

Various kinds of nanostructured materials have been extensively investigated as lithium ion battery electrode materials derived from their numerous advantageous features including enhanced energy and power density and cyclability. However, little is known about the microscopic origin of how nanostructures can enhance lithium storage performance. Herein, we identify the microscopic origin of enhanced lithium storage in anatase TiO2 nanostructure and report a reversible and stable route to achieve enhanced lithium storage capacity in anatase TiO2. We designed hollow anatase TiO2 nanostructures composed of interconnected ∼5 nm sized nanocrystals, which can individually reach the theoretical lithium storage limit and maintain a stable capacity during prolonged cycling (i.e., 330 mAh g-1 for the initial cycle and 228 mAh g-1 for the 100th cycle, at 0.1 A g-1). In situ characterization by X-ray diffraction and X-ray absorption spectroscopy shows that enhanced lithium storage into the anatase TiO2 nanocrystal results from the insertion reaction, which expands the crystal lattice during the sequential phase transition (anatase TiO2 → Li0.55TiO2 → LiTiO2). In addition to the pseudocapacitive charge storage of nanostructures, our approach extends the utilization of nanostructured TiO2 for significantly stabilizing excess lithium storage in crystal structures for long-term cycling, which can be readily applied to other lithium storage materials.

11.
Angew Chem Int Ed Engl ; 57(41): 13629-13634, 2018 Oct 08.
Artículo en Inglés | MEDLINE | ID: mdl-30133093

RESUMEN

To understand the effects rendered on the relevant basic physical properties and device function by controlling the regiochemistry of the cyclopenta[1,2-b:5,4-b']dithiophene-fluorobenzo[c][1,2,5]thiadiazole polymer (hereafter referred to as the CDT-FBT polymer), two polymers, the regiorandom polymer (RA) and regioregular version (RR), respectively, are synthesized and characterized. In addition, an efficient route for synthesizing a key monomer for RR using various synthesis scope and optimizing the reaction conditions is discussed. Although RA exhibits optical, electrochemical, and morphological properties similar to RR, it shows better field-effect transistor (FET) performance. Surprisingly, by employing a capillarity-mediated sandwich-casting process on a nanogrooved substrate, an unprecedented mobility of 17.8 cm2 V-1 s-1 is obtained for RA-based FETs; this mobility value is almost twofold greater than those of the corresponding RR-based FETs. For the first time, this study challenges previously reported results in that high carrier mobility is related to the high degree of polymer order induced by the backbone regioregularity.

12.
Thorax ; 72(3): 263-270, 2017 03.
Artículo en Inglés | MEDLINE | ID: mdl-27553224

RESUMEN

BACKGROUND: Uncontrolled diabetes, unlike controlled diabetes, is associated with an impaired immune response. However, little is known about the impact of the status of diabetes control on clinical features and treatment outcomes in patients with pulmonary TB (PTB). We conducted this study to evaluate whether the status of diabetes control influences clinical manifestations and treatment responses in PTB. METHODS: A multicentre prospective study was performed between September 2012 and September 2014. The patients were categorised into three groups according to the glycated haemoglobin (HbA1C) level: PTB without diabetes mellitus (non-DM), PTB with controlled diabetes (controlled-DM) and PTB with uncontrolled diabetes (uncontrolled-DM). The primary outcome was the sputum culture conversion rate after 2 months of intensive treatment. RESULTS: Among 661 patients with PTB, 157 (23.8%) had diabetes and 108 (68.8%) had uncontrolled diabetes (HbA1C≥7.0%). The uncontrolled-DM group exhibited more symptoms, positive sputum smears (p<0.001) and presence of cavities (p<0.001) than the non-DM group. Regarding treatment responses, patients with uncontrolled-DM were more likely to have a positive culture after 2 months (p=0.009) and either treatment failure (p=0.015) or death (p=0.027) compared with the non-DM group. In contrast, those with controlled-DM showed similar treatment responses to the non-DM group. In multivariable analysis, uncontrolled diabetes was an independent risk factor for a positive sputum culture after 2 months of treatment (adjusted OR, 2.11; p=0.042) and either treatment failure or death (adjusted OR, 4.11; p=0.022). CONCLUSIONS: Uncontrolled diabetes is an independent risk factor for poor treatment response in PTB.


Asunto(s)
Antituberculosos/uso terapéutico , Diabetes Mellitus/prevención & control , Tuberculosis Pulmonar/tratamiento farmacológico , Adolescente , Adulto , Anciano , Femenino , Humanos , Masculino , Persona de Mediana Edad , Pronóstico , Estudios Prospectivos , República de Corea , Factores de Riesgo , Resultado del Tratamiento
13.
Nano Lett ; 16(1): 314-9, 2016 Jan 13.
Artículo en Inglés | MEDLINE | ID: mdl-26645364

RESUMEN

We report the controlled nanomorphology of semiconducting polymers on chemically and mechanically stable nanogrooved polymer substrates. By employing silicon dioxide thin films with finely adjusted thicknesses on nanogrooved polymer substrates, semiconducting polymer thin films oriented and aligned along the nanogrooves were obtained. Organic field-effect transistors (OFETs) fabricated from the oriented semiconducting polymer, poly[4-(4,4-dihexadecyl-4H-cyclopenta[1,2-b:5,4-b']dithiophen-2-yl)-alt-[1,2,5]thiadiazolo-[3,4-c]pyridine] (PCDTPT), yielded saturation hole mobilities as high as 19.3 cm(2) V(-1 )s(-1), and the flexible "plastic" transistors demonstrated excellent mechanical stability under various bending conditions. These results represent important progress for solution-processed flexible OFETs and demonstrate that directed self-assembly of semiconducting polymers can be achieved by soft nanostructures.

14.
Nano Lett ; 16(10): 6709-6715, 2016 10 12.
Artículo en Inglés | MEDLINE | ID: mdl-27673480

RESUMEN

Despite the need for molecularly smooth self-assembled monolayers (SAMs) on silicon dioxide surfaces (the most common dielectric surface), current techniques are limited to nonideal silane grafting. Here, we show unique bioinspired zwitterionic molecules forming a molecularly smooth and uniformly thin SAM in "water" in <1 min on various dielectric surfaces, which enables a dip-coating process that is essential for organic electronics to become reality. This monomolecular layer leads to high mobility of organic field-effect transistors (OFETs) based on various organic semiconductors and source/drain electrodes. A combination of experimental and computational techniques confirms strong adsorption (Wad > 20 mJ m-2), uniform thickness (∼0.5 or ∼1 nm) and orientation (all catechol head groups facing the oxide surface) of the "monomolecular" layers. This robust (strong adsorption), rapid, and green SAM represents a promising advancement toward the next generation of nanofabrication compared to the current nonuniform and inconsistent polysiloxane-based SAM involving toxic chemicals, long processing time (>10 h), or heat (>80 °C).

15.
Uisahak ; 25(3): 407-444, 2016 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-28529300

RESUMEN

This article aims to evaluate and analyze the description of the modern hospital as history record, which appeared in YI Kwang Su's novel Love. This novel has mentioned in detail western style clinic, Bukgando Catholic hospital, tuberculosis sanitarium as its main space. Modern hospitals are depicted in the novel has a great significance in historical aspect as well as in literary aspect. The most data on modern hospital is laws, statistics and newspaper archives. These materials are a great help to understand the history and status of the modern hospital. Literary description here is important materials, that specific to reconstruct the appearance of the modern hospital at that time. Literary representations infuse life into the history record. In this regard, Love has special meaning in the history of Korean modern literature. Before anything else, doctor AN Bin's clinic as a first space of the novel vividly shows the reality of the Western style clinic and a general practitioner under the colonial period. The establishment of the hospital was based on 「Rules on private hospital」 declared by the Japanese Government General of Korea in 1919. According to this Rules, a private clinic's founder had to submit the documents to the director of police affairs, in which all the details were written. It included name of hospital, site location and size, floor plan of a nearby building, each size of patient's rooms, number of steps and emergency exit, bath, toilet, disinfecting room. AN Bin's clinic was a private hospital with the requirements in the rules. The descriptions of this clinic re-created real situation of private hospitals, specifically scale of hospital, interior space, conditions of patient's room at the time. The second modern hospital in the novel is Bukgando Catholic hospital. There is a lot more materials on medical activity and hospital of protestant churches than we thought. But we do not have a lot of information on catholic church's medical activities and hospital. In this respect, Bukgando Catholic hospital in Love has a great value as historical material. The medical activity of catholic churches was weak than protestant's one under the japanese colonial period. But there were catholic church's medical activities and hospitals. The catholic church's professional medical activities are mainly deployed since the 1930s in earnest, especially Bukgando Catholic hospital played an important role. The catholic hospital in this novel is valuable material to understand medical activities of catholic church. Third form of the modern hospital described in the Love is tuberculosis sanitarium. WADA Tomomi maintained that the model of Bukhan sanitarium was Kyeongseong sanitarium, that was established by the seventh-day adventist in 1936. She thinks, that the adventist church's treatment is similar to Bukhan sanitarium's. The therapy of the adventist church, however, was common from tuberculosis treatment at the time and AN Bin was not adventist. And WADA Tomomi said that 'ozone' therapy of Bukhan sanitarium came from Kyeongseong sanitarium. But we can find this therapy in Haeju sanitarium. In this respect, AN Bin's sanitarium is similar to Haeju sanitarium. YI Kwang Su had not modeled his Bukhan sanitarium on certain sanitarium. He had integrated the materials on sanitarium and envisioned Bukhan sanitarium. Here Haeju sanitarium played important role than Kyeongseong sanitarium. In conclusion, Love has a special meaning as an important historical material, that restore and understand the history of the modern hospital. Literature is worth as a record of the society. In particular, novel infuses human breath into the history record, as if we can see the motion picture.


Asunto(s)
Hospitales/historia , Literatura Moderna/historia , Medicina en la Literatura , Catolicismo , Colonialismo , Historia del Siglo XX , Japón , Protestantismo , República de Corea
16.
Pathol Res Pract ; 253: 155035, 2024 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-38171080

RESUMEN

The present study aimed to investigate the clinicopathological and prognostic implications of the cribriform pattern in lung adenocarcinoma through a meta-analysis. The estimated rates of cribriform pattern in lung adenocarcinomas were investigated. The correlations between cribriform pattern and clinicopathological characteristics, including genetic alterations and prognosis were evaluated. The estimated rate of cribriform pattern was 0.150 (95% confidence interval [CI], 0.101-0.218) in lung adenocarcinoma. The estimated rates of cribriform pattern in the 5% and 10% criteria were 0.230 (95% CI 0.125-0.386) and 0.130 (95% CI 0.062-0.252), respectively. The presence of cribriform pattern was significantly correlated with larger tumor size (> 30 mm), spread through air spaces, and lymph node metastasis (P < 0.001, P < 0.001, and P = 0.007, respectively, in the meta-regression test). There were no significant differences between cribriform pattern, smoking history, and vascular and lymphatic invasion. In lung adenocarcinoma with cribriform pattern, the estimated rates of ALK rearrangement, KRAS, and EGFR mutations were 0.407 (95% CI 0.165-0.704), 0.330 (95% CI 0.117-0.646), and 0.249 (95% CI 0.125-0.437), respectively. ALK rearrangement was significantly more frequent in lung adenocarcinomas with cribriform pattern than in those without. The overall survival rate was significantly worse in lung adenocarcinomas with a cribriform pattern than in those without (hazard ratio 2.051, 95% CI 1.369-3.075). In conclusion, the presence of a cribriform pattern can be a useful predictor of the clinicopathological characteristics and prognosis of patients with lung adenocarcinoma.


Asunto(s)
Adenocarcinoma del Pulmón , Adenocarcinoma , Neoplasias Pulmonares , Humanos , Neoplasias Pulmonares/patología , Adenocarcinoma/patología , Adenocarcinoma del Pulmón/genética , Adenocarcinoma del Pulmón/patología , Pronóstico , Mutación , Proteínas Tirosina Quinasas Receptoras/genética , Estadificación de Neoplasias
17.
Nanoscale ; 16(26): 12329-12344, 2024 Jul 04.
Artículo en Inglés | MEDLINE | ID: mdl-38860477

RESUMEN

Achieving atomic precision in nanostructured materials is essential for comprehending formation mechanisms and elucidating structure-property relationships. Within the realm of nanoscience and technology, atomically precise ligand-protected noble metal nanoclusters (NCs) have emerged as a rapidly expanding area of interest. These clusters manifest quantum confinement-induced optoelectronic, photophysical, and chemical properties, along with remarkable catalytic capabilities. Among coinage metals, silver distinguishes itself for the fabrication of stable nanoclusters, primarily due to its cost-effectiveness compared to gold. This minireview provides an overview of recent advancements since 2020 in synthetic methodologies and ligand selections toward attaining NCs boasting a minimum of two free valence electrons. Additionally, it explores strategies for fine-tuning optical properties. The discussion extends to surface reactivity, elucidating how exposure to ligands, heat, and light induces transformations in size and structure. Of paramount significance are the applications of silver NCs in catalytic reactions for energy and chemical conversion, supplemented by in-depth mechanistic insights. Furthermore, the review delineates challenges and outlines future directions in the NC field, with an eye toward the design of new functional materials and prospective applications in diverse technologies, including optoelectronics, energy conversion, and fine chemical synthesis.

18.
Nat Commun ; 15(1): 2995, 2024 Apr 06.
Artículo en Inglés | MEDLINE | ID: mdl-38582773

RESUMEN

Improving the kinetics and selectivity of CO2/CO electroreduction to valuable multi-carbon products is a challenge for science and is a requirement for practical relevance. Here we develop a thiol-modified surface ligand strategy that promotes electrochemical CO-to-acetate. We explore a picture wherein nucleophilic interaction between the lone pairs of sulfur and the empty orbitals of reaction intermediates contributes to making the acetate pathway more energetically accessible. Density functional theory calculations and Raman spectroscopy suggest a mechanism where the nucleophilic interaction increases the sp2 hybridization of CO(ad), facilitating the rate-determining step, CO* to (CHO)*. We find that the ligands stabilize the (HOOC-CH2)* intermediate, a key intermediate in the acetate pathway. In-situ Raman spectroscopy shows shifts in C-O, Cu-C, and C-S vibrational frequencies that agree with a picture of surface ligand-intermediate interactions. A Faradaic efficiency of 70% is obtained on optimized thiol-capped Cu catalysts, with onset potentials 100 mV lower than in the case of reference Cu catalysts.

19.
Nat Nanotechnol ; 19(3): 311-318, 2024 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-37996517

RESUMEN

The electrochemical reduction of CO2 in acidic conditions enables high single-pass carbon efficiency. However, the competing hydrogen evolution reaction reduces selectivity in the electrochemical reduction of CO2, a reaction in which the formation of CO, and its ensuing coupling, are each essential to achieving multicarbon (C2+) product formation. These two reactions rely on distinct catalyst properties that are difficult to achieve in a single catalyst. Here we report decoupling the CO2-to-C2+ reaction into two steps, CO2-to-CO and CO-to-C2+, by deploying two distinct catalyst layers operating in tandem to achieve the desired transformation. The first catalyst, atomically dispersed cobalt phthalocyanine, reduces CO2 to CO with high selectivity. This process increases local CO availability to enhance the C-C coupling step implemented on the second catalyst layer, which is a Cu nanocatalyst with a Cu-ionomer interface. The optimized tandem electrodes achieve 61% C2H4 Faradaic efficiency and 82% C2+ Faradaic efficiency at 800 mA cm-2 at 25 °C. When optimized for single-pass utilization, the system reaches a single-pass carbon efficiency of 90 ± 3%, simultaneous with 55 ± 3% C2H4 Faradaic efficiency and a total C2+ Faradaic efficiency of 76 ± 2%, at 800 mA cm-2 with a CO2 flow rate of 2 ml min-1.

20.
ACS Appl Mater Interfaces ; 15(8): 10926-10935, 2023 Mar 01.
Artículo en Inglés | MEDLINE | ID: mdl-36797035

RESUMEN

Zinc oxide nanoparticle (ZnO-NP) thin films have been intensively used as electron transport layers (ETLs) in organic optoelectronic devices, but their moderate mechanical flexibility hinders their application to flexible electronic devices. This study reveals that the multivalent interaction between ZnO-NPs and multicharged conjugated electrolytes, such as diphenylfluorene pyridinium bromide derivative (DFPBr-6), can significantly improve the mechanical flexibility of ZnO-NP thin films. Intermixing ZnO-NPs and DFPBr-6 facilitates the coordination between bromide anions (from the DFPBr-6) and zinc cations on ZnO-NP surfaces, forming Zn2+-Br- bonds. Different from a conventional electrolyte (e.g., KBr), DFPBr-6 with six pyridinium ionic side chains holds the Br--chelated ZnO-NPs adjacent to DFP+ through Zn2+-Br--N+ bonds. Consequently, ZnO-NP:DFPBr-6 thin films exhibit improved mechanical flexibility with a critical bending radius as low as 1.5 mm under tensile bending conditions. Flexible organic photodetectors with ZnO-NP:DFPBr-6 thin films as ETLs demonstrate reliable device performances with high R (0.34 A/W) and D* (3.03 × 1012 Jones) even after 1000 times repetitive bending at a bending radius of 4.0 mm, whereas devices with ZnO-NP and ZnO-NP:KBr ETLs yield >85% reduction in R and D* under the same bending condition.

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