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1.
Molecules ; 28(9)2023 Apr 29.
Artigo em Inglês | MEDLINE | ID: mdl-37175219

RESUMO

Glioblastoma (GBM) is an incurable primary brain tumor with a poor prognosis. Resection, radiation therapy, and temozolomide (TMZ) are insufficient to increase survival, making the treatment limited. Thus, the search for more effective and specific treatments is essential, making plants a promising source for elucidating new anti-glioblastoma compounds. Accordingly, this study investigated the effects of four fractions of hexane and ethyl acetate extract of Annona coriacea Mart., enriched with acetogenins, against GBM cell lines. All four fractions were selectively cytotoxic to GBM cells when compared to TMZ. Moreover, A. coriacea fractions delayed cell migration; reduced cytoplasmic projections, the metalloproteinase 2 (MMP-2) activity; and induced morphological changes characteristic of necroptosis, possibly correlated with the increase in receptor-interacting protein kinase 1 and 3 (RIP-1 and RIP-3), apoptosis-inducing factor (AIF), and the non-activation of cleaved caspase 8. The present findings reinforce that fractions of A. coriacea Mart. should be considered for more studies focusing treatment of GBM.


Assuntos
Annona , Neoplasias Encefálicas , Glioblastoma , Humanos , Metaloproteinase 2 da Matriz , Acetogeninas/farmacologia , Necroptose , Glioblastoma/metabolismo , Temozolomida/farmacologia , Linhagem Celular Tumoral , Neoplasias Encefálicas/tratamento farmacológico , Neoplasias Encefálicas/patologia , Resistencia a Medicamentos Antineoplásicos , Apoptose
2.
Angew Chem Int Ed Engl ; 62(8): e202214830, 2023 Feb 13.
Artigo em Inglês | MEDLINE | ID: mdl-36469860

RESUMO

Electrochemically converting nitrate to ammonia is an essential and sustainable approach to restoring the globally perturbed nitrogen cycle. The rational design of catalysts for the nitrate reduction reaction (NO3 RR) based on a detailed understanding of the reaction mechanism is of high significance. We report a Cu2 O+Co3 O4 tandem catalyst which enhances the NH3 production rate by ≈2.7-fold compared to Co3 O4 and ≈7.5-fold compared with Cu2 O, respectively, however, most importantly, we precisely place single Cu2 O and Co3 O4 cube-shaped nanoparticles individually and together on carbon nanoelectrodes provide insight into the mechanism of the tandem catalysis. The structural and phase evolution of the individual Cu2 O+Co3 O4 nanocubes during NO3 RR is unveiled using identical location transmission electron microscopy. Combining single-entity electrochemistry with precise nano-placement sheds light on the dynamic transformation of single catalyst particles during tandem catalysis in a direct way.

3.
Chemistry ; 28(12): e202104249, 2022 Feb 24.
Artigo em Inglês | MEDLINE | ID: mdl-35040207

RESUMO

Bimetallic tandem catalysts have emerged as a promising strategy to locally increase the CO flux during electrochemical CO2 reduction, so as to maximize the rate of conversion to C-C-coupled products. Considering this, a novel Cu/C-Ag nanostructured catalyst has been prepared by a redox replacement process, in which the ratio of the two metals can be tuned by the replacement time. An optimum Cu/Ag composition with similarly sized particles showed the highest CO2 conversion to C2+ products compared to non-Ag-modified gas-diffusion electrodes. Gas chromatography and in-situ Raman measurements in a CO2 gas diffusion cell suggest the formation of top-bound linear adsorbed *CO followed by consumption of CO in the successive cascade steps, as evidenced by the increasingνC-H bands. These findings suggest that two mechanisms operate simultaneously towards the production of HCO2 H and C-C-coupled products on the Cu/Ag bimetallic surface.

4.
Chemistry ; 27(19): 5906-5912, 2021 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-33527522

RESUMO

Discerning the influence of electrochemical reactions on the electrode microenvironment is an unavoidable topic for electrochemical reactions that involve the production of OH- and the consumption of water. That is particularly true for the carbon dioxide reduction reaction (CO2 RR), which together with the competing hydrogen evolution reaction (HER) exert changes in the local OH- and H2 O activity that in turn can possibly affect activity, stability, and selectivity of the CO2 RR. We determine the local OH- and H2 O activity in close proximity to a CO2 -converting Ag-based gas diffusion electrode (GDE) with product analysis using gas chromatography. A Pt nanosensor is positioned in the vicinity of the working GDE using shear-force-based scanning electrochemical microscopy (SECM) approach curves, which allows monitoring changes invoked by reactions proceeding within an otherwise inaccessible porous GDE by potentiodynamic measurements at the Pt-tip nanosensor. We show that high turnover HER/CO2 RR at a GDE lead to modulations of the alkalinity of the local electrolyte, that resemble a 16 m KOH solution, variations that are in turn linked to the reaction selectivity.

5.
Angew Chem Int Ed Engl ; 60(16): 9135-9141, 2021 Apr 12.
Artigo em Inglês | MEDLINE | ID: mdl-33559233

RESUMO

Electroreduction of CO2 to multi-carbon products has attracted considerable attention as it provides an avenue to high-density renewable energy storage. However, the selectivity and stability under high current densities are rarely reported. Herein, B-doped Cu (B-Cu) and B-Cu-Zn gas diffusion electrodes (GDE) were developed for highly selective and stable CO2 conversion to C2+  products at industrially relevant current densities. The B-Cu GDE exhibited a high Faradaic efficiency of 79 % for C2+  products formation at a current density of -200 mA cm-2 and a potential of -0.45 V vs. RHE. The long-term stability for C2+ formation was substantially improved by incorporating an optimal amount of Zn. Operando Raman spectra confirm the retained Cu+ species under CO2 reduction conditions and the lower overpotential for *OCO formation upon incorporation of Zn, which lead to the excellent conversion of CO2 to C2+ products on B-Cu-Zn GDEs.

6.
Angew Chem Int Ed Engl ; 60(43): 23427-23434, 2021 Oct 18.
Artigo em Inglês | MEDLINE | ID: mdl-34355835

RESUMO

Developing highly efficient and selective electrocatalysts for the CO2 reduction reaction to produce value-added chemicals has been intensively pursued. We report a series of Cux Oy Cz nanostructured electrocatalysts derived from a Cu-based MOF as porous self-sacrificial template. Blending catalysts with polytetrafluoroethylene (PTFE) on gas diffusion electrodes (GDEs) suppressed the competitive hydrogen evolution reaction. 25 to 50 wt % teflonized GDEs exhibited a Faradaic efficiency of ≈54 % for C2+ products at -80 mA cm-2 . The local OH- ions activity of PTFE-modified GDEs was assessed by means of closely positioning a Pt-nanoelectrode. A substantial increase in the OH- /H2 O activity ratio due to the locally generated OH- ions at increasing current densities was determined irrespective of the PTFE amount.

7.
Angew Chem Int Ed Engl ; 60(4): 2000-2006, 2021 01 25.
Artigo em Inglês | MEDLINE | ID: mdl-33075190

RESUMO

Well-defined assemblies of photosynthetic protein complexes are required for an optimal performance of semi-artificial energy conversion devices, capable of providing unidirectional electron flow when light-harvesting proteins are interfaced with electrode surfaces. We present mixed photosystem I (PSI) monolayers constituted of native cyanobacterial PSI trimers in combination with isolated PSI monomers from the same organism. The resulting compact arrangement ensures a high density of photoactive protein complexes per unit area, providing the basis to effectively minimize short-circuiting processes that typically limit the performance of PSI-based bioelectrodes. The PSI film is further interfaced with redox polymers for optimal electron transfer, enabling highly efficient light-induced photocurrent generation. Coupling of the photocathode with a [NiFeSe]-hydrogenase confirms the possibility to realize light-induced H2 evolution.


Assuntos
Técnicas Eletroquímicas/instrumentação , Complexo de Proteína do Fotossistema I/metabolismo , Anisotropia , Cianobactérias/metabolismo , Transporte de Elétrons , Luz
8.
J Chem Phys ; 153(1): 014707, 2020 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-32640827

RESUMO

Thin-film material libraries in the ternary and quaternary metal oxide systems Fe-V-O, Cu-V-O, and Cu-Fe-V-O were synthesized using combinatorial reactive co-sputtering with subsequent annealing in air. Their compositional, structural, and functional properties were assessed using high-throughput characterization methods. Prior to the investigation of the quaternary system Cu-Fe-V-O, the compositions (Fe61V39)Ox and (Cu52V48)Ox with promising photoactivity were identified from their ternary subsystems Fe-V-O and Cu-V-O, respectively. Two Cu-Fe-V-O material libraries with (Cu29-72Fe4-27V22-57)Ox and (Cu11-55Fe27-73V12-34)Ox composition spread were investigated. Seven mixed ternary and quaternary phase regions were identified: I (α-Cu3FeV6O26/FeVO4), II (Cu5V2O10/FeVO4/α-Cu3Fe4V6O26), III (Cu5V2O10), IV (Cu5V2O10/FeVO4, V (FeVO4/γ-Cu2V2O7/α-Cu3Fe4V6O26), VI (ß-Cu2V2O7/α-Cu3Fe4V6O26/FeVO4), and VII (ß-Cu3Fe4V6O26/FeVO4). In the investigated composition range, two photoactive regions, (Cu53Fe7V40)Ox and (Cu45Fe21V34)Ox, were identified, exhibiting 103 µA/cm2 and 108 µA/cm2 photocurrent density for the oxygen evolution reaction at 1.63 V vs reversible hydrogen electrode, respectively. The highest photoactive region (Cu45Fe21V34)Ox comprises the dominant α-Cu3Fe4V6O24 phase and minor FeVO4 phase. This photoactive region corresponds to having an indirect bandgap of 1.87 eV and a direct bandgap of 2.58 eV with an incident photon-to-current efficiency of 30% at a wavelength of 310 nm.

9.
Chem Biodivers ; 17(11): e2000484, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32960490

RESUMO

Our search for candidates for photosynthesis inhibitors is allowing us to report the effect of two acetogenins identified in Annona coriacea Mart. leaves, ACG-A and ACG-B, a non-adjacent bis-THF and a mono-THF types, respectively. This is an important class of natural products which presents biological properties such as anticancer, neurotoxic, larvicidal and insecticidal. However, this is only the second report associated to its herbicidal activity. Their mechanisms of action on the light reactions of the photosynthesis were elucidated by polarographic techniques. Compounds inhibited the noncyclic electron transport on basal, phosphorylating, and uncoupled conditions from H2 O to methyl viologen (MV); therefore, they act as Hill reaction inhibitors. Studies on fluorescence of chlorophyll a (ChL a) indicated that they inhibited the acceptor side of PSII between P680 and PQ-pool, exactly as the commercial herbicide DCMU does.


Assuntos
Acetogeninas/química , Annona/química , Acetogeninas/isolamento & purificação , Acetogeninas/metabolismo , Acetogeninas/farmacologia , Annona/metabolismo , Clorofila A/química , Cloroplastos/metabolismo , Transporte de Elétrons/efeitos dos fármacos , Luz , Fotossíntese/efeitos dos fármacos , Fotossíntese/efeitos da radiação , Complexo de Proteína do Fotossistema II/antagonistas & inibidores , Complexo de Proteína do Fotossistema II/metabolismo , Folhas de Planta/química , Folhas de Planta/metabolismo , Spinacia oleracea/metabolismo
10.
Molecules ; 24(21)2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31683835

RESUMO

Plant-based compounds are an option to explore and perhaps overcome the limitations of current antitumor treatments. Annona coriacea Mart. is a plant with a broad spectrum of biological activities, but its antitumor activity is still unclear. The purpose of our study was to determine the effects of A. coriacea fractions on a panel of cervical cancer cell lines and a normal keratinocyte cell line. The antitumor effect was investigated in vitro by viability assays, cell cycle, apoptosis, migration, and invasion assays. Intracellular signaling was assessed by Western blot, and major compounds were identified by mass spectrometry. All fractions exhibited a cytotoxic effect on cisplatin-resistant cell lines, SiHa and HeLa. C3 and C5 were significantly more cytotoxic and selective than cisplatin in SiHa and Hela cells. However, in CaSki, a cisplatin-sensitive cell line, the compounds did not demonstrate higher cytotoxicity when compared with cisplatin. Alkaloids and acetogenins were the main compounds identified in the fractions. These fractions also markedly decreased cell proliferation with p21 increase and cell cycle arrest in G2/M. These effects were accompanied by an increase of H2AX phosphorylation levels and DNA damage index. In addition, fractions C3 and C5 promoted p62 accumulation and decrease of LC3II, as well as acid vesicle levels, indicating the inhibition of autophagic flow. These findings suggest that A. coriacea fractions may become effective antineoplastic drugs and highlight the autophagy inhibition properties of these fractions in sensitizing cervical cancer cells to treatment.


Assuntos
Annona/química , Proliferação de Células/efeitos dos fármacos , Extratos Vegetais/farmacologia , Neoplasias do Colo do Útero/tratamento farmacológico , Apoptose/efeitos dos fármacos , Autofagia/efeitos dos fármacos , Pontos de Checagem do Ciclo Celular/efeitos dos fármacos , Cisplatino/efeitos adversos , Cisplatino/farmacologia , Resistencia a Medicamentos Antineoplásicos/efeitos dos fármacos , Feminino , Células HeLa , Humanos , Extratos Vegetais/química , Transdução de Sinais/efeitos dos fármacos
11.
Langmuir ; 34(41): 12293-12301, 2018 10 16.
Artigo em Inglês | MEDLINE | ID: mdl-30247044

RESUMO

Surface-enhanced Raman spectroscopy is a powerful analytical tool and a strongly surface structure-dependent process. Importantly, it can be coupled with electrochemistry to simultaneously record vibrational spectroscopic information during electrocatalytic reactions. Highest Raman enhancements are obtained using precisely tuned nanostructures. The fabrication and evaluation of a high number of different nanostructures with slightly different properties is time-consuming. We present a strategy to systematically determine optimal nanostructure properties of electrochemically generated Ag void structures in order to find the void size providing highest signal enhancement for Raman spectroscopy. Ag-coated Si wafers were decorated with a monolayer of differently sized polymer nanospheres using a Langmuir-Blodgett approach. Subsequently, bipolar electrochemistry was used to electrodeposit a gradient of differently sized void structures. The gradient structures were locally evaluated using Raman spectroscopy of a surface-adsorbed Raman probe, and the surface regions exhibiting the highest Raman enhancement were characterized by means of scanning electron microscopy. High-throughput scanning droplet cell experiments were utilized to determine suitable conditions for the electrodeposition of the found highly active structure in a three-electrode electrochemical cell. This structure was subsequently employed as the working electrode in operando surface-enhanced Raman measurements to verify its viability as the signal amplifier and to spectroscopically rationalize the complex electrochemical reduction of carbon dioxide.

12.
Dermatol Surg ; 42(2): 183-90, 2016 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-26845538

RESUMO

BACKGROUND: Racial melanonychia striata is a nail plate dyschromia described as a gray coloration of the background in dermatoscopy and hypermelanosis in histology. However, many cases with brown or black coloration of the background in the dermatoscopic examination have been followed. OBJECTIVE: Evaluate racial melanonychia striata dermatoscopical patterns and histological diagnosis in Fitzpatrick skin Types IV, V, or VI population. MATERIALS AND METHODS: 482 Fitzpatrick skin Types IV, V, or VI patients, between 19 and 72 years of age, were clinically evaluated and underwent nail plate dermatoscopic examination. Fifty-eight patients presenting melanonychia striata and dermatoscopic patterns with brown or black coloration of the background were submitted to a nail matrix biopsy. When occurring in more than 1 digit, biopsy was performed in the lesion with the darkest coloration presented in dermatoscopy. RESULTS: All skin Types IV, V, or VI patients who had melanonychia striata, with brown or black coloration of the background in the dermatoscopic examination, revealed histopathological analysis compatible with hypermelanosis. CONCLUSION: Racial melanonychia in skin Types IV, V, or VI patients, resulting from hypermelanosis, may present brown or black coloration of the background in the dermatoscopic examination.


Assuntos
Doenças da Unha/etnologia , Doenças da Unha/patologia , Transtornos da Pigmentação/etnologia , Transtornos da Pigmentação/patologia , Adolescente , Adulto , Idoso , Biópsia , Dermoscopia , Diagnóstico Diferencial , Feminino , Humanos , Masculino , Melanoma/patologia , Pessoa de Meia-Idade , Neoplasias Cutâneas/patologia , Adulto Jovem
13.
Nat Commun ; 15(1): 8583, 2024 Oct 03.
Artigo em Inglês | MEDLINE | ID: mdl-39362855

RESUMO

The electroreduction of nitrate offers a promising, sustainable, and decentralized route to generate valuable ammonia. However, a key challenge in the nitrate reduction reaction is the energy efficiency of the reaction, which requires both a high ammonia yield rate and a high Faradaic efficiency of ammonia at a low working potential (≥-0.2 V versus reversible hydrogen electrode). We propose a bimetallic Co-B/Ru12 electrocatalyst which utilizes complementary effects of Co-B and Ru to modulate the quantity of adsorbed hydrogen and to favor the specific hydrogenation for initiating nitrate reduction reaction at a low overpotential. This effect enables the catalyst to achieve a Faradaic efficiency for ammonia of 90.4 ± 9.2% and a remarkable half-cell energy efficiency of 40.9 ± 4% at 0 V versus reversible hydrogen electrode. The in-situ electrochemical reconstruction of the catalyst contributes to boosting the ammonia yield rate to a high level of 15.0 ± 0.7 mg h-1 cm-2 at -0.2 V versus reversible hydrogen electrode. More importantly, by employing single-entity electrochemistry coupled with identical location transmission electron microscopy, we gain systematic insights into the correlation between the increase in the catalyst's active sites and its structural transformations during the nitrate reduction reaction.

14.
Adv Mater ; 35(32): e2303050, 2023 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-37235856

RESUMO

Renewable electricity-powered nitrate (NO3 - ) reduction reaction (NO3 RR) offers a net-zero carbon route to the realization of high ammonia (NH3 ) productivity. However, this route suffers from low energy efficiency (EE, with a half-cell EE commonly <36%), since high overpotentials are required to overcome the weak NO3 - binding affinity and sluggish NO3 RR kinetics. To alleviate this, a rational catalyst design strategy that involves the linear assembly of sub-5 nm Cu/Co nanophases into sub-20 nm thick nanoribbons is suggested. The theoretical and experimental studies show that the Cu-Co nanoribbons, similar to enzymes, enable strong NO3 - adsorption and rapid tandem catalysis of NO3 - to NH3 , owing to their richly exposed binary phase boundaries and adjacent Cu-Co sites at sub-5 nm distance. In situ Raman spectroscopy further reveals that at low applied overpotentials, the Cu/Co nanophases are rapidly activated and subsequently stabilized by a specifically designed redox polymer that in situ scavenges intermediately formed highly oxidative nitrogen dioxide (NO2 ). As a result, a stable NO3 RR with a current density of ≈450 mA cm-2 is achieved, a Faradaic efficiency of >97% for the formation of NH3 , and an unprecedented half-cell EE of ≈42%.

15.
Chem Asian J ; 18(2): e202201165, 2023 Jan 17.
Artigo em Inglês | MEDLINE | ID: mdl-36445811

RESUMO

Bi-based electrocatalysts have been widely investigated in the CO2 reduction reaction (CO2 RR) for the formation of formate. However, it remains a challenge to achieve high Faradaic efficiency (FE) and industrial current densities at low overpotentials for obtaining both high formate productivity and energy efficiency (EE). Herein, we report an Ag-Bi2 O3 hybrid nanofiber (Ag-Bi2 O3 ) for highly efficient electrochemical reduction of CO2 to formate. Ag-Bi2 O3 exhibits a formate FE of >90% for current densities from -10 to -250 mA ⋅ cm-2 and attains a yield rate of 11.7 mmol ⋅ s-1 ⋅ m-2 at -250 mA ⋅ cm-2 . Moreover, Ag-Bi2 O3 increased the EE (52.7%) by nearly 10% compared to a Bi2 O3 only counterpart. Structural characterization and in-situ Raman results suggest that the presence of Ag induced the conversion of Bi2 O3 from a monoclinic phase (α-Bi2 O3 ) to a metastable tetragonal phase (ß-Bi2 O3 ) and accelerated the formation of active metallic Bi at low overpotentials (at > -0.3 V), which together contributes to the highly efficient formate formation.

16.
ChemSusChem ; 16(11): e202202349, 2023 Jun 09.
Artigo em Inglês | MEDLINE | ID: mdl-36897020

RESUMO

Electrochemical CO2 conversion is a key technology to promote the production of carbon-containing molecules, alongside reducing CO2 emissions leading to a closed carbon cycle economy. Over the past decade, the interest to develop selective and active electrochemical devices for electrochemical CO2 reduction emerged. However, most reports employ oxygen evolution reaction as an anodic half-cell reaction causing the system to suffer from sluggish kinetics with no production of value-added chemicals. Therefore, this study reports a conceptualized paired electrolyzer for simultaneous anodic and cathodic formate production at high currents. To achieve this, CO2 reduction was coupled with glycerol oxidation: a BiOBr-modified gas-diffusion cathode and a Nix B on Ni foam anode keep their selectivity for formate in the paired electrolyzer compared to the half-cell measurements. The paired reactor here reaches a combined Faradaic efficiency for formate of 141 % (45 % anode and 96 % cathode) at a current density of 200 mA cm-2 .


Assuntos
Dióxido de Carbono , Glicerol , Eletrodos , Formiatos
17.
ChemElectroChem ; 9(21): e202200675, 2022 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-36636096

RESUMO

Gas diffusion electrodes (GDEs) in CO2 reduction reaction (CO2RR) alleviate the mass transfer limitation of gaseous reagents, which is beneficial for reducing CO2 into valuable chemicals. GDEs offer higher current densities compared to electrodes immersed in the electrolyte. Disclosing the roles of different structural parameters in tuning the performance of the GDEs is essential to exert the potential of catalysts and to meet potential large-scale industrial applications of the CO2RR. A novel layer structure for the airbrush-type spray fabrication of GDEs was designed and optimised, comprising a carbon-based gas-diffusion layer, a PEEK fabric, a Ni mesh, a carbon-integrated catalyst layer, and a PTFE top layer. It was shown that adjusting the carbon material in the gas diffusion and the catalyst layer impacts the selectivity of the CO2RR due to the modulation of the pore network. This work disclosed a practical and scalable but also an easily transferable pathway for preparing GDEs and offered an idea of how to tune the significant parameters of GDEs for optimising their CO2RR performance.

18.
Nat Commun ; 13(1): 1129, 2022 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-35236840

RESUMO

Electrocatalytic recycling of waste nitrate (NO3-) to valuable ammonia (NH3) at ambient conditions is a green and appealing alternative to the Haber-Bosch process. However, the reaction requires multi-step electron and proton transfer, making it a grand challenge to drive high-rate NH3 synthesis in an energy-efficient way. Herein, we present a design concept of tandem catalysts, which involves coupling intermediate phases of different transition metals, existing at low applied overpotentials, as cooperative active sites that enable cascade NO3--to-NH3 conversion, in turn avoiding the generally encountered scaling relations. We implement the concept by electrochemical transformation of Cu-Co binary sulfides into potential-dependent core-shell Cu/CuOx and Co/CoO phases. Electrochemical evaluation, kinetic studies, and in-situ Raman spectra reveal that the inner Cu/CuOx phases preferentially catalyze NO3- reduction to NO2-, which is rapidly reduced to NH3 at the nearby Co/CoO shell. This unique tandem catalyst system leads to a NO3--to-NH3 Faradaic efficiency of 93.3 ± 2.1% in a wide range of NO3- concentrations at pH 13, a high NH3 yield rate of 1.17 mmol cm-2 h-1 in 0.1 M NO3- at -0.175 V vs. RHE, and a half-cell energy efficiency of ~36%, surpassing most previous reports.

19.
ACS Appl Mater Interfaces ; 14(41): 46421-46426, 2022 Oct 19.
Artigo em Inglês | MEDLINE | ID: mdl-36194638

RESUMO

The development of electrodes for efficient CO2 reduction while forming valuable compounds is critical. The use of enzymes as catalysts provides the advantage of high catalytic activity in combination with highly selective transformations. We describe the electrical wiring of a carbon monoxide dehydrogenase II from Carboxydothermus hydrogenoformans (ChCODH II) using a cobaltocene-based low-potential redox polymer for the selective reduction of CO2 to CO over gas diffusion electrodes. High catalytic current densities of up to -5.5 mA cm-2 are achieved, exceeding the performance of previously reported bioelectrodes for CO2 reduction based on either carbon monoxide dehydrogenases or formate dehydrogenases. The proposed bioelectrode reveals considerable stability with a half-life of more than 20 h of continuous operation. Product quantification using gas chromatography confirmed the selective transformation of CO2 into CO without any parasitic co-reactions at the applied potentials.


Assuntos
Monóxido de Carbono , Formiato Desidrogenases , Formiato Desidrogenases/química , Monóxido de Carbono/química , Dióxido de Carbono/química , Polímeros , Instalação Elétrica , Eletrodos , Oxirredução
20.
Adv Mater ; 34(13): e2109108, 2022 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-35062041

RESUMO

The number of active sites and their intrinsic activity are key factors in designing high-performance catalysts for the oxygen evolution reaction (OER). The synthesis, properties, and in-depth characterization of a homogeneous CoNiFeCu catalyst are reported, demonstrating that multimetal synergistic effects improve the OER kinetics and the intrinsic activity. In situ carbon corrosion and Cu leaching during the OER lead to an enhanced electrochemically active surface area, providing favorable conditions for improved electronic interaction between the constituent metals. After activation, the catalyst exhibits excellent activity with a low overpotential of 291.5 ± 0.5 mV at 10 mA cm-2 and a Tafel slope of 43.9 mV dec-1 . It shows superior stability compared to RuO2 in 1 m KOH, which is even preserved for 120 h at 500 mA cm-2 in 7 m KOH at 50 °C. Single particles of this CoNiFeCu after their placement on nanoelectrodes combined with identical location transmission electron microscopy before and after applying cyclic voltammetry are investigated. The improved catalytic performance is due to surface carbon corrosion and Cu leaching. The proposed catalyst design strategy combined with the unique single-nanoparticle technique contributes to the development and characterization of high-performance catalysts for electrochemical energy conversion.

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