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2.
Kaohsiung J Med Sci ; 40(5): 467-476, 2024 May.
Article in English | MEDLINE | ID: mdl-38523603

ABSTRACT

Combining epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) with an anti- vascular endothelial growth factor (VEGF) agent, bevacizumab or ramucirumab, is indicated for advanced lung adenocarcinoma harboring EGFR mutation. This study aimed to show the real-world data of combination therapy and compare the effectiveness between bevacizumab and ramucirumab in combination with an EGFR-TKI. This retrospective study enrolled 47 patients diagnosed of stage IV lung adenocarcinoma with exon 19 deletion or L858R point mutation, receiving a first-line EGFR-TKI with anti-VEGF agent, including 34 (72%) and 13 (28%) patients receiving bevacizumab and ramucirumab, respectively. The response rate was similar in both groups (p = 0.38). Patients receiving bevacizumab had similar progression free survival (PFS) as those receiving ramucirumab (median PFS: 21.9 vs. 24.2 months, p = 0.4871); similar finding was noted in overall survival (OS) (median OS: 33.5 months vs. not reached, p = 0.4618). Patients receiving ramucirumab experienced a significantly high-grade hypertension compared to those receiving bevacizumab (p = 0.0351). Multivariable Cox regression analysis found independent risk factors for worse PFS included poorer ECOG performance status, multiple (≥3) metastatic sites, brain metastasis, and pleural metastasis/effusion, while the type of anti-VEGF agent was not a risk factor. Pericardial metastasis/effusion was the only one independent risk factor for worse OS. In summary, ramucirumab may have similar effectiveness as bevacizumab in combination with an EGFR-TKI as first line therapy for advanced lung adenocarcinoma harboring susceptible EGFR mutation. Further large-scale registry-based cohort studies may be needed to validate our findings.


Subject(s)
Antibodies, Monoclonal, Humanized , Bevacizumab , Carcinoma, Non-Small-Cell Lung , ErbB Receptors , Lung Neoplasms , Mutation , Protein Kinase Inhibitors , Ramucirumab , Humans , Male , Female , ErbB Receptors/genetics , ErbB Receptors/antagonists & inhibitors , Bevacizumab/therapeutic use , Bevacizumab/administration & dosage , Antibodies, Monoclonal, Humanized/therapeutic use , Middle Aged , Aged , Carcinoma, Non-Small-Cell Lung/drug therapy , Carcinoma, Non-Small-Cell Lung/genetics , Carcinoma, Non-Small-Cell Lung/pathology , Lung Neoplasms/drug therapy , Lung Neoplasms/genetics , Lung Neoplasms/pathology , Protein Kinase Inhibitors/therapeutic use , Antineoplastic Combined Chemotherapy Protocols/therapeutic use , Treatment Outcome , Adult , Retrospective Studies , Aged, 80 and over , Neoplasm Staging , Adenocarcinoma of Lung/drug therapy , Adenocarcinoma of Lung/genetics , Adenocarcinoma of Lung/pathology
3.
ACS Catal ; 13(11): 7488-7498, 2023 Jun 02.
Article in English | MEDLINE | ID: mdl-37288096

ABSTRACT

In the search for rational design strategies for oxygen evolution reaction (OER) catalysts, linking the catalyst structure to activity and stability is key. However, highly active catalysts such as IrOx and RuOx undergo structural changes under OER conditions, and hence, structure-activity-stability relationships need to take into account the operando structure of the catalyst. Under the highly anodic conditions of the oxygen evolution reaction (OER), electrocatalysts are often converted into an active form. Here, we studied this activation for amorphous and crystalline ruthenium oxide using X-ray absorption spectroscopy (XAS) and electrochemical scanning electron microscopy (EC-SEM). We tracked the evolution of surface oxygen species in ruthenium oxides while in parallel mapping the oxidation state of the Ru atoms to draw a complete picture of the oxidation events that lead to the OER active structure. Our data show that a large fraction of the OH groups in the oxide are deprotonated under OER conditions, leading to a highly oxidized active material. The oxidation is centered not only on the Ru atoms but also on the oxygen lattice. This oxygen lattice activation is particularly strong for amorphous RuOx. We propose that this property is key for the high activity and low stability observed for amorphous ruthenium oxide.

4.
ACS Appl Mater Interfaces ; 15(25): 30052-30059, 2023 Jun 28.
Article in English | MEDLINE | ID: mdl-37318204

ABSTRACT

Catalyst degradation and product selectivity changes are two of the key challenges in the electrochemical reduction of CO2 on copper electrodes. Yet, these aspects are often overlooked. Here, we combine in situ X-ray spectroscopy, in situ electron microscopy, and ex situ characterization techniques to follow the long-term evolution of the catalyst morphology, electronic structure, surface composition, activity, and product selectivity of Cu nanosized crystals during the CO2 reduction reaction. We found no changes in the electronic structure of the electrode under cathodic potentiostatic control over time, nor was there any build-up of contaminants. In contrast, the electrode morphology is modified by prolonged CO2 electroreduction, which transforms the initially faceted Cu particles into a rough/rounded structure. In conjunction with these morphological changes, the current increases and the selectivity changes from value-added hydrocarbons to less valuable side reaction products, i.e., hydrogen and CO. Hence, our results suggest that the stabilization of a faceted Cu morphology is pivotal for ensuring optimal long-term performance in the selective reduction of CO2 into hydrocarbons and oxygenated products.

5.
Nat Nanotechnol ; 18(7): 763-771, 2023 Jul.
Article in English | MEDLINE | ID: mdl-37231143

ABSTRACT

Heterogeneous single-atom spin catalysts combined with magnetic fields provide a powerful means for accelerating chemical reactions with enhanced metal utilization and reaction efficiency. However, designing these catalysts remains challenging due to the need for a high density of atomically dispersed active sites with a short-range quantum spin exchange interaction and long-range ferromagnetic ordering. Here, we devised a scalable hydrothermal approach involving an operando acidic environment for synthesizing various single-atom spin catalysts with widely tunable substitutional magnetic atoms (M1) in a MoS2 host. Among all the M1/MoS2 species, Ni1/MoS2 adopts a distorted tetragonal structure that prompts both ferromagnetic coupling to nearby S atoms as well as adjacent Ni1 sites, resulting in global room-temperature ferromagnetism. Such coupling benefits spin-selective charge transfer in oxygen evolution reactions to produce triplet O2. Furthermore, a mild magnetic field of ~0.5 T enhances the oxygen evolution reaction magnetocurrent by ~2,880% over Ni1/MoS2, leading to excellent activity and stability in both seawater and pure water splitting cells. As supported by operando characterizations and theoretical calculations, a great magnetic-field-enhanced oxygen evolution reaction performance over Ni1/MoS2 is attributed to a field-induced spin alignment and spin density optimization over S active sites arising from field-regulated S(p)-Ni(d) hybridization, which in turn optimizes the adsorption energies for radical intermediates to reduce overall reaction barriers.

6.
J Formos Med Assoc ; 122(10): 1061-1068, 2023 Oct.
Article in English | MEDLINE | ID: mdl-37105870

ABSTRACT

BACKGROUND/PURPOSE: Pulmonary alveolar proteinosis (PAP) is rare disease manifested as alveolar macrophage dysfunction and abnormal accumulation of surfactant protein in the alveoli. In this nationwide, population-based study, we investigated the epidemiology of PAP in Taiwan, and discovered the comorbidities and prognostic factors of PAP. METHODS: From the National Health Insurance Research Database (NHIRD), we obtained comprehensive information about all patients of PAP in Taiwan between 1995 and 2013. The incidence, baseline characteristics comorbidities, and prognostic factors of PAP were investigated. RESULTS: The annual incidence rate of PAP was around 0.79 (range: 0.49-1.17) patients per million people after 2000, and the prevalence rate was 7.96 patients per million people by the end of 2013. In total, 276 patients of PAP were identified, including 177 (64%) and 99 (36%) patients with primary and secondary PAP, respectively. The median age of diagnosis was 53.8 years. The median survival was 9.6 years after the initial PAP diagnosis, and the 5-year survival rate was 65.96%. Twenty (7%) patients received whole lung lavage (WLL) within three months after the diagnosis had significantly better survival compared to the others. Multivariable Cox regression analyses showed that elder age, secondary PAP, and malignancy were associated with poorer survival, while WLL within 3 months of diagnosis might greatly improve the survival. CONCLUSION: We demonstrated the epidemiology of PAP in Taiwan, showing several poor prognostic factors and the potential effectiveness of WLL. Further prospective studies based on registry are warranted to improve the diagnosis and treatment of PAP.


Subject(s)
Pulmonary Alveolar Proteinosis , Humans , Aged , Middle Aged , Infant , Pulmonary Alveolar Proteinosis/epidemiology , Pulmonary Alveolar Proteinosis/therapy , Pulmonary Alveolar Proteinosis/diagnosis , Taiwan/epidemiology , Prospective Studies , Bronchoalveolar Lavage , Lung/pathology
7.
Cancers (Basel) ; 15(7)2023 Mar 28.
Article in English | MEDLINE | ID: mdl-37046679

ABSTRACT

Afatinib is an irreversible tyrosine kinase inhibitor (TKI) targeting the epidermal growth factor receptor (EGFR), which is utilized for the treatment of patients with advanced lung cancer that harbors EGFR mutations. No studies have evaluated the clinical efficacy of LCT in patients treated with first-line afatinib. In this study, we retrospectively enrolled patients with advanced lung adenocarcinomas harboring susceptible EGFR mutations who were diagnosed and treated with first-line afatinib in three hospitals. A total of 254 patients were enrolled, including 30 (12%) patients who received LCT (15 patients received definitive radiotherapy for the primary lung mass and 15 patients received curative surgery). Patients who received LCT had a significantly longer PFS than those who did not (median PFS: 32.8 vs. 14.5 months, p = 0.0008). Patients who received LCT had significantly longer OS than those who did not (median OS: 67.1 vs. 34.5 months, p = 0.0011). Multivariable analysis showed LCT was an independent prognostic factor for improved PFS (adjusted hazard ratio [aHR] [95% confidence interval (CI)]: 0.44 [0.26-0.73], p = 0.0016) and OS (aHR [95% CI]: 0.26 [0.12-0.54], p = 0.0004). The analyses using propensity score-weighting showed consistent results. We conclude that LCT may improve clinical outcomes, in terms of PFS and OS, in patients with advanced EGFR-mutant lung adenocarcinomas who are treated with first-line afatinib.

8.
J Oncol Pharm Pract ; 29(6): 1374-1380, 2023 Sep.
Article in English | MEDLINE | ID: mdl-36112905

ABSTRACT

BACKGROUND: Painful paronychia and pseudopyogenic granuloma (PG) are common adverse drug reactions (ADRs) associated with the use of epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) to treat non-small cell lung cancer (NSCLC). Multiple local management approaches have been tested with unsatisfactory results. We have introduced an occlusion therapy technique through which available topical drugs for longer than 2 years. METHODS: Based on the cancer registry and case management system of our hospital, from July 2019 to July 2020, we retrospectively enrolled patients with NSCLC who were treated with EGFR-TKIs and received applications of 0.5% timolol ophthalmic solution (TIMOPTOL XE 0.5%®) combined with a neomycin/tyrothricin ointment (Biomycin®) using the occlusion method to treat paronychia or PG. RESULTS: A total of 22 patients were enrolled, with a mean age of 66.5 years, most of whom were women (72.7%). Periungual lesion-related pain was reported by all patients, and periungual bleeding and PG were reported in 14% (3/22) and 64% (14/22) of patients, respectively. After the occlusion therapy application of timolol ophthalmic solution combined with neomycin/tyrothricin ointment twice daily, the overall response rate was 83.3%, including complete response in 18% (4/22) of cases and partial response in 68% (15/22) of cases. CONCLUSION: We presented an occlusion method using available topical beta-blockers and antibiotic ointment for EGFR-TKI-induced paronychia and PG in Taiwan. The result is favorable. Further randomized control trial is urgent to validate our findings.


Subject(s)
Angiolymphoid Hyperplasia with Eosinophilia , Carcinoma, Non-Small-Cell Lung , Lung Neoplasms , Paronychia , Humans , Female , Aged , Male , Carcinoma, Non-Small-Cell Lung/drug therapy , Lung Neoplasms/drug therapy , Timolol/adverse effects , Angiolymphoid Hyperplasia with Eosinophilia/chemically induced , Angiolymphoid Hyperplasia with Eosinophilia/drug therapy , Retrospective Studies , Anti-Bacterial Agents/adverse effects , Paronychia/chemically induced , Paronychia/drug therapy , Ointments/adverse effects , Taiwan , Protein Kinase Inhibitors/adverse effects , Neomycin/adverse effects , ErbB Receptors , Tyrothricin/adverse effects , Ophthalmic Solutions/adverse effects , Mutation
9.
Biomedicines ; 10(8)2022 Aug 10.
Article in English | MEDLINE | ID: mdl-36009484

ABSTRACT

Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase overexpressed in various cancer types that plays a critical role in tumor progression. Accumulating evidence suggests that targeting FAK, either alone or in combination with other agents, may serve as an effective therapeutic strategy for numerous cancers. In addition to retarding proliferation, metastasis, and angiogenesis, FAK inhibition triggers cellular senescence in lung cancer cells. However, the detailed mechanism remains enigmatic. In the present study, we found that FAK inhibition not only elicits DNA-damage signaling but also downregulates enhancer of zeste homolog 2 (EZH2) expression. The manipulation of FAK expression influences EZH2 expression and corresponding signaling in vitro. Immunohistochemistry shows that active FAK signaling corresponds with the activation of the EZH2-mediated signaling cascade in lung-cancer-cells-derived tumor tissues. We also found that ectopic EZH2 expression attenuates FAK-inhibition-induced cellular senescence in lung cancer cells. Our results identify EZH2 as a critical downstream effector of the FAK-mediated anti-senescence pathway. Targeting FAK-EZH2 axis-induced cellular senescence may represent a promising therapeutic strategy for restraining tumor growth.

10.
Chest ; 162(2): e85-e88, 2022 08.
Article in English | MEDLINE | ID: mdl-35940668

ABSTRACT

CASE PRESENTATION: A 54-year-old man with chronic hepatitis B was admitted to the hospital with progressive dyspnea on exertion. He reported experiencing intermittent fever, dyspnea on exertion, and relapsing pleuritic chest pain starting 6 months prior, after his first dose of the ChAdOx1 nCoV-19 vaccine. In the past 2 months, he had been admitted to the hospital twice and diagnosed with recurrent pneumonia. Under antibiotic treatment, his dyspnea and low-grade fever demonstrated waxing and waning behaviors. Migratory pulmonary consolidation, which moved from the left lower lobe to the right middle lobe, was identified and diagnosed as relapsing pneumonia. Chest CT scan was performed in a previous admission 2 months earlier that revealed multifocal peripheral consolidation in the left lower lobe and right middle lobe. His occupation required the maintenance of overall fitness, and he denied immunosuppressant use, illicit drug abuse, cigarette smoking, suspicious travel, suspicious contact, or family history. No recent history of trauma, surgery, or air travel was reported.


Subject(s)
ChAdOx1 nCoV-19 , Lung Diseases , Chest Pain/diagnosis , Diagnosis, Differential , Dyspnea/diagnosis , Dyspnea/etiology , Fever/diagnosis , Humans , Lung Diseases/diagnosis , Male , Middle Aged , Tomography, X-Ray Computed
12.
Materials (Basel) ; 15(9)2022 Apr 20.
Article in English | MEDLINE | ID: mdl-35591331

ABSTRACT

This study simulated the after-burned zirconium cladding oxidation in air at temperatures between 500 and 800 °C. The weight changes of Zircaloy-4 cladding with hydrogen contents of 100-1000 ppm continuously measured through thermogravimetric analysis (TGA) during oxidation tests at different temperatures in an air atmosphere. The TGA results indicate a transition of oxidation kinetics from a parabolic rate law to a linear rate law for as-received and hydrided Zircaloy-4 cladding. The hydrogen concentration of Zircaloy-4 had a marked effect on its pre-transition oxidation in air between 500 and 800 °C. For all samples, the linear oxidation (post transition stage) at 650 °C, which is the critical oxidation temperature, displays a similar trend. In addition, scanning electron microscopy and transmission electron micros-copy examinations indicated the presence of a few and numerous discontinuous micro-cracks in the oxide layer in the pre-transition and post-transition stages, respectively.

13.
Small ; 18(18): e2200395, 2022 05.
Article in English | MEDLINE | ID: mdl-35384295

ABSTRACT

Carbon-based single metal atom catalysts (SACs) are being extensively investigated to improve the kinetics of the Li-S redox reaction, which is greatly important for batteries with cell-level energy densities >500 W h kg-1 . However, there are contradictory reports regarding the electrocatalytic activities of the different metal atoms and the role of the metal atom in LiS chemistry still remains unclear. This is due to the complex relationship between the catalytic behavior and the structure of carbon-based SACs. Here, the catalytic behavior and active-site geometry, oxidation state, and the electronic structure of different metal centers (Fe/Co/Ni) embedded in nitrogen-doped graphene, and having similar physicochemical characteristics, are studied. Combining X-ray absorption spectroscopy, density functional theory calculations, and electrochemical analysis, it is revealed that the coordination-geometry and oxidation state of the metal atoms are modified when interacting with sulfur species. This interaction is strongly dependent on the hybridization of metal 3d and S p-orbitals. A moderate hybridization with the Fermi level crossing the metal 3d band is more favorable for LiS redox reactions. This study thus provides a fundamental understanding of how metal atoms in SACs impact LiS redox behavior and offers new guidelines to develop highly active catalytic materials for high-performance LiS batteries.


Subject(s)
Carbon , Metals , Carbon/chemistry , Catalysis , Metals/chemistry , Nitrogen/chemistry , Oxidation-Reduction
15.
Faraday Discuss ; 236(0): 103-125, 2022 Aug 25.
Article in English | MEDLINE | ID: mdl-35485389

ABSTRACT

Photoelectron spectroscopy offers detailed information about the electronic structure and chemical composition of surfaces, owing to the short distance that the photoelectrons can escape from a dense medium. Unfortunately, photoelectron based spectroscopies are not directly compatible with the liquids required to investigate electrochemical processes, especially in the soft X-ray regime. To overcome this issue, different approaches based on photoelectron spectroscopy have been developed in our group over the last few years. The performance and the degree of information provided by these approaches are compared with those of the well established bulk sensitive spectroscopic approach of total fluorescence yield detection, where the surface information gained from this approach is enhanced using samples with large surface to bulk ratios. The operation of these approaches is exemplified and compared using the oxygen evolution reaction on IrOx catalysts. We found that all the approaches, if properly applied, provide similar information about surface oxygen speciation. However, using resonant photoemission spectroscopy, we were able to prove that speciation is more involved and complex than previously thought during the oxygen evolution reaction on IrOx based electrocatalysts. We found that the electrified solid-liquid interface is composed of different oxygen species, where the terminal oxygen atoms on iridium are the active species, yielding the formation of peroxo species and, finally, dioxygen as the reaction product. Thus, the oxygen-oxygen bond formation is dominated by peroxo species formation along the reaction pathway. Furthermore, the methodologies discussed here open up opportunities to investigate electrified solid-liquid interfaces in a multitude of electrochemical processes with unprecedented speciation capabilities, which are not accessible by one-dimensional X-ray spectroscopies.

16.
Int J Mol Sci ; 23(3)2022 Feb 02.
Article in English | MEDLINE | ID: mdl-35163650

ABSTRACT

Focal adhesion kinase (FAK), a non-receptor tyrosine kinase, is overexpressed and activated in many cancer types. FAK regulates diverse cellular processes, including growth factor signaling, cell cycle progression, cell survival, cell motility, angiogenesis, and the establishment of immunosuppressive tumor microenvironments through kinase-dependent and kinase-independent scaffolding functions in the cytoplasm and nucleus. Mounting evidence has indicated that targeting FAK, either alone or in combination with other agents, may represent a promising therapeutic strategy for various cancers. In this review, we summarize the mechanisms underlying FAK-mediated signaling networks during tumor development. We also summarize the recent progress of FAK-targeted small-molecule compounds for anticancer activity from preclinical and clinical evidence.


Subject(s)
Focal Adhesion Kinase 1/physiology , Neoplasms , Animals , Antineoplastic Agents/pharmacology , Humans , Neoplasms/metabolism , Neoplasms/therapy , Tumor Microenvironment
17.
Cancers (Basel) ; 15(1)2022 Dec 28.
Article in English | MEDLINE | ID: mdl-36612183

ABSTRACT

Brain metastasis in patients with non-small-cell lung cancer (NSCLC) harboring epidermal growth factor receptor (EGFR) mutations is a factor of poor prognosis. We conducted a retrospective study to determine the optimal treatment strategy for EGFR-mutant NSCLC patients with brain metastasis receiving or not receiving intracranial intervention. A total of 186 patients treated with an EGFR TKI were enrolled in the study, and 79 (42%) received intracranial intervention. Patients who received intracranial intervention and those who did not had a similar treatment response rate (RR), progression-free survival (PFS) (median PFS: 11.0 vs. 10.0 months, p = 0.4842), and overall survival (OS) (median OS: 23.0 vs. 23.2 months, p = 0.2484). Patients treated with gefitinib, erlotinib, afatinib, or osimertinib had a similar RR (63%, 76%, 81%, or 100%, respectively, p = 0.1390), but they had significantly different PFS (median PFS: 7.5, 10.0, 14.8 months, or not reached, respectively, p = 0.0081). In addition, OS tended to be different between different EGFR TKI treatments (median OS of 19.2, 23.7, or 33.0 months for gefitinib, erlotinib, or afatinib treatments, respectively, p = 0.0834). Afatinib and osimertinib both demonstrated significantly longer PFS than gefitinib in a Cox regression model. Graded prognostic assessment (GPA) versions 2017 and 2022 stratified patients with different OS; patients with higher GPA index scores had significantly longer OS (p = 0.0368 and 0.0407 for version 2017 and 2022, respectively).

18.
J Clin Med ; 10(19)2021 Sep 25.
Article in English | MEDLINE | ID: mdl-34640394

ABSTRACT

Various anaplastic lymphoma kinase inhibitors (ALKIs) have been approved for first-line use in treating anaplastic lymphoma kinase (ALK)-rearranged non-small cell lung cancer (NSCLC). To date, no head-to-head comparison of these newer generation ALKIs has been made, and different efficacies of ALKIs may present across ethnicity. This study aims to compare newer generation ALKIs for treatment efficacy in Asian groups using network meta-analysis. Phase II/III trials that enrolled treatment-naïve Asian ALK-rearranged NSCLC patients treated by ALKIs were included. Progression-free survival (PFS) and overall response rate (ORR) of each trial were extracted as indicators of drug efficacy. Surfaces under cumulative ranking curves (SUCRAs) were calculated as a numeric presentation of the overall ranking associated with each agent. After a systematic literature review, six phase III clinical trials were included. Our results showed that newer generation ALKIs, such as alectinib, brigatinib, ensartinib, and lorlatinib, all demonstrated superior efficacy to crizotinib. Among those, ensartinib exhibited the best overall SUCRA value and ranked first among all agents. According to our network meta-analysis, ensartinib may currently be the most effective first-line treatment for Asian patients with ALK-positive NSCLC. However, this conclusion needs further validation by a larger scale of clinical trials or posthoc analysis of Asian populations. Moreover, in our comparison, low-dose alectinib (300 mg twice daily) exhibited an efficacy profile similar to a higher dose regimen in Asian populations.

19.
Adv Mater ; 33(44): e2101413, 2021 Nov.
Article in English | MEDLINE | ID: mdl-34480499

ABSTRACT

The development of reliable and safe high-energy-density lithium-ion batteries is hindered by the structural instability of cathode materials during cycling, arising as a result of detrimental phase transformations occurring at high operating voltages alongside the loss of active materials induced by transition metal dissolution. Originating from the fundamental structure/function relation of battery materials, the authors purposefully perform crystallographic-site-specific structural engineering on electrode material structure, using the high-voltage LiNi0.5 Mn1.5 O4 (LNMO) cathode as a representative, which directly addresses the root source of structural instability of the Fd 3 ¯ m structure. By employing Sb as a dopant to modify the specific issue-involved 16c and 16d sites simultaneously, the authors successfully transform the detrimental two-phase reaction occurring at high-voltage into a preferential solid-solution reaction and significantly suppress the loss of Mn from the LNMO structure. The modified LNMO material delivers an impressive 99% of its theoretical specific capacity at 1 C, and maintains 87.6% and 72.4% of initial capacity after 1500 and 3000 cycles, respectively. The issue-tracing site-specific structural tailoring demonstrated for this material will facilitate the rapid development of high-energy-density materials for lithium-ion batteries.

20.
J Am Chem Soc ; 143(32): 12524-12534, 2021 Aug 18.
Article in English | MEDLINE | ID: mdl-34355571

ABSTRACT

Iridium and ruthenium and their oxides/hydroxides are the best candidates for the oxygen evolution reaction under harsh acidic conditions owing to the low overpotentials observed for Ru- and Ir-based anodes and the high corrosion resistance of Ir-oxides. Herein, by means of cutting edge operando surface and bulk sensitive X-ray spectroscopy techniques, specifically designed electrode nanofabrication and ab initio DFT calculations, we were able to reveal the electronic structure of the active IrOx centers (i.e., oxidation state) during electrocatalytic oxidation of water in the surface and bulk of high-performance Ir-based catalysts. We found the oxygen evolution reaction is controlled by the formation of empty Ir 5d states in the surface ascribed to the formation of formally IrV species leading to the appearance of electron-deficient oxygen species bound to single iridium atoms (µ1-O and µ1-OH) that are responsible for water activation and oxidation. Oxygen bound to three iridium centers (µ3-O) remains the dominant species in the bulk but do not participate directly in the electrocatalytic reaction, suggesting bulk oxidation is limited. In addition a high coverage of a µ1-OO (peroxo) species during the OER is excluded. Moreover, we provide the first photoelectron spectroscopic evidence in bulk electrolyte that the higher surface-to-bulk ratio in thinner electrodes enhances the material usage involving the precipitation of a significant part of the electrode surface and near-surface active species.

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