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1.
Am J Cancer Res ; 14(5): 1947-1956, 2024.
Article in English | MEDLINE | ID: mdl-38859868

ABSTRACT

Cutaneous melanoma is a prevalent tumor associated with a poor prognosis. This systematic review and meta-analysis aimed to identify and evaluate prognostic factors for patients with cutaneous melanoma following surgery, thereby providing crucial insights for enhancing patient outcomes. We searched PubMed, Embase, Cochrane Library, CINAHL, and Web of Science for studies on postoperative prognostic factors of cutaneous melanoma up to March 2024. Literature screening, data extraction, and quality assessment were performed, followed by meta-analysis using RevMan 5.3 software. Trial Sequential Analysis (TSA) was conducted with Stata 17 software to verify the robustness of the findings. Eleven studies encompassing 27,352 patients were included. The meta-analysis identified several prognostic factors impacting disease-specific survival post-surgery: age over 50 years (HR=1.05, 95% CI: 1.02-1.08), female gender (HR=0.71, 95% CI: 0.57-0.87), Breslow thickness greater than 2 mm (HR=1.11, 95% CI: 1.06-1.17), presence of ulceration (HR=2.06, 95% CI: 1.63-2.60), and positive sentinel lymph node (HR=3.03, 95% CI: 2.50-3.66). TSA confirmed the adequacy of the sample size. Aggressive treatment strategies are recommended for patients exhibiting these characteristics to improve prognosis and extend 5-year survival rates.

2.
Zhongguo Zhong Yao Za Zhi ; 49(9): 2345-2354, 2024 May.
Article in Chinese | MEDLINE | ID: mdl-38812135

ABSTRACT

To investigate the effects of plumbagin on the proliferation and apoptosis of human hepatoma Huh-7 cells and its mechanism based on the creatine kinase B(CKB)/p53 signaling pathway. Huh-7 cells were treated with plumbagin from 1 to 12 µmol·L~(-1) for cell counting kit-8(CCK-8) assay, and 1, 3, and 6 µmol·L~(-1) were determined as low, medium, and high concentrations of plumbagin for subsequent experiments. CKB gene was knocked out in Huh-7 cells by clustered regularly interspaced short palindromic repeats(CRISPR)/CRISPR-associated proteins(Cas)-9 gene editing technology. CKB overexpression lentivirus was transfected into Huh-7 cells to up-regulate the expression of CKB. Cell proliferation and apoptosis were detected by plate cloning assay and flow cytometry. The mRNA expression of CKB was detected by quantitative real-time PCR(qRT-PCR). CKB, p53, mouse double minute 2 homolog(MDM2), B-cell lymphoma 2(Bcl-2), Bcl-2 associated X protein(Bax), and caspase-3 protein were detected by Western blot(WB). The results showed that plumbagin significantly inhibited the proliferation of Huh-7 cells and induced cell apoptosis. Compared with the control group, the apoptosis level was significantly increased in the plumbagin group, while the apoptosis level was significantly decreased in the plumbagin combined with the apoptosis inhibitor group. Plumbagin significantly down-regulated the protein expression levels of CKB, Bcl-2, and MDM2 and up-regulated the protein expression levels of p53, Bax, and caspase-3. Knockdown of the CKB gene decreased the proliferative ability of Huh-7 cells, increased the apoptotic rate, decreased the expression levels of Bcl-2 and MDM2 proteins, and increased the expression levels of p53, Bax, and caspase-3 proteins. After up-regulation of CKB expression, the proliferation ability of Huh-7 cells was enhanced, and the protein expression levels of Bcl-2 and MDM2 were elevated. The protein expression levels of p53, Bax, and caspase-3 were decreased. In addition, plumbagin reversed the effect of overexpression of CKB on the proliferation and apoptosis of Huh-7 cells. In conclusion, plumbagin significantly inhibited the proliferative ability of Huh-7 cells, and the mechanism may be related to the inhibition of CKB expression, activation of the p53 signaling pathway, and regulation of the expression of mitochondrial-associated apoptotic proteins, ultimately inducing cell apoptosis.


Subject(s)
Apoptosis , Carcinoma, Hepatocellular , Cell Proliferation , Liver Neoplasms , Naphthoquinones , Signal Transduction , Tumor Suppressor Protein p53 , Humans , Naphthoquinones/pharmacology , Apoptosis/drug effects , Cell Proliferation/drug effects , Carcinoma, Hepatocellular/genetics , Carcinoma, Hepatocellular/drug therapy , Carcinoma, Hepatocellular/metabolism , Tumor Suppressor Protein p53/genetics , Tumor Suppressor Protein p53/metabolism , Signal Transduction/drug effects , Liver Neoplasms/genetics , Liver Neoplasms/metabolism , Liver Neoplasms/drug therapy , Cell Line, Tumor , Proto-Oncogene Proteins c-mdm2/genetics , Proto-Oncogene Proteins c-mdm2/metabolism
3.
J Hepatocell Carcinoma ; 11: 565-580, 2024.
Article in English | MEDLINE | ID: mdl-38525157

ABSTRACT

Background/Aims: Plumbagin (PL) has been shown to effe ctively inhibit autophagy, suppressing invasion and migration of hepatocellular carcinoma (HCC) cells. However, the specific mechanism remains unclear. This study aimed to investigate the effect of PL on tumor growth factor (TGF)-ß-induced epithelial-mesenchymal transition (EMT) in HCC. Methods: Huh-7 cells were cultured, and in vivo models of EMT and HCC-associated lung metastasis were developed through tail vein and in situ injections of tumor cells. In vivo imaging and hematoxylin and eosin staining were used to evaluate HCC modeling and lung metastasis. After PL intervention, the expression levels of Snail, vimentin, E-cadherin, and N-cadherin in the liver were evaluated through immunohistochemistry and Western blot. An in vitro TGF-ß-induced cell EMT model was used to detect Snail, vimentin, E-cadherin, and N-cadherin mRNA levels through a polymerase chain reaction. Their protein levels were detected by immunofluorescence staining and Western blot. Results: In vivo experiments demonstrated that PL significantly reduced the expression of Snail, vimentin, and N-cadherin, while increasing the expression of E-cadherin at the protein levels, effectively inhibiting HCC and lung metastasis. In vitro experiments confirmed that PL up-regulated epithelial cell markers, down-regulated mesenchymal cell markers, and inhibited EMT levels in HCC cells. Conclusion: PL inhibits Snail expression, up-regulates E-cadherin expression, and down-regulates N-cadherin and vimentin expression, preventing EMT in HCC cells and reducing lung metastasis.

4.
Front Aging Neurosci ; 15: 1146660, 2023.
Article in English | MEDLINE | ID: mdl-37032823

ABSTRACT

Introduction: Alzheimer's disease (AD) is a common neurodegenerative disease. The concealment of the disease is the difficulty of its prevention and treatment. Previous studies have shown that mitophagy is crucial to the development of AD. However, there is a lack of research on the identification and clinical significance of mitophagy-related genes in AD. Therefore, the purpose of this study was to identify the mitophagy-related genes with the diagnostic potential for AD and establish a diagnostic model for AD. Methods: Firstly, we download the AD gene expression profile from Gene Expression Omnibus (GEO). Limma, PPI, functional enrichment analysis and WGCNA were used to screen the differential expression of mitophagy-related AD gene. Then, machine learning methods (random forest, univariate analysis, support vector machine, LASSO regression and support vector machine classification) were used to identify diagnostic markers. Finally, the diagnostic model was established and evaluated by ROC, multiple regression analysis, nomogram, calibration curve and other methods. Moreover, multiple independent datasets, AD cell models and AD clinical samples were used to verify the expression level of characteristic genes in the diagnostic model. Results: In total, 72 differentially expressed mitophagy-related related genes were identified, which were mainly involved in biological functions such as autophagy, apoptosis and neurological diseases. Four mitophagy-related genes (OPTN, PTGS2, TOMM20, and VDAC1) were identified as biomarkers. A diagnostic prediction model was constructed, and the reliability of the model was verified by receiver operating characteristic (ROC) curve analysis of GSE122063 and GSE63061. Then, we combine four mitophagy-related genes with age to establish a nomogram model. The ROC, C index and calibration curve show that the model has good prediction performance. Finally, multiple independent datasets, AD cell model samples and clinical peripheral blood samples confirmed that the expression levels of four mitophagy-related genes were consistent with the results of bioinformatics analysis. Discussion: The analysis results and diagnostic model of this study are helpful for the follow-up clinical work and mechanism research of AD.

5.
Small ; 18(21): e2200436, 2022 05.
Article in English | MEDLINE | ID: mdl-35491392

ABSTRACT

The fuel cell is a basic device to generate electricity from chemical fuels. It is often operated with oxygen as the oxidizing agent, but its sluggish reduction has become a key challenge. Herein, a conceptual oxygen-free design is demonstrated, namely a zinc-nitrate fuel cell, which converts nitrate waste into valuable ammonia and generates electricity simultaneously. The cell is constructed with zinc foil as the anode and ruthenium (Ru) nanoparticles loaded on nickel foam as the cathode. Catalyzed by Ru/Ni hydroxide hybrid, the reaction rate of 384 mmol h-1  mgRu-1 (1.4 × 10-6  ± 0.1 × 10-6  mol s-1  cm-2 ) and Faradic efficiency (FENH3  = 97% ± 2%) at -0.6 V versus reverse hydrogen electrode are achieved for nitrate-to-ammonia conversion. During ammonia production, such zinc-nitrate fuel cell can further deliver a maximum power density of 51.5 mW cm-2 (0.25 cm2  electrode) and 23.3 mW cm-2  (1 cm2 electrode), keeping ultrahigh Faradic efficiency (97% ± 4% at 40 mA cm-2 ) after long tests.


Subject(s)
Nitrates , Ruthenium , Ammonia , Electrodes , Hydroxides , Oxygen , Zinc
6.
Chem Biodivers ; 19(3): e202100876, 2022 Mar.
Article in English | MEDLINE | ID: mdl-35098641

ABSTRACT

Although the effect of pearl powder has been recognized for more than a thousand years from healthcare to beauty care, there has yet to be an in-depth understanding of its anti-photoaging effect. In the present study, the protective effect of pearl extract (PE) on UV-induced photoaging in mice was evaluated. First, the amino acid analysis of PE was carried out. Then, different dosages of pearl extract gel (PEG) were applied topically on the shaved dorsal skins regions of mice before UV irradiation. Skin physiological and histological analysis, antioxidant enzymes and inflammatory factor test were used to evaluate the anti-photoaging effect of PEG. The results showed that PEG contained 14 amino acids, and could inhibit UV-irritated skin wrinkles, laxity, thickness, and dryness. Moreover, PEG upregulated the activities of CAT, GSH-Px, SOD and decreased MDA level, and suppressed the production of IL-1ß, IL-6, PGE2 , TNF-α, and COX-2 in UV-irradiated mice. The therapeutic effect in high dose PEG group was superior to those of positive control (Vitamin E). This study demonstrated the underlying mechanisms of PEG against UV-irritated photoaging. And PEG possesses a potential use in photoprotective medicines and cosmetics.


Subject(s)
Pinctada , Skin Aging , Animals , Calcium Carbonate , Mice , Plant Extracts/metabolism , Plant Extracts/pharmacology , Skin , Ultraviolet Rays/adverse effects
7.
Phytother Res ; 36(1): 53-61, 2022 Jan.
Article in English | MEDLINE | ID: mdl-34510592

ABSTRACT

The present study aims to summarize and quantitatively examine the available evidence on the effectiveness of anthocyanin supplementation on liver enzymes among patients with metabolic disorders, by employing a systematic review and meta-analytic approach. Online databases including PubMed/Medline, Scopus, ISI Web of Science, and Cochrane Library were searched up to June 2020 for randomized controlled trials (RCTs) that examined the effect of anthocyanin supplementation on serum levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) among patients with metabolic disorders. To estimate the overall effect of anthocyanin supplementation, we employed the random-effects model. In total, 12 RCTs were included in the systematic review. Pooled analysis did not show any significant changes in ALT (WMD: -0.92 U/L, 95% CI: -4.19 to 2.35, p = .58; I2  = 91.3%) and AST (WMD: -1.22 U/L, 95% CI: -3.43 to 0.99, p = .28; I2  = 87.0) concentrations after supplementation with anthocyanin. The dose and duration of supplementation were the potential sources of heterogeneity among most of the trials. However, subgroup analysis showed that the effect is not statistically significant in all subgroups. Overall, in our study, anthocyanin does not have any effect on liver enzyme levels significantly. However, future high-quality studies are still needed to confirm the results.


Subject(s)
Anthocyanins , Metabolic Diseases , Dietary Supplements , Humans , Liver , Metabolic Diseases/drug therapy , Randomized Controlled Trials as Topic
8.
Langmuir ; 37(50): 14657-14667, 2021 Dec 21.
Article in English | MEDLINE | ID: mdl-34874741

ABSTRACT

Graphene-based structures have been widely reported as promising metal-free catalysts for nitrogen reduction reaction. To explain the reactivity origin, various structures have been proposed and debated, including defects, functional groups, and doped heteroatoms. This computational work demonstrates that these structures may evolve from one to another under electrochemical conditions, generating weakly coordinated carbons, which have been identified as the active sites for N2 adsorption and activation.

10.
Ann Palliat Med ; 10(6): 6617-6629, 2021 Jun.
Article in English | MEDLINE | ID: mdl-34154340

ABSTRACT

BACKGROUND: Traditional Chinese medicine (TCM) has demonstrated excellent effects in treating diabetic nephropathy, and Yiqi Huoxue prescription has been widely used clinically. In the study, its effects on the kidney function and blood glucose of patients were explored. METHODS: Chinese and English databases including PubMed, Medline, Embase, and Web of Sciences were used to retrieve articles comparing the treatment of diabetic nephropathy using Yiqi Huoxue prescription on the basis of conventional Western medicine treatment (experimental group) and conventional Western medicine treatment alone (control group) published from January 2000 to December 2020. The risk of bias assessment tool of the Cochrane System Review Manual 5.2.2 and the Jadad scale were used to evaluate the quality of the included literature. The outcome indexes were extracted, and the Review Manager 5.3 software was used for meta-analysis. RESULTS: A total of 13 articles that satisfied the inclusion/exclusion criteria were included in this study. After treatment, compared to the control group, the experimental group exhibited lower urine microalbumin excretion rate (UAER) [mean difference (MD) =-33.94, 95% confidence interval (CI), -42.60 to -25.28, P<0.00001], serum creatinine (SCr) (MD =-7.43, 95% CI, -11.50 to -3.36, P=0.0004), blood urea nitrogen (BUN) (SMD =-1.23, 95% CI, -2.49 to 0.03, P=0.04), blood glucose-related indexes [fasting blood glucose (FBG)] (MD =-0.43, 95% CI, -0.87 to 0.01, P=0.03), glycosylated hemoglobin (HbA1c) (MD =-0.38, 95% CI, -0.68 to -0.08, P=0.01), blood lipid-related indexes [triglycerides (TG)] (MD =-0.44, 95% CI, -0.76 to -0.13, P=0.006), and serum total cholesterol (TC) (MD =-0.37, 95% CI, -0.57 to -0.18, P=0.0002). Furthermore, the experimental group also showed higher effectiveness rate (odds ratio =3.81, 95% CI, 2.71 to 5.35, P<0.00001) after treatment. DISCUSSION: The included literature had low bias risk. Yiqi Huoxue prescription on the basis of conventional Western medicine can significantly improve the renal function and reduce the levels of blood glucose and blood lipids of patients with diabetic nephropathy.


Subject(s)
Diabetes Mellitus , Diabetic Nephropathies , Blood Glucose , Diabetic Nephropathies/drug therapy , Humans , Medicine, Chinese Traditional , Prescriptions
11.
Ann Palliat Med ; 10(5): 5366-5372, 2021 May.
Article in English | MEDLINE | ID: mdl-34044553

ABSTRACT

BACKGROUND: Peripheral artery disease (PAD) is a common chronic complication of type 2 diabetes (T2DM). This study sought to evaluate the effect of supervised exercise therapy (SET) on patients with PAD complicated with T2DM, and to assess the effect of changes in sedentary time on the results of SET treatment. METHODS: A total of 100 PAD patients who were treated in our hospital from January 2019 to October 2020 were included, and the age, gender, body mass index (BMI), hypertension, smoking, and ankle brachial index (ABI) were collected. The patients were required to complete SET treatment 2-3 times a week for 12 weeks. Subsequently, the objective 6-minute walk test (6MWT) and Short Physical Performance Battery (SPPB) were used to assess body function. After adjusting for other key confounding variables such as age, gender, and smoking status, linear regression analysis was used to evaluate the effects of changes in sedentary time on the total distance of the 6MWT. RESULTS: After 12 weeks of treatment, the total SPPB score of the patients increased from a baseline of 9.3±2.7 to 10.1±2.3 (P=0.025), the normal walking distance in the 6MWT increased from 108.9±26.8 to 148.9±29.5 m (P<0.001), the total walking distance increased from 322.5±93.4 to 348.5±86.1 m (P=0.042), and at the same time, the metabolic equivalent on the treadmill increased from 2.6±0.7 to 3.9±1.4 (P<0.001). Compared with the baseline data, the proportion of time that patients spent engaged in mild physical activity at 6 weeks increased by 20%±10% (P=0.003), and the average daily sedentary time decreased by 6.5±2.8 minutes (P=0.008), or by 3.1%±2.1% (P=0.04). Furthermore, compared with the baseline, the proportion of time that patients spent engaged in light and moderate physical activity at 12 weeks increased by 10%±3% (P=0.007) and 20%±10% (P=0.006), respectively, while the average sedentary time per day reduced by 6.8±3.1 minutes (P=0.03), or by 3.6%±1.8% (P=0.005). CONCLUSIONS: The reduction of sedentary time can significantly improve the effectiveness of exercise therapy in patients with PAD complicated by T2DM, and compared with patients with PAD alone, the improvement in patients complicated with T2DM is more significant.


Subject(s)
Diabetes Mellitus, Type 2 , Peripheral Arterial Disease , Diabetes Mellitus, Type 2/therapy , Exercise Therapy , Humans , Intermittent Claudication , Peripheral Arterial Disease/therapy , Sedentary Behavior , Walking
12.
Adv Mater ; 32(40): e2004382, 2020 Oct.
Article in English | MEDLINE | ID: mdl-32876982

ABSTRACT

Electrochemical nitrogen reduction reaction (NRR) over nonprecious-metal and single-atom catalysts has received increasing attention as a sustainable strategy to synthesize ammonia. However, the atomic-scale regulation of such active sites for NRR catalysis remains challenging because of the large distance between them, which significantly weakens their cooperation. Herein, the utilization of regular surface cavities with unique microenvironment on graphitic carbon nitride as "subnano reactors" to precisely confine multiple Fe and Cu atoms for NRR electrocatalysis is reported. The synergy of Fe and Cu atoms in such confined subnano space provides significantly enhanced NRR performance, with nearly doubles ammonia yield and 54%-increased Faradic efficiency up to 34%, comparing with the single-metal counterparts. First principle simulation reveals this synergistic effect originates from the unique Fe-Cu coordination, which effectively modifies the N2 absorption, improves electron transfer, and offers extra redox couples for NRR. This work thus provides new strategies of manipulating catalysts active centers at the sub-nanometer scale.

14.
Chem Commun (Camb) ; 53(44): 5950-5953, 2017 May 30.
Article in English | MEDLINE | ID: mdl-28417120

ABSTRACT

This work presents a new strategy for the promotion of CO2 uptake by an intramolecular proton transfer reaction in amino functionalized hydroxypyridine based anions.

15.
ChemSusChem ; 10(7): 1509-1516, 2017 04 10.
Article in English | MEDLINE | ID: mdl-28133917

ABSTRACT

Palladium nanoparticles are effective for catalytic CO2 reduction. However, CO, one of the most important products in the CO2 reduction sequence, has strong affinity for the Pd surface and poisons the catalytic sites rapidly. In this research, an electrodeposited Pd film exhibits high activity for CO2 reduction to formate with the suppression of CO formation at low overpotentials. The substrates, electrodeposition process and the post-treatment of the Pd films affect the CO2 reduction pathway significantly. The cyclic voltammetry deposition produces films that exhibit more porous morphologies and have higher current efficiencies for formate than those of films produced at constant potential. These films show stable CO2 reduction performance at low overpotentials and have high current efficiencies (≈50-60 % depending on the substrate) for formate formation at a potential of -0.4 V versus the reversible hydrogen electrode without any detectable CO formation. It seems that the Pd surface generated by the new electrodeposition process described here produces a nanostructure that can promote formate formation and suppress CO formation.


Subject(s)
Carbon Dioxide/chemistry , Electroplating , Formates/chemistry , Palladium/chemistry , Catalysis , Electrochemistry , Electrodes
16.
ACS Appl Mater Interfaces ; 8(51): 35243-35252, 2016 Dec 28.
Article in English | MEDLINE | ID: mdl-27977114

ABSTRACT

Protic salts have been recently recognized to be an excellent carbon source to obtain highly ordered N-doped carbon without the need of tedious and time-consuming preparation steps that are usually involved in traditional polymer-based precursors. Herein, we report a direct co-pyrolysis of an easily synthesized protic salt (benzimidazolium triflate) with calcium and sodium citrate at 850 °C to obtain N-doped mesoporous carbons from a single calcination procedure. It was found that sodium citrate plays a role in the final carbon porosity and acts as an in situ activator. This results in a large surface area as high as 1738 m2/g with a homogeneous pore size distribution and a moderate nitrogen doping level of 3.1%. X-ray photoelectron spectroscopy (XPS) measurements revealed that graphitic and pyridinic groups are the main nitrogen species present in the material, and their content depends on the amount of sodium citrate used during pyrolysis. Transmission electron microscopy (TEM) investigation showed that sodium citrate assists the formation of graphitic domains and many carbon nanosheets were observed. When applied as supercapacitor electrodes, a specific capacitance of 111 F/g in organic electrolyte was obtained and an excellent capacitance retention of 85.9% was observed at a current density of 10 A/g. At an operating voltage of 3.0 V, the device provided a maximum energy density of 35 W h/kg and a maximum power density of 12 kW/kg.

17.
Nat Commun ; 7: 11335, 2016 Apr 20.
Article in English | MEDLINE | ID: mdl-27093916

ABSTRACT

Ammonia (NH3) is one of the most widely produced chemicals worldwide. It has application in the production of many important chemicals, particularly fertilizers. It is also, potentially, an important energy storage intermediate and clean energy carrier. Ammonia production, however, mostly uses fossil fuels and currently accounts for more than 1.6% of global CO2 emissions (0.57 Gt in 2015). Here we describe a solar-driven nanostructured photoelectrochemical cell based on plasmon-enhanced black silicon for the conversion of atmospheric N2 to ammonia producing yields of 13.3 mg m(-2) h(-1) under 2 suns illumination. The yield increases with pressure; the highest observed in this work was 60 mg m(-2) h(-1) at 7 atm. In the presence of sulfite as a reactant, the process also offers a direct solar energy route to ammonium sulfate, a fertilizer of economic importance. Although the yields are currently not sufficient for practical application, there is much scope for improvement in the active materials in this cell.

18.
Angew Chem Int Ed Engl ; 54(29): 8420-4, 2015 Jul 13.
Article in English | MEDLINE | ID: mdl-26032183

ABSTRACT

Acid catalytic processes play a classic and important role in modern organic synthesis. How well the acid can be controlled often plays the key role in the controllable synthesis of the products with high conversion yield and selectivity. The preparation of a novel, photo-switchable solid-acid catalyst based on carbon quantum dots is described. The carbon quantum dots are decorated with small amounts of hydrogensulfate groups and thus exhibit a photogenerated acidity that produces a highly efficient acid catalysis of the ring opening of epoxides with methanol and other primary alcohols. This reversible, light-switchable acidity is shown to be due to photoexcitation and charge separation in the carbon quantum dots, which create an electron withdrawing effect from the acidic groups. The catalyst is easily separated by filtration, and we demonstrate multiple cycles of its recovery and reuse.


Subject(s)
Carbon/chemistry , Epoxy Compounds/chemistry , Methanol/chemistry , Quantum Dots/chemistry , Sulfates/chemistry , Catalysis , Light
19.
ChemSusChem ; 8(11): 1980-5, 2015 Jun 08.
Article in English | MEDLINE | ID: mdl-25940315

ABSTRACT

Manganese oxides (MnOx ) are considered to be promising catalysts for water oxidation. Building on our previous studies showing that the catalytic activity of MnOx films electrodeposited from aqueous electrolytes is improved by a simple heat treatment, we have explored the origin of the catalytic enhancement at an electronic level by X-ray absorption spectroscopy (XAS). The Mn L-edge XA spectra measured at various heating stages were fitted by linear combinations of the spectra of the well-defined manganese oxides-MnO, Mn3 O4 , Mn2 O3 , MnO2 and birnessite. This analysis identified two major manganese oxides, Mn3 O4 and birnessite, that constitute 97 % of the MnOx films. Moreover, the catalytic improvement on heat treatment at 90 °C is related to the conversion of a small amount of birnessite to the Mn3 O4 phase, accompanied by an irreversible dehydration process. Further dehydration at higher temperature (120 °C), however, leads to a poorer catalytic performance.


Subject(s)
Hot Temperature , Manganese Compounds/chemistry , Oxides/chemistry , Water/chemistry , Catalysis , Electrochemistry , Oxidation-Reduction
20.
ChemSusChem ; 6(4): 643-51, 2013 Apr.
Article in English | MEDLINE | ID: mdl-23460606

ABSTRACT

Manganese oxides (MnOx ) are considered to be promising catalysts for water oxidation. Electrodeposited MnOx films from aqueous electrolytes have previously been shown to exhibit a lower catalytic action than films deposited from ionic liquids when tested in strongly alkaline conditions. In this study, we describe a thermal treatment that converts the MnOx films deposited from aqueous electrolytes to highly catalytic films with comparable activity to ionic-liquid-deposited films. The films deposited from aqueous electrolytes show a remarkable improvement in the catalysis of water oxidation after heat treatment at a low temperature (≤120 °C) for 30 min. The films were characterised by using XRD and SEM, and energy-dispersive X-ray (EDX), FTIR and Raman spectroscopy, which indicate that dehydration occurs during the heat treatment without significant change to the microstructure or bulk composition. The X-ray absorption spectroscopy (XAS) results show the growth of small amounts (ca. 3-10 %) of reduced Mn species (Mn(II) or Mn(III) ) after heat treatment. The dehydration process removes structural water and hydroxyl species to result in a conductivity improvement and a more active catalyst, thereby contributing to the enhancement in water oxidation performance.


Subject(s)
Manganese Compounds/chemistry , Oxides/chemistry , Water/chemistry , Catalysis , Hot Temperature , Microscopy, Electron, Scanning , Oxidation-Reduction , Spectroscopy, Fourier Transform Infrared , Spectrum Analysis, Raman , X-Ray Absorption Spectroscopy , X-Ray Diffraction
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