Solvothermal synthesis has shown to have a great potential to synthesize Zinc Oxide nanoparticles (ZnO NPs) with less than 10 nm size. In this study, we present a rapid synthesis of ZnO NPs in which ...ZnO NPs with more uniform shape and highly dispersed were synthesized using zinc acetate dihydrate (Zn(CH3COO)2 2H2O) and potassium hydroxide (KOH) as a precursor and absolute ethanol as solvent via solvothermal method. Few techniques were exploited to characterize synthesized ZnO NPs including X-ray diffraction (XRD), transmission electron microscope (TEM), Brunauer-Emmett-Teller (BET), energy-dispersive X-ray spectroscopy (EDX), fourier transform infrared (FT-IR) spectroscopy, and ultraviolet visible (UV-Vis) spectroscopy. Synthesized ZnO NPs that were prepared via solvothermal synthesis method at 60 °C for 3 hours exhibited a wurtzite structure with a crystalline size of 10.08 nm and particle size of 7.4 ± 1.2 nm. The UV-vis absorption spectrum has shown peak at 357 nm indicate the presence of ZnO NPs. Hence, better quality with uniform size ZnO NPs can be easily synthesized with reduced amount of time via solvothermal synthesis method rather than using other complicated and lengthy synthesis methods.
•Variations in the Fe-Pani precursor to RGO biomass ratio led to different ORR performance•Highly accessible FeN2 and FeN4 hosted on micropores improved the ORR activity•Meso/macropores could ...increase mass transport and improve catalyst stability•A balance between micropores and meso/macropores is crucial to achieve high PEMFC performance
Pyrolysed Fe-N-C catalysts are foreseen to be promising noble-free cathode catalysts for proton exchange membrane fuel cells. Nevertheless, efforts are required to overcome active site degradation, which is influenced by the meso/macroporous composition of the catalyst and support. Reduced graphene oxide from Sengon wood is seen as a potential support for Fe-polyaniline (Pani) catalysts due to its hierarchical porous structure that depends on N/C ratio. This work reveals that the Fe-N4 moiety serves as the active site, which is confirmed by XPS and first-principles calculations. Fe-Pani-RGO 2:0.2, with the highest content of Fe-N4 and specific surface area, results in the highest ORR activity with Eonset =0.84 V, E1/2 = 0.79 V, and JD = 5.5 mA/cm2. Although micropores are important for hosting the active sites that contribute to high ORR activity, in regard to single-cell performance, the role of meso‑/macropores is crucial for achieving higher overall performance.
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•Gamma radiolysis is used for synthesizing palladium particles on graphene oxide support.•The concentration of the Pd precursor affects the loading, size, and distribution of Pd ...particles.•Gamma-radiolysis synthesized Pd/GO samples show excellent activity for ORR.•Gamma irradiation enhances electron transfer and reduces peroxide yield in Pd/GO.•This research offers a convenient technique for synthesizing and modifying Pd/GO as an ORR electrocatalyst.
This work aims to investigate the preparation of palladium (Pd) particles on graphene oxide (GO) support via gamma radiolysis and to study their electrochemical activity towards the oxygen reduction reaction (ORR). The results show that the Pd precursor concentration used in the preparation process influences the loading, size, and distribution of the Pd particles. The electrochemical analysis shows that the Pd/GO samples synthesized through gamma radiolysis exhibit excellent activity toward ORR. Additionally, the gamma irradiation used in the synthesis process shows beneficial effects on the Pd/GO. High gamma irradiation doses increase the electron transfer number and reduce the peroxide yield of the Pd/GO.
Although traditional chemotherapy kills a fraction of tumor cells, it also activates the stroma and can promote the growth and survival of residual cancer cells to foster tumor recurrence and ...metastasis. Accordingly, overcoming the host response induced by chemotherapy could substantially improve therapeutic outcome and patient survival. In this study, resistance to treatment and metastasis has been attributed to expansion of stem-like tumor-initiating cells (TICs). Molecular analysis of the tumor stroma in neoadjuvant chemotherapy-treated human desmoplastic cancers and orthotopic tumor xenografts revealed that traditional maximum-tolerated dose chemotherapy, regardless of the agents used, induces persistent STAT-1 and NF-κB activity in carcinoma-associated fibroblasts. This induction results in the expression and secretion of ELR motif-positive (ELR
) chemokines, which signal through CXCR-2 on carcinoma cells to trigger their phenotypic conversion into TICs and promote their invasive behaviors, leading to paradoxical tumor aggression after therapy. In contrast, the same overall dose administered as a low-dose metronomic chemotherapy regimen largely prevented therapy-induced stromal ELR
chemokine paracrine signaling, thus enhancing treatment response and extending survival of mice carrying desmoplastic cancers. These experiments illustrate the importance of stroma in cancer therapy and how its impact on treatment resistance could be tempered by altering the dosing schedule of systemic chemotherapy.
This work reports utilised of RGO from Sengon wood biomass to support Fe–N–C noble-free catalyst (Fe–N-RGO), while also attempt to investigate the effect of pyrolysis stage on Fe–N-RGO catalysts with ...four different nitrogen precursors towards the ORR activity in acidic medium. One- and two-step pyrolysis were performed at 900 °C for 1 h and 2 h respectively to produce Fe–N-RGO. This work revealed that two-step pyrolysis was able to remove the volatile components and hence forming more graphitised, stable graphitic-N and Fe-Nx, synergistically improve the ORR activity with highest onset potential of 0.83 V vs RHE and limiting current density of 5.33 mA cm−2 reported on Fe-Pani-RGO 2py. An increase in the kinetic on Fe-Pani-RGO 2py with Tafel slope of 74 mV/dec operated at 80 °C was reported. The mesoporous structure on RGO increases the stability by 8% and better methanol tolerance when compared to a benchmark Pt/C catalyst.
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•RGO produced from biomass improved mass transport of oxygen.•Improved ORR activity observed on Fe-Pani-RGO upon two-step pyrolysis.•Graphitic N, Fe-Nx and mesopores contribute to improved ORR activity.
Electrocatalysts are used to promote efficient energy conversion in fuel cell, especially for the sluggish oxygen reduction reaction (ORR) at the cathode that inhibits the performance of the device. ...In this work, we demonstrate the use of a facile gamma radiolysis technique to synthesize carbon nanotube-supported palladium (Pd) metal particles as electrocatalysts for the ORR application. The Pd precursor concentration used in the preparation process was found to contribute greater effects on the Pd content and Pd crystallite size of the synthesized product compared to the gamma irradiation dose. The results showed that gamma radiolysis could successfully reduce Pd ions from its precursor solution as evidenced from field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) characterization. The optimal ORR electrocatalyst was prepared using 0.01-M Pd precursor and a gamma radiation dose of 50 kGy. It displays a high half-wave potential (
E
1/2
) of 0.84 V (vs. RHE) and superior electron transfer number (
n
) of 3.96, as well as a low peroxide yield of 1.8%. This impressive ORR electrocatalytic performance was also attributed to the synergistic effect of Pd metal particles with CNT. The findings showed that Pd/CNT is a promising electrocatalyst for ORR application and that gamma radiolysis provides a facile and eco-friendly approach in synthesizing electrocatalysts.
Abstract
Graphene can be produced from graphite rod of a battery by electrochemical exfoliation process in acidic electrolytes. This process is simple, safe, fast, cheap and produces graphene in ...large scale. Parameters to be controlled during the process are the concentration of the electrolytes and potential for exfoliation. The synthesized graphene was characterized by Raman Spectroscopy and Field Emission Scanning Electron Microscopy (FESEM). From the results, it was found that graphene synthesized with 90:10 volume ratio had better yield, lowest interlayer distance, less oxidation and minimum defect of graphene.
The aim of this study is to produce noble-metal-free oxygen reduction reaction (ORR) catalyst via irradiation. Gamma ray irradiation reduction has been utilized to produce N-doped reduced graphene ...oxide (rGO)-supported iron (Fe)-based catalysts, whose weight percent (wt.%) of Fe loading varies from 10% to 20%. In this study, the physicochemical properties of Fe/N-rGO with various loadings of Fe (10 wt.%, 15 wt.% and 20 wt.%) were explored through X-ray diffraction (XRD), field emission scanning electron microscopy-energy dispersive spectroscopy (FESEM-EDS), Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR). XRD showed that a broad-peak nanocrystallite Fe2O3 phase formed. Raman spectroscopy revealed that Fe insertion increased the disordered GO structure. Fourier transform infrared (FTIR) demonstrated that N was functionalized into rGO. FESEM-EDX presented that Fe nanoparticles existed on the wrinkled rGO surface but their amount was low. Linear sweep voltammetry (LSV) was performed with a rotating disk electrode in 0.1 M KOH at a scanning rate of 20 mVs−1 and revolution rates of 400, 900 and 1600 rpm and the corresponding electron transfer numbers were investigated with a Koutecky–Levich model. This model indicated that the number of electron transfers of 20% Fe/N-rGO was above 2 and its performance toward ORR was higher than those of 10% Fe/N-rGO and 15% Fe/N-rGO.
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