scholarly journals The Synergistic Effects of Alloying on the Performance and Stability of Co3Mo and Co7Mo6 for the Electrocatalytic Hydrogen Evolution Reaction

Hydrogen ◽  
2020 ◽  
Vol 1 (1) ◽  
pp. 11-21
Author(s):  
Youyi Sun ◽  
Alexey Y. Ganin
Keyword(s):  
Hydrogen Evolution ◽  
Synergistic Effects ◽  
Alkaline Media ◽  
Price Of Stability ◽  
X Ray Diffraction ◽  
Free Standing ◽  
X Ray ◽  
Current Decay ◽  
Earth Abundant ◽  
Current Densities

Metal alloys have become a ubiquitous choice as catalysts for electrochemical hydrogen evolution in alkaline media. However, scarce and expensive Pt remains the key electrocatalyst in acidic electrolytes, making the search for earth-abundant and cheaper alternatives important. Herein, we present a facile and efficient synthetic route towards polycrystalline Co3Mo and Co7Mo6 alloys. The single-phased nature of the alloys is confirmed by X-ray diffraction and electron microscopy. When electrochemically tested, they achieve competitively low overpotentials of 115 mV (Co3Mo) and 160 mV (Co7Mo6) at 10 mA cm−2 in 0.5 M H2SO4, and 120 mV (Co3Mo) and 160 mV (Co7Mo6) at 10 mA cm−2 in 1 M KOH. Both alloys outperform Co and Mo metals, which showed significantly higher overpotentials and lower current densities when tested under identical conditions, confirming the synergistic effect of the alloying. However, the low overpotential in Co3Mo comes at the price of stability. It rapidly becomes inactive when tested under applied potential bias. On the other hand, Co7Mo6 retains the current density over time without evidence of current decay. The findings demonstrate that even in free-standing form and without nanostructuring, polycrystalline bimetallic electrocatalysts could challenge the dominance of Pt in acidic media if ways for improving their stability were found.

scholarly journals Investigation of Co3Mo and Co6Mo7 Binary Alloys as Electrocatalysts for Hydrogen Evolution Reaction in Acidic Media

2020 ◽  
Author(s):  
youyi sun ◽  
Alexey Ganin
Keyword(s):  
Hydrogen Evolution ◽  
Metal Alloys ◽  
Alkaline Media ◽  
Price Of Stability ◽  
Applied Potential ◽  
Acidic Media ◽  
Free Standing ◽  
Current Decay ◽  
Earth Abundant ◽  
Current Densities

Metal alloys have become ubiquitous choice as catalysts for electrochemical hydrogen evolution in alkaline media. However, scarce and expensive Pt remains the key electrocatalyst in acidic electrolytes making the search for earth-abundant and cheaper alternatives appealing. Herein, we present a facile and efficient synthetic route towards polycrystalline Co<sub>3</sub>Mo and Co<sub>6</sub>Mo<sub>7</sub> metal alloys that achieve competitively low overpotentials of 115 mV and 160 mV at 10 mA cm<sup>–2</sup> in 0.5 M H<sub>2</sub>SO<sub>4</sub>. Both alloys outperform Co and Mo metals which showed significantly higher overpotentials and lower current densities when tested under identical conditions. However, the low overpotential in Co<sub>3</sub>Mo comes at the price of stability. It rapidly becomes inactive when tested under applied potential bias. On the other hand, Co<sub>7</sub>Mo<sub>6</sub> retains the current density over time without the evidence of current decay. The findings demonstrate that even in free-standing form and without nanostructuring polycrystalline bimetallic electrocatalysts could challenge the dominance of Pt in the acidic media if the ways for improving their stability were found.

scholarly journals Investigation of Co3Mo and Co6Mo7 Binary Alloys as Electrocatalysts for Hydrogen Evolution Reaction in Acidic Media

2020 ◽  
Author(s):  
youyi sun ◽  
Alexey Ganin
Keyword(s):  
Hydrogen Evolution ◽  
Metal Alloys ◽  
Alkaline Media ◽  
Price Of Stability ◽  
Applied Potential ◽  
Acidic Media ◽  
Free Standing ◽  
Current Decay ◽  
Earth Abundant ◽  
Current Densities

Metal alloys have become ubiquitous choice as catalysts for electrochemical hydrogen evolution in alkaline media. However, scarce and expensive Pt remains the key electrocatalyst in acidic electrolytes making the search for earth-abundant and cheaper alternatives appealing. Herein, we present a facile and efficient synthetic route towards polycrystalline Co<sub>3</sub>Mo and Co<sub>6</sub>Mo<sub>7</sub> metal alloys that achieve competitively low overpotentials of 115 mV and 160 mV at 10 mA cm<sup>–2</sup> in 0.5 M H<sub>2</sub>SO<sub>4</sub>. Both alloys outperform Co and Mo metals which showed significantly higher overpotentials and lower current densities when tested under identical conditions. However, the low overpotential in Co<sub>3</sub>Mo comes at the price of stability. It rapidly becomes inactive when tested under applied potential bias. On the other hand, Co<sub>7</sub>Mo<sub>6</sub> retains the current density over time without the evidence of current decay. The findings demonstrate that even in free-standing form and without nanostructuring polycrystalline bimetallic electrocatalysts could challenge the dominance of Pt in the acidic media if the ways for improving their stability were found.

scholarly journals The effect of cobalt on morphology, structure, and ORR activity of electrospun carbon fibre mats in aqueous alkaline environments

2021 ◽  
Vol 12 ◽  
pp. 1173-1186
Author(s):  
Markus Gehring ◽  
Tobias Kutsch ◽  
Osmane Camara ◽  
Alexandre Merlen ◽  
Hermann Tempel ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Inductively Coupled Plasma ◽  
Elevated Temperatures ◽  
Current Collector ◽  
Alkaline Media ◽  
Emission Spectrometry ◽  
Free Standing ◽  
X Ray ◽  
Turbostratic Carbon ◽  
Current Densities

An innovative approach for the design of air electrodes for metal–air batteries are free-standing scaffolds made of electrospun polyacrylonitrile fibres. In this study, cobalt-decorated fibres are prepared, and the influence of carbonisation temperature on the resulting particle decoration, as well as on fibre structure and morphology is discussed. Scanning electron microscopy, Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, elemental analysis, and inductively coupled plasma optical emission spectrometry are used for characterisation. The modified fibre system is compared to a benchmark system without cobalt additives. Cobalt is known to catalyse the formation of graphite in carbonaceous materials at elevated temperatures. As a result of cobalt migration in the material the resulting overall morphology is that of turbostratic carbon. Nitrogen removal and nitrogen-type distribution are enhanced by the cobalt additives. At lower carbonisation temperatures cobalt is distributed over the surface of the fibres, whereas at high carbonisation temperatures it forms particles with diameters up to 300 nm. Free-standing, current-collector-free electrodes assembled from carbonised cobalt-decorated fibre mats display promising performance for the oxygen reduction reaction in aqueous alkaline media. High current densities at an overpotential of 100 mV and low overpotentials at current densities of 333 μA·cm−2 were found for all electrodes made from cobalt-decorated fibre mats carbonised at temperatures between 800 and 1000 °C.

scholarly journals Effect of Ni Doping on the MoS2 Structure and Its Hydrogen Evolution Activity in Acid and Alkaline Electrolytes

Surfaces ◽  
2019 ◽  
Vol 2 (4) ◽  
pp. 531-545 ◽  
Author(s):  
Dario Mosconi ◽  
Paul Till ◽  
Laura Calvillo ◽  
Tomasz Kosmala ◽  
Denis Garoli ◽  
...  
Keyword(s):  
Electronic Properties ◽  
Hydrogen Evolution ◽  
Three Dimensional ◽  
Linear Sweep Voltammetry ◽  
Alkaline Media ◽  
X Ray Diffraction ◽  
Ni Doping ◽  
X Ray ◽  
Structural And Electronic Properties ◽  
Alkaline Electrolytes

We have investigated three-dimensional (3D) MoS2 nanoarchitectures doped with different amount of Ni to boost the hydrogen evolution reaction (HER) in alkaline environment, where this reaction is normally hindered. As a comparison, the activity in acidic media was also investigated to determine and compare the role of the Ni sites in both media. The doping of MoS2, especially at high loadings, can modify its structural and/or electronic properties, which can also affect the HER activity. The structural and electronic properties of the Ni doped 3D-MoS2 nanoarchitecture were studied by X-ray diffraction (XRD), Raman spectroscopy, scanning and transmission electronic microscopy (SEM; TEM), and X-ray photoemission Spectroscopy (XPS). XPS also allowed us to determine the Ni-based species formed as a function of the dopant loading. The HER activity of the materials was investigated by linear sweep voltammetry (LSV) in 0.5 M H2SO4 and 1.0 M KOH. By combining the physicochemical and electrochemical results, we concluded that the Ni sites have a different role in the HER mechanism and kinetics in acidic and in alkaline media. Thus, NiSx species are essential to promote HER in alkaline medium, whereas the Ni-Mo-S ones enhance the HER in acid medium.

Immobilized Covalent Triazine Frameworks Films as Effective Photocatalysts for Hydrogen Evolution Reaction

2021 ◽  
Author(s):  
Xunliang Hu ◽  
Irshad Hussain ◽  
Bien Tan
Keyword(s):  
Hydrogen Evolution ◽  
Water Splitting ◽  
Crystalline Structure ◽  
Large Scale ◽  
Interfacial Polymerization ◽  
Point Of View ◽  
Lateral Size ◽  
Free Standing ◽  
X Ray ◽  
Synthetic Approaches

Abstract Covalent triazine frameworks (CTFs) have recently been demonstrated as promising materials for photocatalytic water splitting and are usually used in the form of suspended powder. From a practical point of view, immobilized CTFs materials are more suitable for large-scale water splitting applications, owing to their convenient separation and recycling potential. However, existing synthetic approaches mainly result in insoluble and unprocessable powders, which makes their future device application still a huge challenge. Herein, we report an aliphatic amine-assisted interfacial polymerization method to obtain free-standing, crystalline CTFs film with excellent photoelectric performance. The lateral size of the film was up to 250 cm2, the average thickness can be regulated from 30-500 nm. The crystalline structure was confirmed by high-resolution transmission electron microscope (HR-TEM), powder X-ray diffraction (PXRD), and small-angle X-ray scattering (SAXS) analysis. Intrigued by the good light absorption, crystalline structure, and big lateral size of the film, it was immobilized on a glass support that exhibited good photocatalytic hydrogen evolution performance (5.4 mmol h-1 m-2) and was easy to recycle.

scholarly journals A microstructural and corrosion resistance study of (Zr, Si, Ti)N-Ni coatings produced through co-sputtering

DYNA ◽  
2018 ◽  
Vol 85 (207) ◽  
pp. 192-197 ◽  
Author(s):  
Estrella Natali Borja-Goyeneche ◽  
Jhon Jairo Olaya-Florez
Keyword(s):  
Corrosion Resistance ◽  
Nickel Content ◽  
Corrosion Current ◽  
Nacl Solution ◽  
X Ray Diffraction ◽  
X Ray ◽  
X Ray Scattering ◽  
Current Densities ◽  
Fcc Phase

This work researches the influence of the nickel content on the structural and anticorrosive properties of ZrSiTiN films deposited by means of reactive co-sputtering on alloys of Ti6Al4V. The morphology and structure were analyzed by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD), and the chemical composition was identified via X-ray scattering spectroscopy (EDS). The corrosion resistance was studied using potentiodynamic polarization (PP) tests employing a 3.5% by weight NaCl solution. In the films, an increase of Ni up to 6.97 at% was observed, while in XRD the FCC phase of (Zr, Ti) N was identified, with a mixed orientation in planes (111) and (200), which tended to diminish with the increase of Ni. Finally, with the addition of Ni, the corrosion current densities were reduced from 5.56 𝑥 10−8 to 2.64 𝑥 10−9 𝐴/𝑐m2. The improvement in the corrosion resistance is due to the effect of the Ni on the microstructure of the system (Zr, Ti) N, which can improve the quality of the passive film and prevent crystalline defects and corrosion zones.

Residual stresses in chemical vapor deposition free-standing diamond films by X-ray diffraction analyses

2000 ◽  
Vol 288 (2) ◽  
pp. 217-222 ◽  
Author(s):  
O Durand ◽  
R Bisaro ◽  
C.J Brierley ◽  
P Galtier ◽  
G.R Kennedy ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Residual Stresses ◽  
Vapor Deposition ◽  
Diamond Films ◽  
Chemical Vapor ◽  
X Ray Diffraction ◽  
Free Standing ◽  
X Ray

EFFECT OF GRAIN SIZE ON THE FERROELECTRIC PROPERTIES OF Bi3.25La0.75Ti3O12 Thin Films

2002 ◽  
Vol 16 (28n29) ◽  
pp. 4469-4474 ◽  
Author(s):  
KYOUNG-TAE KIM ◽  
CHANG-IL KIM ◽  
DONG-HEE KANG ◽  
IL-WUN SHIM
Keyword(s):  
Thin Films ◽  
Grain Size ◽  
Remanent Polarization ◽  
Ferroelectric Properties ◽  
Fatigue Properties ◽  
X Ray Diffraction ◽  
X Ray ◽  
Current Densities ◽  
Metalorganic Decomposition ◽  
Small Grains

The Bi 3.25 La 0.75 Ti 3 O 12 (BLT) thin films were prepared by metalorganic decomposition method. The effect of grain size on the ferroelectric properties during crystallization were investigated by x-ray diffraction and field emission scanning electron microscope. The grain size and the roughness of BLT films increase with increasing of drying temperature. The leakage current densities of the BLT thin film with large grains are higher than that with small grains. The remanent polarization of BLT increase with increasing grain size. As compared BLT with small grain size, the BLT film with larger grain size shows better fatigue properties. This may be explained that small grained films shows more degradation of switching charge than large grained films.

X-ray Line Broadening Analysis of Tl-Superconducting Films

1989 ◽  
Vol 33 ◽  
pp. 145-151
Author(s):  
M. O. Eatough ◽  
D. S. Ginley ◽  
B. Morosin
Keyword(s):  
Thin Films ◽  
Superconducting Films ◽  
Electron Beam Evaporation ◽  
Superconducting Thin Films ◽  
Line Broadening ◽  
X Ray Diffraction ◽  
X Ray ◽  
Current Densities ◽  
Diffraction Peaks ◽  
Sequential Electron

AbstractSuperconducting thin films (0.3-0.7μm) in the TI-Ca-Ba-Cu-0 system have been prepared on various single crystal substrates by sequential electron beam evaporation followed by appropriate sintering and annealing. Oxygen-annealed films show Tc as high as 110K and critical current densities to 600,000 A/cm2. X-ray diffraction analyses of these films show predominantly the Tl2Ca2Ba2Cu2O10 phase (c-parameter near 36Å), but some also contain up to 50 at% of the Tl2CaBa2Cu2O8 phase (c-parameter near 30Å). The complete absence of hkl reflections other than 00I demonstrates the highly oriented nature of the films as well as the absence of other Tl phases. The diffraction peaks are noticeably broader for the 36Å phase than for the 30Å phase. For a 0.7μm film such broadening is consistent with coherent sizes along the c-axis of 1200 - 1400Å and 500Å, respectively, for the 30Å and 36Å phases, and of strain values near 1.4-1.8 x 10-3 for both phases.

scholarly journals Synthesis of NiMoO4/3D-rGO Nanocomposite in Alkaline Environments for Supercapacitor Electrodes

Crystals ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 31 ◽  
Author(s):  
Shahrzad Arshadi Rastabi ◽  
Rasoul Sarraf Mamoory ◽  
Fatemeh Dabir ◽  
Nicklas Blomquist ◽  
Manisha Phadatare ◽  
...  
Keyword(s):  
Synergistic Effects ◽  
Ammonia Solution ◽  
Precipitation Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
New Methods ◽  
Alkaline Environments ◽  
Pseudocapacitive Behavior ◽  
Ammonia Addition ◽  
A New Technique

Although Graphene oxide (GO)-based materials is known as a favorable candidate for supercapacitors, its conductivity needs to be increased. Therefore, this study aimed to investigate the performance of GO-based supercapicitor with new methods. In this work, an ammonia solution has been used to remove the oxygen functional groups of GO. In addition, a facile precipitation method was performed to synthesis a NiMoO4/3D-rGO electrode with purpose of using synergistic effects of rGO conductivity properties as well as NiMoO4 pseudocapacitive behavior. The phase structure, chemical bands and morphology of the synthesized powders were investigated by X-ray diffraction (XRD), Raman spectroscopy, and field emission secondary electron microscopy (FE-SEM). The electrochemical results showed that the NiMoO4/3D-rGO(II) electrode, where ammonia has been used during the synthesis, has a capacitive performance of 932 Fg−1. This is higher capacitance than NiMoO4/3D-rGO(I) without using ammonia. Furthermore, the NiMoO4/3D-rGO(II) electrode exhibited a power density of up to 17.5 kW kg−1 and an energy density of 32.36 Wh kg−1. These results showed that ammonia addition has increased the conductivity of rGO sheets, and thus it can be suggested as a new technique to improve the capacitance.

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