The Characterisation of Electrodeposited MoS2 Thin Films on a Foam-Based Electrode for Hydrogen Evolution

Molybdenum sulphide is an emerging precious-metal-free catalyst for cathodic water splitting. As its active sites catalyse the Volmer hydrogen adsorption step, it is particularly active in acidic media. This study focused on the electrochemical deposition of MoS2 on copper foam electrodes and the characterisation of their electrocatalytic properties. In addition, the electrodeposition was modified by adding a reducing agent—sodium hypophosphite—to the electrolyte. To reveal the role of hypophosphite, X-ray photoelectron spectroscopy (XPS) analysis was carried out in addition to scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). MoS2 films, electrodeposited at various charges passed through the cell (catalyst loadings), were tested for their catalytic activity towards hydrogen evolution in 0.5 M H2SO4. Polarisation curves and Tafel slope analysis revealed that the electrodeposited MoS2 films are highly active. Namely, Tafel slopes fell within the 40–50 mV dec−1 range. The behaviour of as-deposited films was also evaluated by electrochemical impedance spectroscopy over a wide overpotential range (0 to −0.3 V), and two clear time constants were distinguished. Through equivalent electrical circuit analysis, the experimental data were fitted to the appropriate model, and the obtained values of the circuit components were examined as a function of overpotential. It was found that the addition of NaH2PO2 into the electrodeposition solution affects the intrinsic activity of the material. Finally, a method is proposed to approximate the number of active sites from impedance data.

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Amorphous Ni x Co y P-supported TiO2 nanotube arrays as an efficient hydrogen evolution reaction electrocatalyst in acidic solution

Beilstein Journal of Nanotechnology ◽

10.3762/bjnano.10.6 ◽

2019 ◽

Vol 10 ◽

pp. 62-70 ◽

Cited By ~ 5

Author(s):

Yong Li ◽

Peng Yang ◽

Bin Wang ◽

Zhongqing Liu

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Hydrogen Evolution ◽

Hydrogen Evolution Reaction ◽

Photoelectron Spectroscopy ◽

Electrochemical Impedance ◽

Nanotube Arrays ◽

Active Surface Area ◽

X Ray ◽

Transmission Electron

Bimetallic phosphides have been attracting increasing attention due to their synergistic effect for improving the hydrogen evolution reaction as compared to monometallic phosphides. In this work, NiCoP modified hybrid electrodes were fabricated by a one-step electrodeposition process with TiO2 nanotube arrays (TNAs) as a carrier. X-ray diffraction, transmission electron microscopy, UV–vis diffuse reflection spectroscopy, X-ray photoelectron spectroscopy and scanning transmission electron microscopy/energy-dispersive X-ray spectroscopy were used to characterize the physiochemical properties of the samples. The electrochemical performance was investigated by cyclic voltammetry, linear sweep voltammetry, and electrochemical impedance spectroscopy. We show that after incorporating Co into Ni–P, the resulting Ni x Co y P/TNAs present enhanced electrocatalytic activity due to the improved electron transfer and increased electrochemically active surface area (ECSA). In 0.5 mol L−1 H2SO4 electrolyte, the Ni x Co y P/TNAs (x = 3.84, y = 0.78) demonstrated an ECSA value of 52.1 mF cm−2, which is 3.8 times that of Ni–P/TNAs (13.7 mF cm−2). In a two-electrode system with a Pt sheet as the anode, the Ni x Co y P/TNAs presented a bath voltage of 1.92 V at 100 mA cm−2, which is an improvment of 79% over that of 1.07 V at 10 mA cm−2.

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Fabrication of Hybrid Catalyst ZnO Nanorod/α-Fe2O3 Composites for Hydrogen Evolution Reaction

Crystals ◽

10.3390/cryst10050356 ◽

2020 ◽

Vol 10 (5) ◽

pp. 356

Author(s):

Kasimayan Uma ◽

Elavarasan Muniranthinam ◽

Siewhui Chong ◽

Thomas C.-K Yang ◽

Ja-Hon Lin

Keyword(s):

Hydrogen Evolution ◽

Hydrogen Evolution Reaction ◽

Photoelectron Spectroscopy ◽

Electrochemical Impedance ◽

Nickel Foam ◽

Zno Nanorods ◽

Synergetic Effect ◽

Zno Nanorod ◽

Fe2o3 Nanoparticles ◽

X Ray

This report presents the synthesis of ZnO nanorod/α-Fe2O3 composites by the hydrothermal method with different weight percentages of α-Fe2O3 nanoparticles. The as-synthesized nanorod composites were characterized by different techniques, such as X-ray diffraction (XRD), Fourier transform-infrared (FT-IR), field emission scanning electron microscopy (FE-SEM), electrochemical impedance spectroscopy (EIS), and X-ray photoelectron spectroscopy (XPS). From our results, it was found that the ZnO/α-Fe2O3 (3 wt%) nanorod composites exhibit a higher hydrogen evolution reaction (HER) activity when compared to other composites. The synergetic effect between ZnO and (3 wt%) of α-Fe2O3 nanocomposites resulted in a low onset potential of −125 mV, which can effectively produce more H2 than pure ZnO. The H2 production rate over the composite of ZnO/α-Fe2O3 (3 wt%) clearly shows a significant improvement in the photocatalytic activity in the heterojunction of the ZnO nanorods and α-Fe2O3 nanoparticles on nickel foam.

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WS2–WC–WO3 nano-hollow spheres as an efficient and durable catalyst for hydrogen evolution reaction

Nano Convergence ◽

10.1186/s40580-021-00278-3 ◽

2021 ◽

Vol 8 (1) ◽

Author(s):

Tuan Van Nguyen ◽

Ha Huu Do ◽

Mahider Tekalgne ◽

Quyet Van Le ◽

Thang Phan Nguyen ◽

...

Keyword(s):

Transition Metal ◽

Hydrogen Evolution ◽

Hydrogen Evolution Reaction ◽

Transition Metal Oxides ◽

Photoelectron Spectroscopy ◽

Active Sites ◽

Low Cost ◽

Hollow Spheres ◽

Efficient Catalyst ◽

X Ray

AbstractTransition metal dichalcogenides (TMDs), transition metal carbides (TMCs), and transition metal oxides (TMOs) have been widely investigated for electrocatalytic applications owing to their abundant active sites, high stability, good conductivity, and various other fascinating properties. Therefore, the synthesis of composites of TMDs, TMCs, and TMOs is a new avenue for the preparation of efficient electrocatalysts. Herein, we propose a novel low-cost and facile method to prepare TMD–TMC–TMO nano-hollow spheres (WS2–WC–WO3 NH) as an efficient catalyst for the hydrogen evolution reaction (HER). The crystallinity, morphology, chemical bonding, and composition of the composite material were comprehensively investigated using X-ray diffraction, Raman spectroscopy, field emission scanning electron microscopy, and X-ray photoelectron spectroscopy. The results confirmed the successful synthesis of the WS2–WC–WO3 NH spheres. Interestingly, the presence of nitrogen significantly enhanced the electrical conductivity of the hybrid material, facilitating electron transfer during the catalytic process. As a result, the WS2–WC–WO3 NH hybrid exhibited better HER performance than the pure WS2 nanoflowers, which can be attributed to the synergistic effect of the W–S, W–C, and W–O bonding in the composite. Remarkably, the Tafel slope of the WS2–WC–WO3 NH spheres was 59 mV dec−1, which is significantly lower than that of the pure WS2 NFs (82 mV dec−1). The results also confirmed the unprecedented stability and superior electrocatalytic performance of the WS2–WC–WO3 NH spheres toward the HER, which opens new avenues for the preparation of low-cost and highly effective materials for energy conversion and storage applications.

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Boosting pH-Universal Hydrogen Evolution of FeP/CC by Anchoring Trace Platinum

Crystals ◽

10.3390/cryst12010037 ◽

2021 ◽

Vol 12 (1) ◽

pp. 37

Author(s):

Chuancang Zhou ◽

Feipeng Zhang ◽

Hongyu Wu

Keyword(s):

Hydrogen Evolution ◽

Photoelectron Spectroscopy ◽

Electrochemical Impedance ◽

Pt Nanoparticles ◽

Interface Energy ◽

Catalytic Performance ◽

Carbon Cloth ◽

Electro Deposition ◽

X Ray ◽

Transition Metal Phosphides

To improve the electrocatalytic properties for hydrogen evolution reactions, strategies need to be adopted, such as increasing specific surface area and active site, as well as decreasing interface energy. Herein, we report the preparation of FeP on carbon cloth using a two-step process of hydrothermal and phosphating. Otherwise, to utilize the excellent catalytic performance of Pt and decrease consumption of Pt, the hyperdispersed Pt nanoparticles for the sake of modifying transition-metal phosphides film were designed and fabricated. Finally, 3D FeP-Pt/CC was successfully prepared by means of electro-deposition using three electrodes. The crystalline structure, surface morphology and elemental composition of the synthesized samples have been investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDS). The XRD results show that the as-prepared products are of orthorhombic FeP structure, and EDS results indicate that there exist Pt elements in 3D FeP-Pt/CC. The electrocatalytic performances were evaluated by, such as linear scan voltammetry, tafel plots and electrochemical impedance spectroscopy on electrochemical workstations. These results show that the FeP-Pt/CC exhibit a current density of 10 mA·cm−2 at an over-potential of 58 mV for HER in 0.5 M H2SO4, which is very close to the values of 20%Pt/C which was previously reported. FeP-Pt/CC has excellent durability.

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MoS2-Carbon Inter-overlapped Structures as Effective Electrocatalysts for the Hydrogen Evolution Reaction

Nanomaterials ◽

10.3390/nano10071389 ◽

2020 ◽

Vol 10 (7) ◽

pp. 1389

Author(s):

Po-Chia Huang ◽

Chia-Ling Wu ◽

Sanjaya Brahma ◽

Muhammad Omar Shaikh ◽

Jow-Lay Huang ◽

...

Keyword(s):

Hydrogen Evolution ◽

Hydrogen Evolution Reaction ◽

Photoelectron Spectroscopy ◽

Active Sites ◽

Hydrogen Generation ◽

Interlayer Spacing ◽

Monolayer Mos2 ◽

X Ray Diffraction ◽

X Ray ◽

Transmission Electron

The ability to generate hydrogen in an economic and sustainable manner is critical to the realization of a future hydrogen economy. Electrocatalytic water splitting into molecular hydrogen using the hydrogen evolution reaction (HER) provides a viable option for hydrogen generation. Consequently, advanced non-precious metal based electrocatalysts that promote HER and reduce the overpotential are being widely researched. Here, we report on the development of MoS2-carbon inter-overlapped structures and their applicability for enhancing electrocatalytic HER. These structures were synthesized by a facile hot-injection method using ammonium tetrathiomolybdate ((NH4)2MoS4) as the precursor and oleylamine (OLA) as the solvent, followed by a carbonization step. During the synthesis protocol, OLA not only plays the role of a reacting solvent but also acts as an intercalating agent which enlarges the interlayer spacing of MoS2 to form OLA-protected monolayer MoS2. After the carbonization step, the crystallinity improves substantially, and OLA can be completely converted into carbon, thus forming an inter-overlapped superstructure, as characterized in detail using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). A Tafel slope of 118 mV/dec is obtained for the monolayer MoS2-carbon superstructure, which shows a significant improvement, as compared to the 202 mV/dec observed for OLA-protected monolayer MoS2. The enhanced HER performance is attributed to the improved conductivity along the c-axis due to the presence of carbon and the abundance of active sites due to the interlayer expansion of the monolayer MoS2 by OLA.

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Ternary Composite of Molybdenum Disulfide-Graphene Oxide-Polyaniline for Supercapacitor

Journal of The Electrochemical Society ◽

10.1149/1945-7111/ac3f1e ◽

2021 ◽

Author(s):

Ke Qu ◽

Yuqi Bai ◽

Miao Deng

Keyword(s):

Graphene Oxide ◽

Molybdenum Disulfide ◽

Photoelectron Spectroscopy ◽

Electrochemical Impedance ◽

Light Emitting Diode ◽

Rate Capability ◽

Energy Storage And Conversion ◽

Carbon Paper ◽

Power Sources ◽

X Ray

Abstract The ever-increasing need for small and lightweight power sources for use in portable or wearable electronic devices has spurred the development of supercapacitors as a promising energy storage and conversion system. In this work, a simple, facile and easy-to-practice method has been developed to employ carbon paper (CP) as the support to coat molybdenum disulfide (MoS2) and graphene oxide (GO), followed by electrodeposition of polyaniline (PANI) to render CP/MoS2-GO-PANI. The preparation parameters, such as amounts of MoS2, GO and number of aniline electropolymerization cycles, have been optimized to render CP/MoS2-GO-PANI the best capacitive performance. The as-prepared optimal CP/MoS2-GO-PANI is characterized by X-ray powder diffraction, scanning electron microscopy, energy-dispersive spectroscopy, and X-ray photoelectron spectroscopy. The supercapacitive properties of CP/MoS2-GO-PANI as an electrode have been evaluated electrochemically via cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy testing. CP/MoS2-GO-PANI delivers a specific capacitance of 255.1 F/g at 1.0 A/g and exhibits excellent rate capability under larger current densities. Moreover, a symmetrical supercapacitor is assembled and three are connected in series to power a light-emitting diode for ~15 minutes, demonstrating the promising application potential of CP/MoS2-GO-PANI-based supercapacitor.

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Organosilane-functionalization of nanostructured indium tin oxide films

Interface Focus ◽

10.1098/rsfs.2016.0056 ◽

2016 ◽

Vol 6 (6) ◽

pp. 20160056 ◽

Cited By ~ 10

Author(s):

R. Pruna ◽

F. Palacio ◽

M. Martínez ◽

O. Blázquez ◽

S. Hernández ◽

...

Keyword(s):

Surface Area ◽

Indium Tin Oxide ◽

Photoelectron Spectroscopy ◽

Electrochemical Impedance ◽

Annealing Treatment ◽

Electrochemical Analysis ◽

Cyclic Voltammograms ◽

X Ray ◽

Chip Technology ◽

Significant Difference

Fabrication and organosilane-functionalization and characterization of nanostructured ITO electrodes are reported. Nanostructured ITO electrodes were obtained by electron beam evaporation, and a subsequent annealing treatment was selectively performed to modify their crystalline state. An increase in geometrical surface area in comparison with thin-film electrodes area was observed by atomic force microscopy, implying higher electroactive surface area for nanostructured ITO electrodes and thus higher detection levels. To investigate the increase in detectability, chemical organosilane-functionalization of nanostructured ITO electrodes was performed. The formation of 3-glycidoxypropyltrimethoxysilane (GOPTS) layers was detected by X-ray photoelectron spectroscopy. As an indirect method to confirm the presence of organosilane molecules on the ITO substrates, cyclic voltammetry and electrochemical impedance spectroscopy (EIS) were also carried out. Cyclic voltammograms of functionalized ITO electrodes presented lower reduction-oxidation peak currents compared with non-functionalized ITO electrodes. These results demonstrate the presence of the epoxysilane coating on the ITO surface. EIS showed that organosilane-functionalized electrodes present higher polarization resistance, acting as an electronic barrier for the electron transfer between the conductive solution and the ITO electrode. The results of these electrochemical measurements, together with the significant difference in the X-ray spectra between bare ITO and organosilane-functionalized ITO substrates, may point to a new exploitable oxide-based nanostructured material for biosensing applications. As a first step towards sensing, rapid functionalization of such substrates and their application to electrochemical analysis is tested in this work. Interestingly, oxide-based materials are highly integrable with the silicon chip technology, which would permit the easy adaptation of such sensors into lab-on-a-chip configurations, providing benefits such as reduced size and weight to facilitate on-chip integration, and leading to low-cost mass production of microanalysis systems.

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Capping Agent Effect on Pd-Supported Nanoparticles in the Hydrogenation of Furfural

Catalysts ◽

10.3390/catal10010011 ◽

2019 ◽

Vol 10 (1) ◽

pp. 11 ◽

Cited By ~ 3

Author(s):

Shahram Alijani ◽

Sofia Capelli ◽

Stefano Cattaneo ◽

Marco Schiavoni ◽

Claudio Evangelisti ◽

...

Keyword(s):

Photoelectron Spectroscopy ◽

Active Sites ◽

Catalytic Performance ◽

Shielding Effect ◽

Capping Agents ◽

X Ray ◽

Supported Nanoparticles ◽

Liquid Phase Hydrogenation ◽

Diallyldimethylammonium Chloride ◽

Transmission Electron

The catalytic performance of a series of 1 wt % Pd/C catalysts prepared by the sol-immobilization method has been studied in the liquid-phase hydrogenation of furfural. The temperature range studied was 25–75 °C, keeping the H2 pressure constant at 5 bar. The effect of the catalyst preparation using different capping agents containing oxygen or nitrogen groups was assessed. Polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), and poly (diallyldimethylammonium chloride) (PDDA) were chosen. The catalysts were characterized by ultraviolet-visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The characterization data suggest that the different capping agents affected the initial activity of the catalysts by adjusting the available Pd surface sites, without producing a significant change in the Pd particle size. The different activity of the three catalysts followed the trend: PdPVA/C > PdPDDA/C > PdPVP/C. In terms of selectivity to furfuryl alcohol, the opposite trend has been observed: PdPVP/C > PdPDDA/C > PdPVA/C. The different reactivity has been ascribed to the different shielding effect of the three ligands used; they influence the adsorption of the reactant on Pd active sites.

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Nitrogen-Doped Sponge Ni Fibers as Highly Efficient Electrocatalysts for Oxygen Evolution Reaction

Nano-Micro Letters ◽

10.1007/s40820-019-0253-5 ◽

2019 ◽

Vol 11 (1) ◽

Cited By ~ 19

Author(s):

Kaili Zhang ◽

Xinhui Xia ◽

Shengjue Deng ◽

Yu Zhong ◽

Dong Xie ◽

...

Keyword(s):

Oxygen Evolution ◽

Photoelectron Spectroscopy ◽

Oxygen Evolution Reaction ◽

Active Sites ◽

High Performance ◽

Active Phase ◽

X Ray ◽

Highly Active ◽

N Doping ◽

Energy Conversion Devices

Abstract Controllable synthesis of highly active micro/nanostructured metal electrocatalysts for oxygen evolution reaction (OER) is a particularly significant and challenging target. Herein, we report a 3D porous sponge-like Ni material, prepared by a facile hydrothermal method and consisting of cross-linked micro/nanofibers, as an integrated binder-free OER electrocatalyst. To further enhance the electrocatalytic performance, an N-doping strategy is applied to obtain N-doped sponge Ni (N-SN) for the first time, via NH3 annealing. Due to the combination of the unique conductive sponge structure and N doping, the as-obtained N-SN material shows improved conductivity and a higher number of active sites, resulting in enhanced OER performance and excellent stability. Remarkably, N-SN exhibits a low overpotential of 365 mV at 100 mA cm−2 and an extremely small Tafel slope of 33 mV dec−1, as well as superior long-term stability, outperforming unmodified sponge Ni. Importantly, the combination of X-ray photoelectron spectroscopy and near-edge X-ray adsorption fine structure analyses shows that γ-NiOOH is the surface-active phase for OER. Therefore, the combination of conductive sponge structure and N-doping modification opens a new avenue for fabricating new types of high-performance electrodes with application in electrochemical energy conversion devices.

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Surface Analysis, Microstructural Characterization and Local Corrosion Processes in Decarburized SAE 9254 Spring Steel

CORROSION ◽

10.5006/3234 ◽

2019 ◽

Vol 75 (12) ◽

pp. 1474-1486

Author(s):

Jéssica Cristina Costa de Castro Santana ◽

Rejane Maria Pereira da Silva ◽

Renato Altobelli Antunes ◽

Sydney Ferreira Santos

Keyword(s):

Surface Chemistry ◽

Photoelectron Spectroscopy ◽

Electrochemical Impedance ◽

Microstructural Characterization ◽

Spring Steel ◽

Laser Scanning Microscopy ◽

Local Corrosion ◽

Confocal Laser ◽

X Ray ◽

Decarburized Layer

The aim of the present work was to study the surface chemistry, microstructure, and local corrosion processes at the decarburized layer of the SAE 9254 automotive spring steel. The samples were austenitized at 850°C and 900°C, and oil quenched. The microstructure was investigated using confocal laser scanning microscopy and scanning electron microscopy. The surface chemistry was analyzed by x-ray photoelectron spectroscopy. Electrochemical impedance spectroscopy and potentiodynamic polarization were used to assess the global corrosion behavior of the decarburized samples. Scanning electrochemical microscopy was used to evaluate the influence of decarburization on the local corrosion activity. Microstructural characterization and x-ray photoelectron spectroscopy analysis indicate a dependence of the local electrochemical processes with the steel microconstituents and Si oxides in the decarburized layer.

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