Parameters Of Hydrogen Evolution Reaction Research Articles

Correct determination of the hydrogen evolution reaction parameters at Ni foam electrode modified by electrodeposited Ni-Sn alloy layer

The example of the procedure for the correct determination of the parameters of hydrogen evolution reaction (HER), the exchange current density (jo) and relaxation time (to) for intermediate (adsorbed hydrogen, Hads) adsorption at modified porous Ni-based electrode are presented in this work. Such a procedure is applicable for the HER at all electrode materials. The value of jo was obtained from the intercept at h = 0 mV from the h vs. log (Rct-1) dependence (h - overpotential), while the value of to was obtained from the intercept at h = 0 mV from the logt vs. h dependence. It was shown that for the correct determination of jo and to, it is necessary to correct applied h for the jRs drop, by recording current density (j) for applied h and correcting it for jRs

MoS2−x/GCD-MoS2−x nanostructures for tuning the overpotential of Volmer-Heyrovsky reaction of electrocatalytic hydrogen evolution

MoS2 nanostructures are famous electrocatalysts in hydrogen evolution reaction (HER). The presence of graphene was already reported to boost the electrocatalytic activity of MoS2. This work reports the influence of Sulphur deficiency and economically synthesizable green carbon dot (GCD) incorporation into hydrothermally synthesized MoS2 nanostructures on the electrocatalytic activity of HER. All as-synthesized nanocatalysts are Sulphur deficient (MoS2−x and GCD-MoS2−x) and exhibited superior HER activity as compared to commercial MoS2. MoS2−x 220 exhibited a Tafel slope of 43 mV/Dec indicates the reaction mechanism as Volmer-Heyrovsky with Heyrovsky as rate determining step. Best electrocatalytic parameters are observed for the same catalyst with overpotential: 247 mV at 10 mA/cm2, Turnover frequency: 0.42 s−1, double layer capacitance: 23.8 mF/cm2 and electrochemically active surface area: 595/cm2. The obtained preferable HER parameters suggest that Sulphur deficiency and incorporation of GCD in MoS2 are playing a vital role in HER electrocatalysis.

Recent Advances on Bimetallic Transition Metal Phosphides for Enhanced Hydrogen Evolution Reaction

AbstractDeveloping excellent electrocatalysts to replace noble metal catalysts and improve hydrogen production via water splitting is a daunting task. Bimetallic transition metal phosphides (TMPs) display improved performance than monometallic transition metal phosphides due to their synergistic effects. Moreover, research has proven that supporting them on conductive substrates can further enhance their electrochemical performance. Recently, metal‐organic frameworks (MOFs) are incorporated into bimetallic TMPs for enhanced performance. This review starts with a synopsis of the reaction mechanisms and performance parameters of hydrogen evolution reaction (HER) electrocatalysts. Moreover, the strategies for enhancing the performance of bimetallic TMPs and improving the hydrophilicity of TMPs are also discussed. In conclusion, the challenges and perspectives of bimetallic transition metal phosphides are discussed. This review analyses the extensive progress in this research domain and proffers insights that can aptly guide the future development of more excellent TMPs and other transition metal electrocatalysts for enhanced hydrogen evolution reaction.

Recent Progress in Layered Double Hydroxide‐Based Electrocatalyst for Hydrogen Evolution Reaction

AbstractHydrogen energy is considered as promising renewable resource and desirable alternative to fossil fuels for future energy supply. Hydrogen production from electrocatalytic water splitting is a green and key approach for hydrogen energy development and application, and the effective electrocatalysts for hydrogen evolution reaction (HER) with low cost is the focus of ongoing research. Currently, noble metals‐based materials are the most effective and durable electrocatalysts for HER, while the high cost and low reserves greatly hinder their commercial applications. Recently, layered double hydroxides (LDHs) with interesting properties, such as the tunability of metal cation and interlayer anions, the adjustability of the thickness and spacing for the layers, low cost, and memory effect, have emerged as excellent electrocatalysts to enhance HER performance. Herein, the principal mechanisms and some key parameters for HER are firstly briefly introduced. Afterwards, the structural features and characteristics of LDHs are provided, and the typical design strategies to improve the HER activity of binary and ternary LDHs‐based catalysts are analyzed and discussed. In addition, the relationship between the morphology, structure, composition and involved electronic effects are focused and emphasized. Finally, the challenges and prospects of LDHs‐based catalysts for enhanced HER performance are proposed.

Effect of Hydrogen Pressure on the Intrinsic Kinetics of Hydrogen Evolution Reaction at Pt(111) Electrode

Many kinetic studies on hydrogen evolution reaction (HER) were done in N2 saturated solutions in order to avoid possible H2 leakage, which results in a variation of H2 concentration at the electrode/electrolyte interface (). It will induce the drift of equilibrium potential (Eeq) and applied activation overpotential (η act) for HER. Consequently, it may result in errors for estimating the kinetic parameters for HER. By taking HER at Pt(111) under RDE configuration as a model reaction, quantitative relation among and the reaction current density (j) is established based on the mass transport equations. From the j–η act plots, our results reveal that i) with the increase of HER current, the equivalent increases, which accompanies with a drift of thermodynamic equilibrium potential (Eeq) for HER decreases; ii) when η act is negative of −50 mV, the j–η act plot for HER is the same in N2 and H2 saturated solution, with a slope of 30 mV Dec−1; Our results suggest that HER activity should be compared in solutions with the same composition and at the same activation overpotential instead of at the same applied potential. Proper experimental methods for post data analysis are proposed in order to derive the intrinsic HER kinetics.

Edgeless porous carbon coating for durable and powerful lead-carbon batteries

A systematic study considering the microstructural effect of carbon materials on the electrochemical or electrocatalytic performance is essential for developing carbon electrode materials of electric vehicles and smart grids that require durable and robust energy supply. In this study, the edge sites within activated carbons (ACs) were physically modified via thermal treatment to clarify the relationship between the edge density and hydrogen evolution reaction (HER). Moreover, their dominant contribution to the electrochemical performance of lead-carbon batteries was demonstrated. The ACs exhibited decreased defect density and enhanced crystallinity due to the merger of micro-domains during a high-temperature thermal treatment (HTT). In contrast to the specific surface area, the edge area of the ACs, which was quantified via temperature programmed desorption up to 1800 °C, decreased significantly with increasing HTT temperature. We have confirmed a close relationship between the edge densities and HER parameters. The lead-carbon battery unit cell employing HTT1600 with the lowest edge ratio (0.81%) exhibited a higher charging efficiency, higher cycling stability, and lower water loss than the cell employing pristine AC with a high edge ratio (8.42%). The edge ratio of carbon materials can be considered an important parameter in designing electrode materials for electrochemical energy storage.

Effect of temperature on process and kinetic parameters of the hydrogen evolution reaction of X80 under CP

Purpose This paper aims to study the effect of temperature on the process and kinetic parameters of the hydrogen evolution reaction of X80 under cathodic protection (CP) in 3.5% NaCl solution. Design/methodology/approach Potentiodynamic polarization combined with the hydrogen permeation test is used to analyze the hydrogen evolution reaction (HER) process and the rate-determining step for which is diagnosed through the electrochemical impedance spectrum method. Then, the influence of temperature on kinetic parameters of HER can be known from the results obtained by using the Iver-Pickering-Zamenzadeh model for data analysis. Findings The results show that the HER proceeds through Volmer–Tafel route with the Volmer reaction acting as the rate-controlling step; Increasing temperature gives a higher activity of the HER on X80, it also accelerates the hydrogen desorption and diffusion of hydrogen into the metal. Originality/value There exist few studies on the topic of how temperature affects the HER process. It is imperative to conduct a relevant study to give some instruction in cathodic protection system design and this paper fulfills this need.

Surface state and proton adsorption phenomena on CoRu-based materials during hydrogen evolution reaction in acid conditions

The electrocatalytic activity for hydrogen evolution reaction (HER) of cobalt-ruthenium based nanomaterials (Co80Ru20 and Co80Ru15Pt5) synthesized by high energy mechanical milling was studied in acid medium. The synthesized materials were immersed in a carbon paste electrode matrix (20 wt.%). X-ray diffraction, scanning electron microscopy and transmission electron microscopy were used to characterize the synthesized powders. The composition of the nanomaterials was established by means of energy dispersive spectroscopy (EDS). SEM and TEM analysis showed the formation of agglomerates of 1–5 μm, constituted by particles of ca. 20 nm. The electrocatalytic activity of the prepared materials was evaluated in 0.5 M H2SO4 at 25 °C using linear sweep voltammetry and electrochemical impedance spectroscopy (EIS) techniques. EIS diagrams were obtained in a frequency range from 100 kHz to 10 mHz at selected potentials. Nyquist diagrams showed the presence of two semicircles. The kinetic parameters for HER obtained from analysis of polarization and impedance data showed that both materials exhibit good performance toward HER. According to the electrochemical parameters, the material with the best performance was Co80Ru15Pt5.

Controlling the Morphology and Efficiency of Nanostructured Molybdenum Nitride Electrocatalysts for the Hydrogen Evolution Reaction

AbstractAmong catalysts based on non‐noble metals, Mo‐based materials are important for hydrogen evolution because of their low cost, good conductivity, and catalytic efficiency. This study demonstrates a facile two‐step synthesis of Mo2N nanostructures assembled from 5–8 nm particles with graphitic carbon nitride as the nitrogen source. These Mo2N nanostructures of various morphologies (hexagons, triangles, and nanowires) show a very high activity and stability in acidic media during water electrolysis. Their nanostructures were characterized by using powder XRD, electron microscopy, N2 gas adsorption analysis, and X‐ray photoelectron spectroscopy. Hydrogen evolution reaction parameters, which include the Tafel slope, charge transfer resistance, and stability, were analyzed by using linear sweep voltammetry and electrochemical impedance spectroscopy. Thin hexagonal sheets of Mo2N show the highest apparent electrocatalytic activity (current density of 197 mA cm−2geometric at −400 mV vs. the reversible hydrogen electrode) and excellent stability in an acidic medium with a small onset potential of 90 mV and a Tafel slope of 145 mV decade−1. The lowest Tafel slope was observed for Mo2N nanowires.

Sol–gel synthesis of palladium nanoparticles supported on reduced graphene oxide: an active electrocatalyst for hydrogen evolution reaction

In this work, the synthesis and characterization of palladium nanoparticle-reduced graphene oxide hybrid (Pd–rGO) material is reported. Techniques of X-ray diffraction, transmission electron microscope (TEM), energy-dispersive X-ray, FT-IR spectroscopy, thermogravimetric analysis and cyclic voltammetry were used to characterize the structure and properties of the Pd–rGO. Results demonstrate the effect of Pd on the reduced GO. The average particle size of the Pd nanoparticles supported on rGO obtained from TEM is about 12–18 nm. Moreover, glassy carbon electrode (GCE) modified with palladium nanoparticle–graphene oxide hybrid (Pd–rGO/GCE) was prepared by casting of the Pd–rGO solution on GCE. The electrochemical and catalytic activity of the Pd–rGO/GCE was studied in 0.1 M H2SO4 solution. The Pd–rGO/GCE electrode exhibited remarkable electrocatalytic activity for the hydrogen evolution reaction (HER). At potential more negative than −0.4 V vs. Ag |AgCl |KCl3M, the current is mainly due to hydrogen evolution reaction. Finally, the kinetic parameters of hydrogen evolution reaction are also discussed on the Pd–rGO/GCE.

Kinetics and mechanism of hydrogen evolution reaction on cobalt silicides in alkaline solutions

Cathodic polarisation curves and impedance spectra for cobalt silicides Co2Si and CoSi2 in 0.5–2M KOH at ambient temperature were obtained. It was shown that electrocatalytic activity of both silicides in hydrogen evolution reaction (HER) is higher than that of cobalt. The dependences of equivalent circuit elements on the electrode potential were analysed. The conclusion was made that the atomic hydrogen adsorption on the surface of cobalt silicides is described by the Langmuir isotherm, and hydrogen evolution proceeds through the Volmer–Heyrovsky mechanism (at α1≠α2 for Co2Si and α1=α2 for CoSi2; α1 and α2 are the transfer coefficients for the Volmer and Heyrovsky steps respectively). The Heyrovsky reaction is probably the rate-determining step. The values of the kinetic parameters of HER on Co2Si and CoSi2 in 1M KOH were estimated.

硫酸水溶液中のアルミニウム表面で起こる水素発生反応とその解析

Efforts by trial and error between experimental measurements and theoretical approaches have been made to obtain electrochemical parameters of hydrogen evolution reaction occurred on aluminum in sulfuric acid solution. Polarization curves of aluminum in 0.01, 0.1 and 0.5 mol·dm-3 sulfuric acid solutions with dissolved oxygen-free and stagnant conditions were measured and analyzed by the polarization resistance method. The method reveals that the electrochemical characteristics of hydrogen evolution reaction on aluminum in sulfuric acid solution had the exchanged current density of i0=10-4.5 mA·cm-2 in 0.5 mol·dm-3 sulfuric acid solution, which generally corresponded with published data elsewhere.

Influence of o-fluorophenylbiguanidine on the kinetics of hydrogen evolution reaction on iron, the nature of rate-determining step and hydrogen diffusion through a steel membrane

It is shown, hydrogen evolution reaction (HER) on iron occurs according to Volmer–Tafel mechanism in acidic aqueous chloride solutions with constant ionic strength. Relation between o-fluorophenylbiguanidine (o-FPBG) concentration and the kinetics and the nature of rate-determining step (rds) of hydrogen evolution reaction (HER) on iron in acidic chloride media with constant ionic strength has been established. Kinetic parameters of HER – dE/dlogic, dE/dlogCH+, (dlogic/dlogCH+)E, dη/dlogic, dη/dlogCH+ and (∂logic/∂logCH+)η – have been obtained at different concentrations of o-FPBG and compared with theoretical values appropriate to Volmer–Tafel mechanism. An increase in the o-FPBG concentration provokes sequential change of the rds in the hydrogen evolution reaction according to scheme: slow discharge – slow recombination – slow surface diffusion – slow discharge. It is proved that in the background solutions the slow discharge is followed by chemical recombination, but hydrogen diffusion rate through a steel membrane practically does not depend on the rds nature. Observed phenomena are interpreted from a position of existence of two adsorbed hydrogen forms – subsurface and raised above the surface – and difference in surface coverage by either of them.

Temperature Effect on Hydrogen Evolution Reaction at Au Electrode

The temperature dependence of hydrogen evolution reaction (HER) at a quasi-single crystalline gold electrode in both 0.1 mol/L HClO4 and 0.1 mol/L KOH solutions was investigated by cyclic voltammetry. HER current displays a clear increase with reaction overpotential (η) and temperature from 278–333 K. In 0.1 mol/L HClO4 the Tafel slopes are found to increases slightly with temperature from 118 mV/dec to 146 mV/dec, while in 0.1 mol/L KOH it is ca. 153±15 mV/dec without clear temperature-dependent trend. The apparent activation energy (Ea) for HER at equilibrium potential is ca. 48 and 34 kJ/mol in 0.1 mol/L HClO4 and 0.1 mol/L KOH, respectively. In acid solution, Ea decreases with increase in η, from Ea=37 kJ/mol (η=0.2 V) to 30 kJ/mol (η=0.35 V). In contrast, in 0.1 mol/L KOH, Ea does not show obvious change with η. The pre-exponential factor (A) in 0.1 mol/L HClO4 is ca. 1 order higher than that in 0.1 mol/L KOH. Toward more negative potential, in 0.1 mol/L HClO4 A changes little with potential, while in 0.1 mol/L KOH it displays a monotonic increase with η. The change trends of the potential-dependent kinetic parameters for HER at Au electrode in 0.1 mol/L HClO4 and that in 0.1 mol/L KOH are discussed.

Electrocatalytic evolution of hydrogen on the NiCu/Al2O3/nano-carbon network composite electrode

We present a way to fabricate the NiCu/Al2O3/nano-carbon network (NCN) composite electrode by coelectrodepositing NiCu particles, using a novel conductive alumina/NCN composite material as the support. The morphology, crystalline phases, and compositions are characterized by field-emission scanning electron microscope, energy dispersive X-ray spectroscope, X-ray diffraction, and Raman spectroscopy. The electrocatalytic behaviors of this NiCu/Al2O3/NCN composite material for hydrogen evolution reaction (HER) in alkaline solution are studied by cathodic polarization curves, electrochemical impedance spectroscopy (EIS), and chronoamperometry. The results show that nickel–copper particles are briefly deposited and uniformly distributed over the carbon layer of the conductive ceramics between alumina grains, in the form of a NiCu solid solution with face-centered cubic structure. The NiCu/Al2O3/NCN composite displays a high electrochemical stability in alkaline solution and relatively high electrocatalytic activity for HER due to its relatively high real surface area and high intrinsic electrocatalytic effect of NiCu alloy particles. The associated kinetic parameters of HER are systematically investigated using EIS.

Catalytic enhancement of hydrogen evolution reaction on copper in the presence of benzylamine

Benzylamine catalytic effect on the cathodic hydrogen evolution in acid aqueous solution has been studied on copper electrode. Experimental results obtained by voltammetric techniques emphasize that the presence of benzylamine in 1 M sulfuric acid solution enhances the hydrogen evolution reaction (HER). In such a solution, benzylamine is protonated and exists as benzylammonium cation. Kinetic parameters of HER have been determined, observing a significant increase of the exchange current in the presence of benzylamine. Also, a decrease of the cathodic transfer coefficient has been noticed. Activation energy for HER has been computed on the basis of the Arrhenius plots. In the presence of benzylamine the activation energy was 33.0 kJ mol −1, whereas without benzylamine a greater value was obtained: 94.6 kJ mol −1. The catalytic effect of benzylamine was confirmed by electrochemical impedance spectroscopy. The considerable diminution of the double layer capacity is a valid proof of the strong adsorption of benzylamine at the Cu – sulfuric acid solution interface, while the reduction of the charge transfer resistance is a symptom of the enhancement of HER. Ab initio molecular modeling of benzylammonium ion showed that, due to a high value of the dipole moment, the molecules are oriented in the most favorable position for the charge transfer reaction, i.e., with the protonated amino group facing toward the electrode.

Electrocatalytic evolution of hydrogen on porous alumina/gelcast-derived nano-carbon network composite electrode

We presented a way to fabricate new porous alumina/gelcast-derived nano-carbon network (NCN) composite electrode using gelcasting and reduction-sintering method. The morphology, crystalline phases, and nanostructure of the alumina/NCN electrode were characterized. The electrocatalytic activity of this elelctrode toward hydrogen evolution reaction (HER) in alkaline solutions was investigated. The electrocatalytic activity analyzed by cyclic voltammetry exhibited the onset potential for HER shifted in the positive direction favoring hydrogen generation with lower overpotential on the porous electrode, compared with pure carbon electrode. This behavior was attributed to the high porosity and electrochemical surface area as well as the nanostructure of the electrode that was pyrolyzed nano-carbon networks introduced into the alumina ceramic matrix, which can greatly enhance the electrode electrocatalytic activity toward HER. The associated kinetic parameters of HER were systematically investigated using electrochemical impedance spectroscopy.

In situ activation of cobalt cathodes in alkaline water electrolysis

The hydrogen evolution reaction (HER) on polished pure cobalt cathodes in 30 w/o KOH at 70°C in the presence of dissolved metallic impurities has been investigated in constant current and potential modes combined with the potential-sweep method. Potentiostatic tests show that the cell current decreases with time during the first 1000 s, which is tentatively attributed to the penetration of atomic hydrogen into the metal lattice. The deposition of copper, iron and zinc, observed after several hours' incubation significantly influences the Tafel parameters for HER.