Electrodes In Alkaline Solution Research Articles

The Influence of Acetone on the Kinetics of Water Electrolysis Examined at Polycrystalline Pt Electrode in Alkaline Solution

This study investigated the impact of acetone on the electrochemical behavior of polycrystalline platinum electrodes in 0.1 M NaOH solution, with respect to the kinetics of hydrogen and oxygen evolution reactions (HER and OER) and indirectly to the underpotential deposition of hydrogen (UPDH). Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques were employed to analyze these processes for acetone concentrations ranging from 1.0 × 10−6 to 1.0 × 10−3 M. The addition of (CH3)2C=O enhanced the catalytic efficiency of alkaline water splitting, which was believed to be a result of a significant reduction in the surface tension phenomenon (due to mutual interaction of acetone and water molecules), thus considerably facilitating hydrogen bubble detachment from the Pt electrode. Key findings in this work are described with respect to facilitation of both the HER and the OER reactions’ kinetics by the presence of acetone (also undergoing Pt electroreduction over the potential range for UPDH) in the working solution, without an electrode surface poisoning effect. The latter implies significant opportunities for traces of organic additives into alkaline electrolyte to improve the industrial alkaline water electrolysis process.

Smooth nickel - a suitable anodic material in new alkaline fuel cells sulphite/oxygen

<p>The anodic oxidation of sulphite ions was studied by voltammetric techniques on a nickel electrode in alkaline solution at various concentration of sulphite and polarization rate. The kinetic parameters of the electrode process have been determined using Tafel plots method and a mechanism of the electrochemical oxidation reaction of sulphite has been proposed. Current density, potential range of sulphite electro-oxidation and transformation degree of sulphite ions in the test solutions have been obtained by chronoamperometry and chronocoulometry. The sulphite oxidation mechanism on nickel electrode has been sustained by electrochemical impedance spectroscopy.</p>

Highly selective electrocatalytic alkynol semi-hydrogenation for continuous production of alkenols

Alkynols semi-hydrogenation is a critical industrial process as the product, alkenols, have extensive applications in chemistry and life sciences. However, this class of reactions is plagued by the use of high-pressure hydrogen, Pd-based catalysts, and low efficiency of the contemporary thermocatalytic process. Here, we report an electrocatalytic approach for selectively hydrogenating alkynols to alkenols under ambient conditions. For representative 2-methyl-3-butene-2-ol, Cu nanoarrays derived electrochemically from CuO, achieve a high partial current density of 750 mA cm−2 and specific selectivity of 97% at −0.88 V vs. reversible hydrogen electrode in alkaline solution. Even in a large two-electrode flow electrolyser, the Cu nanoarrays deliver a single-pass alkynol conversion of 93% with continuous production of 2-methyl-3-butene-2-ol at a rate of ~169 g gCu−1 h−1. Theoretical and in situ electrochemical infrared investigations reveal that the semi-hydrogenation performance is enhanced by exothermic alkynol adsorption and alkenol desorption on the Cu surfaces. Furthermore, this electrocatalytic semi-hydrogenation strategy is shown to be applicable to a variety of alkynol substrates.

The correlation of the nickel (1 1 1) facet with the hydrogen evolution performance of Ni electrodes in alkaline solutions

Understanding the structural transformation and degradation mechanism of nickel (Ni) electrodes is beneficial for designing long-lasting and efficient hydrogen evolution reaction (HER) electrodes. Herein, the effects of applied current density and electrolysis time on the HER performance of Ni electrodes were systematically studied in alkaline solutions. After serving as a HER electrode, the intensity of XRD diffraction peak of the Ni (1 1 1) facet increased and the HER performance of the Ni electrode decreased. By reversing the applied current at the used Ni electrode, the intensity of XRD diffraction peak of the Ni (1 1 1) facet decreased, as well as the HER performance increased. Combing the surface change and the density functional theory (DFT) analysis, the HER performance of the Ni electrode was related to the intensity of Ni (1 1 1) facet that can be tuned by controlling hydrogen concentration at surface of Ni electrodes. Overall, this work reveals the relationships between the Ni (1 1 1) facet with its HER performance in alkaline solutions, offering insights into diagnosing and healing approaches for Ni-based HER electrodes.

Electrochemical Nitrate Reduction to Ammonia on Polycrystalline Copper Electrodes in Alkaline Solutions

Ammonia has widely utilized as the raw material of fertilizer and feeds in fuel cells and hydrogen storage materials (Orens. S, Proc. Natl. Acad. Sci. U.S.A. 2021, 118 (49)). In general, the Haber-Bosch process has supplied the mass production of ammonia (N2 + H2 → 2NH3). However, this chemical process requires high-temperature and high-pressure conditions to cleave the triple N2 and produces undesired CO2 gas, as CH4 is added for H2 generation. It is attractive to yield ammonia in milder conditions and more cost-effective methods. In addition, the usage of waste and eco-poisoned species, which is inevitably produced, is valuable as the reactant. For this purpose, nitrate (NO3 -) conversion using electrochemical methods has drawn attention. Nitrate has a high solubility in aqueous media and better reactivity than N2 gas at ambient temperature and atmospheric conditions. Nonetheless, the nitrate reduction undergoes multiple electron-transfer processes (NO3 - + 8e- + 9H+ → NH3 + 3H2O), causing low ammonia selectivity competing against byproducts such as hydrogen, nitrogen oxides, and hydroxylamine.Here, I show critical factors determining the conversion selectivity of nitrate using Cu catalysts. I prepared three Cu foils treated by different surface cleaning processes. Surface morphology and roughness of Cu relying on the surface treatments significantly altered the conversion efficiency. In particular, nitric oxide (NO) was a pivotal intermediate to determine the final products, which was sensitive to the Cu surface condition. I will discuss details of the electrochemical nitrate reduction process observed by in-situ and ex-situ gas and spectroscopic analyses and correlate the conversion efficiency with the surface conditions of Cu foils. Figure 1

Ni3P-Ni heterostructure electrocatalyst for alkaline hydrogen evolution

Highly active and stable electrocatalysts at low cost for hydrogen evolution reaction are essential for large scale hydrogen production. The Ni3P-Ni heterostructure confined in 3D networks of carbon nanotube (CNT) has been successfully prepared as the hydrogen evolution reaction (HER) electrode. The morphology and phase composition of Ni3P-Ni heterostructure are tunable by varying the acid pickling time. The Ni3P-Ni/CNT composite electrode with optimized Ni:Ni3P ratio of 22.29 wt% demonstrate high catalytic activity and excellent stability for HER. It demonstrates a comparable HER activity to the standard Pt electrode in alkaline solution, i.e., overpotentials of 116 vs 67 mV at 10 mA·cm−2 and Tafel slops of 59 vs 37 mV·dec−1. No degradation is observed after 1000 cyclic voltammetry (CV) cycles or 50 h operation under constant 0.3 V overpotential.

Non-noble metal FeMn and single-walled carbon nanotubes nanocomposites as effective bifunctional electrocatalysts in alkaline media for oxygen/hydrogen revolution reactions

Single-walled carbon nanotubes (SWCNTs) are one of electrochemical materials with excellent electrical properties. Herein, we design the new FeMn x /SWCNTs nanocomposites which are synthesized in one step by the direct current (DC) arc discharge method. The overpotentials of oxygen/hydrogen revolution reactions of FeMn 1 /SWCNTs electrodes in alkaline solution are 190 and 317 mV respectively when the current density reaches 10 mA cm −2 . The synergistic effect between FeMn compounds and single-walled carbon nanotubes can not only increase the active sites of the composites, but also optimize the electronic structure of the composites, thereby significantly improving the OER and HER performance of the materials. This work provides an idea that the composites of SWCNTs and bimetallic hybrids have excellent electrocatalytic performance.

The Correlation of the Nickel (111) Facet with the Hydrogen Evolution Performance of Ni Electrodes in Alkaline Solutions

The Correlation of the Nickel (111) Facet with the Hydrogen Evolution Performance of Ni Electrodes in Alkaline Solutions

Supercapacitive and Methanol Oxidation Performances of Hierarchical Porous Three-Dimensional Ni/Cuco2o4 Core-Shell Composites as a Binder-Free Electrodes in Alkaline Solution

Supercapacitive and Methanol Oxidation Performances of Hierarchical Porous Three-Dimensional Ni/Cuco2o4 Core-Shell Composites as a Binder-Free Electrodes in Alkaline Solution

Potential and time dependent broad band sum frequency generation spectroscopic study on electrochemical oxidation of adsorbed CO on Pt(1 1 1) electrode surface in pre-peak region in alkaline solution

• SFG spectra of adsorbed CO on Pt(111) showed on-top peak in HClO 4 and NaOH solutions. • The on-top SFG peak totally disappeared in pre-peak region in NaOH solution. • The on-top SFG peak totally disappeared in the main peak region in HClO 4 solution. • Adsorbed CO was oxidized by reacting with OH − in solution via Eley-Rideal mechanism. • SFG inactive adsorbed CO was oxidized in the main peak region in NaOH solution. In situ broad band sum frequency generation (SFG) spectroscopy was applied to clarify the oxidation mechanism of adsorbed CO on Pt(1 1 1) electrode in alkaline solution in comparison with that in acidic solution. A single SFG peak due to CO adsorbed on-top site of Pt(1 1 1) was observed in the region of 1950 – 2150 cm −1 . While oxidation of adsorbed CO proceeded in a nucleation-growth mode via Langmuir–Hinshelwood (L-H) mechanism by reacting with adsorbed OH in the main peak region in 0.1 M HClO 4 solution, adsorbed CO was oxidized in a random oxidation model via Eley-Rideal (E-R) mechanism by reacting with OH − in the solution in the pre-peak region in 0.1 M NaOH solution. The main anodic peak was still observed even after the SFG peak due to on-top CO was totally disappeared by anodic oxidation in the pre-peak region, showing there existed SFG inactive adsorbed CO, although its structure was not clear.

Theory of Electrochemical Proton-Coupled Electron Transfer in Diabatic Vibronic Representation: Application to Proton Discharge on Metal Electrodes in Alkaline Solution

Proton discharge on a metal electrode is an important step in a wide range of electrocatalytic processes. In this proton-coupled electron transfer (PCET) reaction, also denoted the Volmer reaction,...

P-doped cobalt carbonate hydroxide@NiMoO4 double-shelled hierarchical nanoarrays anchored on nickel foam as a bi-functional electrode for energy storage and conversion

The rational structure design and controllable surface modification of electrode materials plays a decisive role in constructing high performance energy storage and conversion devices. Herein, the P-doped cobalt carbonate hydroxide@NiMoO4 (P-CoCH@NiMoO4) nanowires@nanosheets double-shell hierarchical structure is successfully fabricated on nickel foam. The unique nanowire@nanosheet structure with gradient porous distribution and hydrophilic nature can facilitate both the charge and electron transfer based on the synergetic effects with conductive NiMoO4 array. Importantly, the dopant of P element can enrich oxygen vacancies on the surface of CoCH nanowire, thus increase the effective active sites and enhance the electrocatalytic performance. Therefore, when act as the supercapacitor electrode, the bi-functional P-CoCH@NiMoO4/NF material achieves high areal capacitance (5.08 F cm−2 at 2 mA cm−2, 0.75 mAh cm−2) and good cyclic stability (82.7% capacitance retention after 2000 cycles). Meanwhile, when utilize as the hydrogen evolution electrode in alkaline solution, a low overpotential (115 mV at 10 mA cm−2) and Tafel slope (113.5 mV dec−1) can also be achieved.

AgNP-“Zeolite A”/NG as a Novel Nanocatalyst for Methanol Electro-Oxidation in Alkaline Setting

In this research, the glassy carbon electrode was modified by silver nanoparticles zeolite type A composite, hybridized with the nitrogen-doped graphene (AgNP-“zeolite A”/NG). The electrocatalytic oxidation of methanol was investigated at the surface of the modified electrode in alkaline solution using cyclic voltammetry, chronoamperometry and linear sweep voltammetry methods, and followingly, excellent electrocatalytic activity was observed. The structure and morphology of the resulting AgNP-“zeolite A”/NG were characterized by scanning electron microscopy, dynamic light scattering, X-ray diffraction, Fourier transform infrared spectroscopy and Raman spectroscopy techniques. This electrode was found as a good candidate for application in the anode pole of the direct methanol fuel cell. Silver incorporated in this modified electrode played a key role for oxidation of methanol. The results confirmed the adsorption-controlled reaction at the surface of the modified electrode. Also, the effect of some parameters such as pH, scan rate of potential and the concentration of methanol were explored. Moreover, the kinetic parameters such as transfer coefficient (ko) and exchange current (io) were obtained 1.199 × 10−7 and 2.18 × 10−4 A, respectively, for methanol electro-oxidation process by the AgNP-“zeolite A”/NG. The relative standard deviation of ten replicate measurements, performed on a single electrode in 1.5 × 10−4 M of methanol in alkaline setting, was calculated 2.1% too.

Theoretical analysis of mass transfer during anodic dissolution of tungsten rotating disk electrode in alkaline solutions

The mass transfer during the electrochemical dissolution of metals with the participation of electrolyte anions and the formation of stable anionic complex is analyzed by the example of tungsten anodic dissolution in the alkaline solutions. The distributions of ionic concentrations, partial current densities of ions and potential over the solution layer near the anode are determined as a result of numerical solution of the problem. The results of numerical solution are compared to the results of analytical solution and experimental data available from the literature. It is shown that the numerical solution of the problem with regard for migration, convection and concentration dependences of transport properties of solution agrees well with the experimental data. A complex role of ion migration in this process is revealed.

Monitoring of CO Binding Sites on Stepped Pt Single Crystal Electrodes in Alkaline Solutions by in Situ FTIR Spectroscopy.

The site geometry preference of CO binding on stepped Pt single crystals in alkaline solution was investigated by in situ FTIR spectroscopy. The surfaces of the Pt single crystals consisted of different width (111) terraces, interrupted by (110) or (100) monatomic steps. Experiments carried out with CO adsorbed exclusively on the top of the steps revealed that only linearly bonded CO formed on the (110) steps, while two CO binding geometries (linear and bridge) were observed on the (100) steps. On one hand, for CO adsorbed only on the steps, the positions of the bands corresponding to linearly bonded CO were similar, regardless of the density of steps, suggesting the existence of an interaction between COads only along the line of the steps. On the other hand, for full CO coverage, the CO stretching frequencies and the geometry of bound CO were sensitive to the width of the (111) terraces and the step orientations. Consequently, the CO binding sites favored linearly bonded CO for surfaces consisting of shorter (111) terraces and (110) steps. Bridge-bonded CO was favored on surfaces consisting of shorter (111) terraces interrupted by (100) steps. In order to understand the origin of the preference of CO binding sites, the results were compared to the corresponding behavior in acid media, which revealed that, in addition to the effect inherent to the Pt surface, the charge on the metal side in an aqueous environment should be taken into consideration. The analysis suggested that the CO adlayers formed at full coverage in acidic and alkaline media had different structures. On the other hand, the structure of the layer of CO adsorbed only at the steps was independent of pH.

Electrocatalytic oxidation of ethanol and ethylene glycol on bimetallic Ni and Ti nanoparticle-modified indium tin oxide electrode in alkaline solution

Bimetallic Ni and Ti nanoparticle-modified indium tin oxide electrode (Ni–Ti NPs/ITO) were prepared by a two-step ion implantation method, and their electrocatalytic activity toward the oxidation of ethanol and glycol was evaluated. The ion-implantation method is simple, low-cost and environmental friendly without the use of any binder. The Ni–Ti NPs/ITO electrode were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). SEM and AFM showed that the nanoparticles on the Ni–Ti NPs/ITO electrode had a small range of dispersion (10–20 nm) and high dispersion. Electrochemical performances were measured by cyclic voltammetry (CV) and chronoamperometrics. The Ni–Ti NPs/ITO electrode exhibited much higher electrocatalytic activity and stability for ethanol and ethylene glycol oxidation than NiNPs/ITO.

Oxygen reduction reaction on thin-film Ag electrodes in alkaline solution

Thin Ag films with nominal thicknesses from 0.5 to 10 nm deposited on a glassy carbon (GC) substrate were prepared by electron beam evaporation and the oxygen reduction reaction (ORR) on the Ag/GC electrodes in alkaline solution was studied employing the rotating disk electrode (RDE) technique. Transmission electron microscopy (TEM) was used to examine the surface morphology of Ag films and it was found that the average particle size for the thinnest film was about 5.5 nm. The Ag particle size increased with increasing the film thickness and for 5 nm film the silver particles merged to a uniform coating. Electrochemical testing showed that the thin-film Ag electrodes are efficient catalyst for oxygen reduction and peroxide reduction reactions. The electron transfer number was calculated to be slightly lower than four for thinnest Ag film and it was 4 for all the other films. Tafel analysis showed similar slope value for all thin-film Ag electrodes revealing that the rate-determining step does not change with the Ag film thickness. The electro-oxidation of Ag films and Pb underpotential deposition experiments were also conducted. Finally, Ag coatings were electrochemically stripped from the GC electrode to determine the mass of Ag on the substrate surface, which was in good agreement with the calculated value. The 1 nm Ag film showed the best utilisation of silver, as mass and specific activities for ORR were the highest for that coating. Nanostructured Ag electrodes might be promising catalysts for alkaline membrane fuel cells.

Electrochemical properties of Fe2O3/AB based composite electrodes in alkaline solution

To find a suitable material for Fe-air battery anode, Fe2O3 nanoparticles (nm) and microparticles (µm) were used as active materials and Acetylene Black carbon (AB) as additive to prepare Fe2O3/AB composites. The effect of grain size of iron oxide particles and additives on the electrochemical behavior of Fe2O3/AB composite electrodes in alkaline solution have been investigated using cyclic voltammetry (CV), galvanostatic cycling and electrochemical impedance spectroscopy (EIS) measurements. Iron oxide nanoparticles provided better cyclability than iron oxide microparticles. Impedance of electrode increased during cycling but the nm-Fe2O3/AB electrode gave smaller resistance than µm-Fe2O3/AB one. The additives showed strongly effects on the electrochemical behaviors of iron oxide electrodes. The AB additive enhanced the electric conductivity of Fe2O3/AB electrode and thus increased the redox reaction rate of iron oxide while K2S interacted and broke down the passive layer leading to improved cyclability and giving higher capacity for Fe2O3/AB electrodes.

Elucidating mechanisms of oxide growth and surface passivation on zinc thin film electrodes in alkaline solutions using the electrochemical quartz crystal microbalance

We utilized electrochemical quartz crystal microbalance to understand electrochemical passivation of the zinc electrode in alkaline media and subsequent oxide growth and stripping. The formation of native zinc oxide on a near pristine Zn surface upon contact with 1 M KOH electrolyte was observed. The surface was seen to roughen with time. During Zn dissolution, the measured mass-charge ratio corresponded to the removal of ZnO and not merely Zn. The mechanism of passivation was determined to be caused by electrochemical etching to form pores. The etching leads to a build-up of solid ZnO and Zn(OH)2 due to electrochemical reactions on the surfaces of the pores. These reactions functionally close the pores off from the bulk. The cycle of Zn deposition and dissolution develops a porous network, which may be the origin of mossy Zn deposits that plague reversible Zn metal batteries.

Modeling of mass transfer during anodic dissolution of vertical wire tungsten electrode in alkaline solutions

The problem of mass transfer during anodic dissolution of vertical wire tungsten electrode in the alkaline solution under the conditions of natural convection is solved numerically. The concentration dependences of ionic diffusion coefficients, solution density and viscosity are taken into account. The distributions of concentrations, current density and potential over the near-anode layer are determined. The dependence of limiting current on the concentration of alkaline solution is obtained. The role of ion migration in the tungsten dissolution is shown. The results are compared with the experimental data.