Hydrogen Evolution Current Research Articles

Multi-Group Polymer Coating on Zn Anode for High Overall Conversion Efficiency Photorechargeable Zinc-Ion Batteries.

The solar-driven photorechargeable zinc-ion batteries have emerged as a promising power solution for smart electronic devices and equipment. However, the subpar cyclic stability of the Zn anode remains a significant impediment to their practical application. Herein, poly(diethynylbenzene-1,3,5-triimine-2,4,6-trione) (PDPTT) was designed as a functional polymer coating of Zn. Theoretical calculations demonstrate that the PDPTT coating not only significantly homogenizes the electric field distribution on the Zn surface, but also promotes the ion-accessible surface of Zn. With multiple N and C=O groups exhibiting strong adsorption energies, this polymer coating reduces the nucleation overpotential of Zn, alters the diffusion pathway of Zn2+ at the anode interface, and decreases the corrosion current and hydrogen evolution current. Leveraging these advantages, Zn-PDPTT//Zn-PDPTT exhibits an exceptionally long cycling time (≥4300 h, 1 mA cm-2). Zn-PDPTT//AC zinc-ion hybrid capacitors can withstand 50,000 cycles at 5 A/g. Zn-PDPTT//NVO zinc-ion battery exhibits a faster charge storage rate, higher capacity, and excellent cycling stability. Coupling Zn-PDPTT//NVO with high-performance perovskite solar cells results in a 13.12 % overall conversion efficiency for the photorechargeable zinc-ion battery, showcasing significant value in advancing the efficiency and upgrading conversion of renewable energy utilization.

Multi‐Group Polymer Coating on Zn Anode for High Overall Conversion Efficiency Photorechargeable Zinc‐Ion Batteries

AbstractThe solar‐driven photorechargeable zinc‐ion batteries have emerged as a promising power solution for smart electronic devices and equipment. However, the subpar cyclic stability of the Zn anode remains a significant impediment to their practical application. Herein, poly(diethynylbenzene‐1,3,5‐triimine‐2,4,6‐trione) (PDPTT) was designed as a functional polymer coating of Zn. Theoretical calculations demonstrate that the PDPTT coating not only significantly homogenizes the electric field distribution on the Zn surface, but also promotes the ion‐accessible surface of Zn. With multiple N and C=O groups exhibiting strong adsorption energies, this polymer coating reduces the nucleation overpotential of Zn, alters the diffusion pathway of Zn2+ at the anode interface, and decreases the corrosion current and hydrogen evolution current. Leveraging these advantages, Zn‐PDPTT//Zn‐PDPTT exhibits an exceptionally long cycling time (≥4300 h, 1 mA cm−2). Zn‐PDPTT//AC zinc‐ion hybrid capacitors can withstand 50,000 cycles at 5 A/g. Zn‐PDPTT//NVO zinc‐ion battery exhibits a faster charge storage rate, higher capacity, and excellent cycling stability. Coupling Zn‐PDPTT//NVO with high‐performance perovskite solar cells results in a 13.12 % overall conversion efficiency for the photorechargeable zinc‐ion battery, showcasing significant value in advancing the efficiency and upgrading conversion of renewable energy utilization.

Electrolyte effects on the alkaline hydrogen evolution reaction: A mean-field approach

This paper introduces the combination of an advanced double-layer model with electrochemical kinetics to explain electrolyte effects on the alkaline hydrogen evolution reaction. It is known from experimental studies that the alkaline hydrogen evolution current shows a strong dependence on the concentration and identity of cations in the electrolyte, but is independent of pH. To explain these effects, we formulate the faradaic current in terms of the electric potential in the double layer, which is calculated using a mean-field model that takes into account the cation and anion sizes as well as the electric dipole moment of water molecules. We propose that the Volmer step consists of two activated processes: a water reduction sub-step, and a sub-step in which OH− is transferred away from the reaction plane through the double layer. Either of these sub-steps may limit the rate. The proposed models for these sub-steps qualitatively explain experimental observations, including cation effects, pH-independence, and the trend reversal between gold and platinum electrodes. We also assess the quantitative accuracy of the water-reduction-limited current model; we suggest that the predicted functional relationship is valid as long as the hydrogen bonding structure of water near the electrode is sufficiently maintained.

Electroreductive Desorption of Alkanethiols on Gold and UPD Copper/Gold Surfaces Using In Situ Second Harmonic Generation

The reductive desorption of three alkanethiols: 1-decanethiol (DT), 1-dodecanethiol (DDT), and 1-octadecanethiol (ODT) was studied. Real-time second harmonic generation (SHG) was used to monitor changes at the surface as the self-assembled monolayer was electrodesorbed from a gold and UPD Cu/Au electrode through cyclic voltammetry (CV). Before and after reductive desorption, samples are examined ex situ with sum frequency generation (SFG) spectroscopy, X-ray photoelectron spectroscopy (XPS), and contact angle (CA). These techniques confirmed the electrodesorption of short-chain alkanethiols, while long-chain alkanethiols were proven to remain near the surface of the electrode. However, a difference was observed for a DDT monolayer on the UPD Cu/Au electrode. While DDT was easily desorbed from a gold substrate, DDT on the UPD Cu/Au electrode behaved similarly to a long-chain alkanethiol on gold. Significantly, SHG was able to determine the relative alkanethiol coverage even while the desorption-features in the CV were obscured by the hydrogen evolution current.

Ultrasound-assisted pulse electrodeposition of cobalt films

Pulse electrodeposition of cobalt was conducted in a sodium saccharin contained sulfate bath under silent or insonated conditions. The effects of pulse duty cycle, pulse frequency and ultrasonic agitation on the crystallographic structure and surface morphology of cobalt deposits were studied. All deposits obtained have a hexagonal close-packed structure, with its basal plane preferentially aligned parallel to the substrate surface. With the increase in duty cycle, texture coefficient for (100) plane increased whether ultrasonic agitation was imposed or not, while the imposition of ultrasonic agitation clearly decreased the texture coefficient for (100) plane. A finer-grained and smoother cobalt electrodeposit was obtained at 62.5 Hz and 25% duty cycle under insonated condition. To understand the roles that these operating parameters played in the electrodeposition, chronopotentiometry and linear sweep voltammetry were used to record the cathodic potential in cobalt deposition and hydrogen evolution current, respectively, which were associated with the morphological and structural change of cobalt deposits. Transmission electron microscopy was also employed to investigate the microstructure and crystal defect of cobalt films. A high density of stacking faults was detected in the cobalt films by high-resolution transmission electron microscopy.

Comprehensive study to design advanced metal-carbide@garaphene and metal-carbide@iron oxide nanoparticles with tunable structure by the laser ablation in liquid

Core-shell nanoparticles represent a class of materials that exhibit a variety of properties. By rationally tuning the cores and the shells in such nanoparticles (NPs), a range of materials with tailorable properties can be produced which are of interest for a wide variety of applications. Herein, experimental and theoretical approaches have been combined to show the structural transformation of NPs resulting to the formation of either NiFexCy encapsulated in ultra-thin graphene layer (NiFe@UTG) or Ni3C/FexCy@FeOx NPs with the universal one-step pulse laser ablation in liquid (PLAL) method. Analysis suggests that carbon in Ni3C is the source for the carbon shell formation, whereas the final carbon-shell thickness in the NPs originates from the difference between Ni3C and FexCy phases stability at room temperature. The ternary Ni-Fe-C phase diagram calculations reveal the competition between carbon solubility in the studied metals (Ni and Fe) and their tendency toward oxidation as the key properties to produce controlled core-shell NP materials. As an application example, the electrocatalytic hydrogen evolution current on the different NPs is measured. The electrochemical analysis of the NPs reveals that NiFe@UTG has the best performance amongst the NPs in this study in both alkaline and acidic media.

Dynamic Nanostructuring as a Tool to Fabricate High Performance Copper Based Hydrogen Evolution Electrocatalyst

Electrochemical production of hydrogen using electricity obtained from renewable sources such as Solar and wind represents an attractive avenue for clean and sustainable energy production and storage. Herein we report a low cost, highly active and stable copper based catalyst for hydrogen evolution reaction (HER) fabricated by chemical solution deposition. The catalyst exhibits self-optimizing behavior under hydrogen evolution conditions. Structural and morphological studies performed on pristine and self-optimized catalyst indicates that it undergoes nanostructuring from porous nanoplates to foam-like interconnected nanowires composed of ultra-small Cuo nanoparticles (2~3 nm in size) as shown in figure 1. Electrochemical impedance spectroscopy performed after various CV cycles suggests that there is substantial reduction in charge transfer resistance which is associated with large increase in effective double layer capacitance of the catalyst. This agrees well with the morphological analysis, wherein, nanostructuring was observed after CV cycling. A dissolution-reprecipitation based mechanism is suggested to explain the observed morphological changes. The proposed catalyst exhibits hydrogen evolution current of 10 mA/cm2 at an overpotential of 105 mV. The detailed results will be presented in the meeting. Figure 1. a) TEM image of Cu based catalyst after cycling, b) Linear sweep voltammograms of various electrodes obtained at a sweep rate of 10 mV/S Figure 1

Interconnected Nickel Nanowires – the Missing Link between Metallic High Surface Area Catalysts and High Porosity Foams

Porous and electrically conductive materials having extended surface area are attractive for wide range of applications, such as catalysis, sensing or energy storage. High surface area of the material provides higher reaction rates and lower electrode resistance. For instance, metallic sponges such as Raney nickel, having surface areas up to 100 m2/g show high catalytic activity during water electrolysis or heterogenous organic synthesis. However, low porosity and small average pore diameter limit their application for devices utilizing additional functional layers (e.g. active electrode materials in batteries). On the other hand, highly porous nickel foams are commonly used as current collectors for Ni- and Zn-based batteries, where sufficient loading of active material can be realized inside of the porous network. However, the surface area of such foams is more than three orders of magnitude smaller than that of the metallic sponges, lowering the potential for e.g. high rate operations of their parent devices. In this talk we will present a recently developed material composed of interconnected nickel nanowires of controllable diameter and distance. The nanowires assembly offers a unique combination of high surface area of metallic sponges and high porosity of metallic foams. The material is conveniently obtained by cheap and up-scalable electrochemical techniques. The unique nanostructural properties of the interconnected nanowires allow for high flexibility of the material and applications in e.g. flexible electronics or wearable sensors. As a proof-of-concept, we will present the performance of our structure for hydrogen generation during water electrolysis. Compared to nickel foams, the high surface area interconnected nanowires offers significantly higher hydrogen evolution currents, showing their potential for next generation electrolyzers and energy devices. Figure 1

Electrochemical behavior of the carbon black Vulcan XC-72R: Influence of the surface chemistry

The effect of chemical surface oxidation of the carbon black Vulcan XC-72R on the capacitance, tolerance to corrosion and electrochemical activity toward the hydrogen evolution reaction (HER) has been studied in 0.1 M NaHCO3. Acid treatments with HNO3 or a HNO3H2SO4 mixture resulted in a progressive introduction of oxygen-containing groups which led to a strong increase of the capacitance and a higher tendency to carbon corrosion. In contrast, an inhibition of the hydrogen evolution current (at potentials more negative than −1.0 V) was observed for oxidized samples in comparison to the un-treated material. HER was also tested in the presence of dissolved CO2 to study the influence of the surface chemistry on the CO2 electroreduction. An inhibition of the H2 evolution current was evidenced in the CO2 saturated electrolyte due to the adsorption of species from CO2 reduction. A strong hydrogen current decrease (65–78%), and thus a higher tendency to adsorb (CO2)red species, was obtained on the original Vulcan and the HNO3-treated samples, in comparison to the carbon oxidized with HNO3H2SO4 (15%), which could be related to the highest content of basic groups of the last carbon.

Ammonium Ions Intercalated 1T-MoS2 for Enhanced Electrochemical Hydrogen Production

Molybdenum disulphide (MoS2), a 2D layered transition metal dichalcogenide (TMDC) is being studied as an effective catalyst for Hydrogen Evolution Reaction (HER) in electrochemical water splitting. Optoelectronic properties of nanostructured MoS2 make them a potential materials for energy conversion and energy storage.[1-2] MoS2 exhibits 2 major stacking polytypes, 2H and 1T based on their coordination symmetry, where 2H is trigonal prismatic (D3h), 1T exists in octahedral coordination (Oh). 2H phase is a semiconductor where sulfur edges are only active, but 1T phase is metallic with both edge and basal planes active for HER. However, 1T is metastable in nature and easily converted into 2H [3]. To enhance the HER rate, alkali metals (Na, K, Li) are intercalated into 1T MoS2. The intercalation of alkali metals (Li, Na, Mg) can increase the d-spacing and electronic conductivity between interlayer and reduce the barrier to the diffusion of large-sized ions.[4] Here we have reported a facile one-pot hydrothermal synthesis of 1T-MoS2 at various temperatures (120-200oC) to perform as effective catalysts for HER. The d-spacing of inter-layer expanded 1T-MoS2at various temperatures are 0.92nm. 1T MoS2 was prepared by hydrothermal method at various temperatures (120-200oC) using ammonium molybdate tetrahydrate and thiourea in aqueous solution as precursors. The calculated molar ratio of Mo:S in the solution was 1:4. Ammonium ions released from thiourea and ammonium molybdate intercalated into the layers of MoS2 which eventually increases the d-spacing. The crystallinity and phases of the MoS2 sample were analyzed using X–ray diffraction. In contrast to bulk 2H phase, the ammonium ion intercalated 1T phase shows two new peaks at 9.5o (002) and 18.95o (004) with a d-spacing of ~9.27Å and 4.67Å, respectively. The ammonium ion intercalation increases the d-spacing and thereby shifts in the (002) plane from 14.3o to 9.5o is observed. The change in the d spacing is 3.3 Å and matches with the size of hydrogen bonding diameter in ammonium ions (∼ 3.5 Å).[5] The crystallinity of the MoS2sample increased with increasing temperature. The sulfur composition is being further examined using X-ray photoelectron spectroscopy. The onset potential for HER decreases with increase in the crystallinity. The hydrogen evolution current also shows significant increase with increase in crystallinity. The enhanced interlayer spacing increases the diffusion of larger Hydronium ions into the layer which directly enhances the hydrogen evolution rate. Hydrogen evolution reaction mechanism is being studied using electrochemical studies such as Tafel polarization.

Enhanced Performance of Lead Acid Batteries with Bi2O2CO3/Activated Carbon Additives to Negative Plates

Bi2O2CO3/Activated carbon (AC) composite is successfully synthesized via a facile hydrothermal method and investigated as an additive for lead-acid batteries for the first time. Remarkable inhibition of hydrogen evolution reaction (HER) is demonstrated on the optimized content of 4 wt% Bi2O2CO3/AC additive, which suppresses the hydrogen evolution current by 93.1% and increases the overpotential of HER by 230 mV. In addition, 2 V 7 Ah lead-acid module cell with 4 wt% Bi2O2CO3/AC additive maintains a lifespan up to 19637 cycles, confirming the feasibility to construct high performance lead-acid battery.

Complexes of DNA with peptide derivatives of cisPt. Electroanalytical examination

The aquation of the core of two novel cisPt complexes led to the formation of diaquated and monoaquated forms for two examined Pt complexes with peptides. DNA extent of DNA platination by novel cisPt derivatives was estimated. This extent was dependent on base-sequence in DNA and type of cisPt complex. The electroreduction of the novel Pt complexes and their adducts with DNA at a GC electrode led to the formation of Pt nanoparticles. In consequence catalytic hydrogen evolution (HER) currents appeared; they were characterized in function of DNA platination extent and size, distribution and mass of electrodeposited Pt NPs. Linear relations were obtained for catalytic HER current and mass of electrodeposited Pt NPs vs. extent of DNA platination for novel peptide cisPt compounds. They have electroanalytical significance.

Empirical Insights into the CO2 Reduction Reaction Mechanism: A Study of the Reduction of CO2, CO and Formaldehyde on Cu Electrodes By Differential Electrochemical Mass Spectrometry

This work describes results from a first-ever attempt to employ differential electrochemical mass spectrometry (DEMS) of selectively pre-adsorbed reactants and (postulated) intermediates as a supplementary experimental approach in the study of electrocatalytic reaction mechanisms. For the specific case of the Cu-catalyzed electrochemical reduction of CO2, dilute solutions of CO2, CO and HCHO in aqueous KHCO3 were placed separately in a DEMS stationary thin-layer electrochemical cell in contact with a Cu electrode. Simultaneous faradaic-current (CV) and mass-spectrometric-current (MSCV) voltammograms were then obtained for each solution. The only reduction products detected by mass spectrometry were H2, CH4, H2C=CH2 and CH3CH2OH; CO was also assayed but only from the reduction of CO2. The results prompt the following empirical inferences: (i) The slight but not imperceptible drop in the hydrogen-evolution current may not be caused by CO poisoning. It also exists for HCHO, a more feeble adsorbate, in the absence of the monoxide. In addition, the adsorption strength of H2 is four times greater than that of CO. (ii) CO is the first product of CO2 reduction, as well as the first intermediate in more advanced reactions that include formation of pure and oxygenated hydrocarbons; this is in conformity with the (almost) unanimously held view. (iii) HCHO is not a precursor for C=C double-bond formation. (iv) HCHO is a secondary intermediate for the production of methane and ethanol. (v) The generation of CH4 and CH3CH2OH from adsorbed CO occurs via two pathways: one requires a theoretically postulated surface species, CO protonated on the C atom, and the other involves adsorbed HCHO, constituted after the rate-limiting protonation step. (vi) The generation of CH4 and CH3CH2OH from CO has a much higher activation barrier than conversions from HCHO; not unexpected since the reactions transpire after the slow Cu–OCH+ formation and, consequently, are not highly activated.

Corrosion of ruthenium dioxide based cathodes in alkaline medium caused by reverse currents

A reverse current obtained during power shutdowns in industrial processes, such as chlor-alkali production or alkaline water electrolysis, is deleterious for hydrogen evolving ruthenium dioxide (RuO2) based cathodes. It has been observed that RuO2 coatings after a power shutdown, necessary for e.g. maintenance, are severely damaged unless polarization rectifiers are employed. In this work we show why these types of cathodes are sensitive to reverse currents, i.e. anodic currents, after hydrogen evolution. RuO2 coatings deposited on nickel substrates were subjected to different electrochemical treatments such as hydrogen evolution, oxygen evolution, or reverse currents in 8M NaOH at 90°C. Polarity inversion was introduced after hydrogen evolution to simulate the effect of reverse currents. Because of chemical interaction with hydrogen, a significant amount of the RuO2 coating was transformed into hydroxylated species during cathodic polarization. Our study shows that these hydroxylated phases are highly sensitive to electrochemical corrosion during anodic polarization after extended hydrogen evolution.

Mechano-Electrochemistry and Fuel-Forming Mechano-Electrocatalysis on Spring Electrodes

Each material, in principle, possesses a continuum of electrochemical and electrocatalytic properties that can be reversibly tuned by mechanical stress over its elastic range. As an initial test of this hypothesis we investigate stainless steel extension springs as electrodes. Stretching the springs reversibly doubles the heterogeneous rate constant for electron transfer to a redox species in solution, Ru(NH3)6Cl3, while the charge transfer rate through a surface film of Ni(II/III) oxy-hydroxide increases ∼4-fold. Straining the springs near their elastic limit in 1 M NaOH increases the electrcatalytic hydrogen evolution current by ∼50% and the oxygen evolution current by ∼300%. Thus, even the small elastic strain (∼0.1% lattice deformation) that can be applied by stretching a spring leads to significant and reversible increases in the rates of: 1) electron transfer to a redox couple in solution, 2) charge transport through a surface film, and 3) electrocatalysis.

Electrodeposition of FeCoRu Alloy

The electrodeposition of FeCoRu alloys was studied with rotating disk electrode, surface pH measurements and galvanotstatic plating in a paddle cell. The Ru deposition does not occur until a potential of -0.9 V versus MSE is reached, much higher than the literature reversible potential. In the FeCoRu system, the presence of Ru inhibits the Fe plating rate but exerts no effect on the Co. Surface pH measurements further confirmed the high potential for Ru deposition and a significant hydrogen evolution reaction was observed causing enhanced local agitation at the electrode surface. The effect of complexing agent was also studied for FeCoRu plating. The presence of citrate, tartrate or histidine, were all found to decrease the current efficiency at the conditions of study. While the decrease observed in the citrate and tartrate cases was probably due to the buffering effect, which increases the hydrogen evolution current, histidine was believed to complex with metal cations and to inhibit the metal deposition.

Influence of boric acid and Mn on electrolytic deposition of Co from low concentration sulphamate electrolytes

The electrolytic deposition of Co from low concentration sulphamate electrolytes, containing manganese and boric acid, has been investigated. Growth of multilayered dendrite formations, comprising successive layers with very high Co or O content, is observed at high deposition potentials. For cobalt deposits, the obtained systems contain enormous amounts of incorporated hydrogen, ∼4200 ppm. The dependence of the hydrogen content remaining after thermal treatments at different temperatures suggests the presence of two types of bonded hydrogen. Cyclic voltammetry (CVA) has been used to study the electrode processes by sweeping the potential to different values. Some unexpected effects are established in the cathodic part of the CVA curves, related to an abrupt decrease in hydrogen evolution current and its subsequent oscillations at this lower value. The apparent contradiction between the huge amounts of incorporated hydrogen and the low cathodic currents of hydrogen evolution is explained by the reduced share of recombinant hydrogen at the expense of its absorption in the bulk of the deposit.

Hydrogen adsorption and hydrogen evolution reaction on a polycrystalline Pt electrode studied by surface-enhanced infrared absorption spectroscopy

Hydrogen evolution reaction (HER) on a polycrystalline Pt electrode has been investigated in Ar-purged acids by surface-enhanced infrared absorption spectroscopy and electrochemical kinetic analysis (Tafel plot). A vibrational mode characteristic to H atom adsorbed at atop sites (terminal H) was observed at 2080–2095 cm −1. This band appears at 0.1 V (RHE) and grows at more negative potentials in parallel to the increase in hydrogen evolution current. Good signal-to-noise ratio of the spectra enabled us to establish the quantitative relation between the band intensity (equivalently, coverage) of terminal H and the kinetics of HER, from which we conclude that terminal H atom is the reaction intermediate in HER and the recombination of two terminal H atoms is the rate-determining step. The quantitative analysis of the infrared data also revealed that the adsorption of terminal H follows the Frumkin isotherm with repulsive interaction.

Mechanisms of Oscillations and Formation of Nano-Scale Layered Structures in Induced Co-Deposition of Some Iron-Group Alloys (Ni−P, Ni−W, and Co−W), Studied by an In Situ Electrochemical Quartz Crystal Microbalance Technique

We have investigated mechanisms of oscillations and formation of nano-scale layered structures in induced co-deposition of some iron-group alloys (Ni-P, Ni-W, and Co-W) that have unique properties and are widely used in industries. Detailed in situ electrochemical quartz crystal microbalance (EQCM) experiments have revealed that the electrodeposition (induced co-deposition) of the alloys has negative differential resistances (NDRs), from which the oscillations and the layer-structure formation arise. The NDRs, however, cannot necessarily be seen in current-potential curves owing to overlap of hydrogen evolution current, indicating that the oscillations are of a hidden-NDR (H-NDR) type. The EQCM experiments have also shown that electrolyte components (such as H2PO2- and WO4(2-)) or related species are adsorbed at the electrode (deposit) surface and act as a promoter for the co-deposition reaction and that the NDRs arise from desorption of the adsorbed promoter. Interestingly, the adsorbed promoter is drawn into the deposition reaction itself, thus resulting in the alloy deposits. This mechanism was supported by in situ EQCM investigations of the oscillation as well as Auger electron spectroscopic (AES) analyses of deposits formed during the oscillation. The present work has for the first time clarified a general mechanism for the induced co-deposition reactions of some industrially important iron-group alloys (Ni-P, Ni-W, and Co-W).

Improvements to active material for VRLA batteries

In the past several years, there have been many developments in the materials for lead–acid batteries. Silver in grid alloys for high temperature climates in SLI batteries has increased the silver content of the recycled lead stream. Concern about silver and other contaminants in lead for the active material for VRLA batteries led to the initiation of a study by ALABC at CSIRO. The study evaluated the effects of many different impurities on the hydrogen and oxygen evolution currents in float service for flooded and VRLA batteries at different temperatures and potentials. The study results increased the understanding about the effects of various impurities in lead for use in active material, as well as possible performance and life improvements in VRLA batteries. Some elements thought to be detrimental have been found to be beneficial. Studies have now uncovered the effects of the beneficial elements as well as additives to both the positive and negative active material in increasing battery capacity, extending life and improving recharge. Glass separator materials have also been re-examined in light of the impurities study. Old glass compositions may be revived to give improved battery performance via compositional changes to the glass chemistry. This paper reviews these new developments and outline suggestions for improved battery performance based on unique impurities and additives.