Tafel Slope Research Articles

Engineering Hybrid Transition Metal Dichalcogenide as Highly Active Electrode for Water Electrolysis

AbstractWater electrolysis plays a vital role in green energy systems and there is an absolute need for abundant, affordable, and effective catalysts for both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER). Despite existing challenges, the exploration of transition metal‐based electrocatalysts with superior performance in alkaline water splitting is critical for advancing the hydrogen economy. This study focuses on the electrocatalytic potentials of FeS2, CoSe2, and FeS2@CoSe2 hybrid nanocomposites in response to the increasing demand for sustainable energy production. The prepared materials were synthesized hydrothermally and characterized using X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), energy‐dispersive X‐ray spectroscopy (EDX), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) to examine their structural properties, elemental composition, and morphological features. Notably, the F@C−B nanocomposite exhibited outstanding HER performance, requiring only 97 mV of overpotential to achieve a current density of 10 mA cm−2. Similarly, the F@C−C nanocomposite demonstrated impressive OER efficiency with an overpotential of merely 302 mV at the same current density. The involvement of the Volmer–Heyrovsky mechanism was confirmed through Tafel slope analysis, revealing the improved surface‐active sites and reduced charge transfer resistance of the nanocomposite. The FeS2@CoSe2 nanocomposite with synergistic effects, displayed exceptional electrocatalytic properties, positioning it as a promising candidate for overall water splitting. This work introduces a novel approach to developing highly efficient and cost‐effective electrocatalysts, offering a viable alternative to precious metal‐based counterparts.

Advanced characterization of alkaline water electrolysis through electrochemical impedance spectroscopy and polarization curves

Improved electrolyzer components are needed to make alkaline water electrolyzers more flexible and durable. The performance of these new components can be assessed through in situ electrochemical characterization in the form of polarization curves and electrochemical impedance spectroscopy (EIS). Presently, EIS is still mostly used for the IR-correction of the polarization curve, but more valuable information can be extracted. In this work we show how EIS data can be used to determine the dependence of ohmic resistance on current density, to derive anodic and cathodic Tafel slopes and exchange current densities from fitted charge transfer resistances and to derive anodic and cathodic capacitances from fitted constant phase elements. We do this for both a two electrode alkaline electrolysis flow cell setup as well as for a three electrode beaker type setup with 2D nickel electrodes. The presented tools can be used in performance studies of new and existing electrodes and membranes in alkaline water electrolysis.

304L Austenitic Stainless Steel Corrosion Studies in Neutral Environment in Presence of Sulfite Ions

Abstract This paper examined the influence of the sulfite concentration introduced in the electrolyte added to the neutral solution (1 mol L-1 Na2SO4) on the corrosion process of 304L stainless steel material. 304L. The accelerated effect of sulfite ions under corrosion rate of 304L austenitic stainless steel was demonstrated using electrochemical techniques such as linear sweep voltammetry at a low scan rate −1 mV s−1, the Tafel slope method, chronoamperometry, and electrochemical impedance spectroscopy. Electrochemical studies were conducted using a BioLogic SP150 potentiostat/galvanostat. Stainless steels are the most varied and intricate group among all steels. Among them, 304L austenitic stainless steel is one of the most commonly utilized alloys, prized for its excellent corrosion resistance and strength, hygienic and aesthetic properties, affordability, good formability, and effective weldability. [1-3]. In modern industry, the amount of austenitic stainless steel represents only about 2% of the total steel production manufactured globally. This type of steel is commonly employed in chemical engineering, metal extraction, desalination and wastewater treatment plants, the oil and gas sector, transportation and aerospace industries, the food and beverage sector, as well as in architecture and construction engineering. [1].

Corrosion of Copper, Cupronickel, Nickel Aluminium Bronze and Super-Duplex Stainless Steel Rotating Cylinder Electrodes in Seawater under Turbulent Flow Conditions

The corrosion of uncoated metals in a marine environment restricts the choice of suitable engineering metals and alloys. Anodic dissolution of metal and cathodic reduction of oxygen are important processes and formation of a surface oxide film can affect both electrode reactions. Charge transfer and mass transfer data can provide information on corrosion rate and mechanism. Several metals and alloys having a history of use in marine engineering are considered, including copper, two copper alloys (cupronickel and nickel aluminium bronze) plus a more recent addition to strong, corrosion resistant alloys (a super duplex stainless steel). The rotating cylinder electrode offers the benefits of a controlled, turbulent flow of electrolyte, facilitating controlled mass transfer in a compact cell geometry which is well-suited to bench-top operation. These features are illustrated using a variety of electrochemical techniques, including open-circuit potential vs time monitoring, linear sweep voltammetry, rotation speed step- or potential step current transients and linear polarisation resistance measurements. Seawater taken from Langstone Harbour, Hampshire, UK, was filtered, air-saturated, pH 8.0 and maintained at 25 °C. Dimensionless group correlations and graphical plots (using an analogous approach to the Koutecky-Levich equation for an RDE) enabled contributions of charge transfer-, mixed- and mass transfer- controlled data to be appreciated, allowing the Tafel slopes of electrode reactions, the diffusion coefficient of dissolved oxygen, the mass transfer coefficient for oxygen reduction and the mean corrosion rate to be estimated.

Development of a free-standing flexible electrode for efficient overall water-splitting performance via electroless deposition of iron-nickel-cobalt on polyacrylonitrile-based carbon cloth

Developing cost-effective and highly efficient electrodes for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is crucial, particularly for alkaline OER and HER. Herein, electroless plating of iron-nickel–cobalt (Fe–Ni–Co) electrocatalyst on a flexible polyacrylonitrile (PAN)-based carbon cloth (CC) was performed to synthesize a free-standing catalytic electrode for bifunctional electrocatalysts. The three-dimensional porous backbone of PAN-based CC and the synergistic effect between Fe-Ni-Co and corresponding hydroxides result in outstanding OER and HER activities, that is low overpotentials of 230 and 150 mV at 10 mA cm−2 and Tafel slopes of 63 and 57.1 mV dec–1, respectively. Additionally, a complete alkaline electrolyzer was constructed using Fe-Ni-Co plated PAN-based CC as both the cathode and anode. When operated at 10 mA cm−2, this setup enabled efficient water splitting at a low potential of 1.57 V. This study provides new opportunities for the development of advanced Fe-Ni-Co electrocatalyst with superior bifunctional OER and HER performance and cost-effectiveness that are suitable for integration into PAN-based CC via electroless plating.

Electrocatalysis of Co/CoxOy nanofilms supported by synchronously nitrogen-doped Ketjenblack carbon towards oxygen reduction reaction

Developing a highly active and stable non-precious metal catalyst for oxygen reduction reaction (ORR) is of great practical significance for advancing fuel cell technology. In this work, a continuous two-step hydrothermal reaction followed by high temperature pyrolysis were employed to achieve in situ N-doping preferentially into Ketjenblack carbon (KB-N) and composite of KB-N and Co/CoxOy nanofilms (Co/CoxOy-NFs) as Co/CoxOy-NFs@KB-N. The N-doped state strongly affects the ORR activity of catalyst. All prepared Co/CoxOy-NFs@KB-N catalysts exhibit observably improved ORR activity compared with the basal KB-N and N-doped Co/CoxOy-NFs, in which the optimal Co/CoxOy-NFs@KB-N catalyst demonstrate the positive Eonset (0.864 V) and E1/2 (0.788 V) vs. RHE, the low Tafel slope (69.27 mV dec−1), implying quick ORR kinetics. And, the Co/CoxOy-NFs@KB-N catalyst exhibits highly electrochemical durability. The KB-N substrate can purify Co valence in CoO component, promote amorphization of CoO crystalline structure and enhance the interaction between Co/CoxOy-NFs and KB-N in Co/CoxOy-NFs@KB-N catalyst. Thus electronic effect, structural effect and synergistic effect can strengthen O2 adsorption, provide enough adsorbed sites and accelerate electron transfer, resulting in prominent ORR performance of Co/CoxOy-NFs@KB-N catalyst.

Designing Mo-based transition metal dichalcogenides for sustainable hydrogen production: Anionic substitution and DFT insight

Anionic substitution is an effective approach to optimize the catalytic activity of Mo based transition metal dichalcogenide (TMD)- MoS2 towards hydrogen evolution reaction (HER). By optimizing the S-to-Se ratio, materials with the ideal Gibbs free energy of hydrogen adsorption (ΔGH) values are synthesized (MoS2, MoS1.4Se0.6, MoS1.2Se0.8, MoSSe, MoSe2) and their HER performance is examined in 0.5 M H2SO4 solution. Density functional theory calculations of hydrogen adsorption energy on the surface of the electrocatalysts show that Se substitution facilitates electron transfer between the catalyst surface and the hydrogen donor, thereby lowering the additional potential required for water splitting, making MoS1.2Se0.8 the most favorable HER electrocatalyst with the lowest value of adsorption energy. Further enhancement in the electrocatalytic activity of mixed anion TMDs has been achieved by the incorporation of carbon nanotubes (CNTs). MoS1.2Se0.8-CNT nanocomposite exhibits superior HER performance with an overpotential of 118 mV and a Tafel slope of 63 mV/decade as compared to MoS1.2Se0.8 sample owing to the synergetic effect from CNTs and MoS1.2Se0.8.

Microwave fostered sustainable synthesis of Nb2O5 – ZnO nanomaterial for efficiency amplification in high performing energy systems

This study presents the first report on the microwave approach combined with improved sustainable synthesis of zinc oxide (ZnO) and niobium oxide (Nb2O5) to generate Nb2O5 – ZnO nanospheres. Following the development of nanospheres, the band gap energy decreased to 3.25 eV, and the average crystallite size was found to be 62.49 nm. The nanospheres had a mixed crystalline phase of hexagonal and orthogonal crystals. This material has demonstrated a predisposition towards hydrogen production in the electro-catalytic tests, with a minimal overpotential (ηHER) and a Tafel slope values of 127 mV and 125.6 mV dec-1. Furthermore, nanospheres decorated electrode remained intact in electrolyte environment for 1500 min and exhibited profound charge storage of 204.93 F g-1. 15% PV efficiency was attained by the air-processed perovskite solar cell thanks to the interface passivation functionality. The commendable performance of the binary Nb2O5 – ZnO nanospheres have validated their prospects for practical applications.

High entropy metal oxide/TiO2 nanocomposite for electrocatalytic overall water splitting

Here, high entropy metal oxide (HEMO) containing five elements (In, Co, Ni, Fe, and Zn) was loaded onto titanium dioxide (TiO2) and explored its electrochemical properties for overall water-splitting in alkaline media (1 M KOH). Here, we confirmed that HEMO-TiO2 nanocomposite boosts oxygen evolution reaction (OER) via lattice oxygen participation. Electrochemical investigations revealed that the HEMO-loaded TiO2 showed remarkable electrocatalytic properties for OER. The electrocatalyst demonstrated high performance for OER with low overpotential (336 mV @ 10 mA cm−2), small Tafel slope (56 mV dec−1), and high stability over 20 h. Moderate hydrogen evolution reaction (HER) performance was achieved for the HEMO-TiO2 nanocomposite regarding overpotential (191 mV @ 10 mA cm−2) and Tafel slope (121 mV dec−1) with high stability over 20 h. The HEMO-TiO2 based water-splitting device exhibited a low voltage (1.71 V) to reach 10 mA cm−2. Notably, the modified interface at an electrode/electrolyte effectively alters the active sites and boosts the electronic transfer, leading to enhanced splitting efficiency. This study opens a new route for realistically creating heterogeneous interfaces to increase their electrochemical performances, which may help to speed up the progress of nonprecious catalysts for water splitting.

Doping-mediated interface engineered Ni3S2: Economically viable electrochemical methanol-mediated water splitting

Electrochemical water splitting is the front runner to meet the global green hydrogen demand. The development of a noble metal-free earth-abundant electrocatalyst is desired to rationalize an economically viable electrochemical water-splitting system. The sluggish anodic oxygen evolution reaction (OER) is the bottleneck of the electrochemical water-splitting system. Herein, to improve OER kinetics, group VIB elements such as chromium (Cr), molybdenum (Mo), and tungsten (W) doped nickel sulfides (Ni3S2) nanosheets (NSs) are synthesized by two-step hydrothermal method to modulate the intrinsic electrocatalytic activity of the pure Ni3S2. Among all the doped samples, the Cr-doped Ni3S2 catalyst exhibited excellent OER with an ultra-low overpotential of 248 mV and MOR with a potential of 1.36 V @ 10 mA cm−2 vs RHE achieving a lower Tafel slope of 95.5 mV/dec and 46.4 mV/dec and outstanding durability with negligible degradation respectively. Furthermore, the Pt/C||Cr-Ni3S2 (1.48 V) system outperforms commercial Pt/C||RuO2 (1.53 V @ 10 mA cm−2) in a two-electrode configuration. The methanol-mediated hybrid water splitting system only warranted a cell voltage of 1.38 V to attain 10 mA cm−2 for the Pt/C||Cr-Ni3S2 system in the presence of 0.1 M methanol (MeOH). The methanol oxidation reaction (MOR) mediated the hybrid water electrolyzer system demonstrates reduced operation cell voltage while additionally electro-synthesizing formate as a value-added chemical. The overall work is motivated to rationalize the importance of doping-mediated interface-engineered catalyst synthesis to improve the electrocatalytic efficiency of the hybrid water electrolyzer.

In Situ Construction of SnS2@SnO2 Heterostructure for Photo-Assisted Electrocatalysis of Oxygen Evolution Reaction.

Photo-assisted electrocatalysis has arisen as a promising approach for hydrogen generation by incorporating photocatalysts into electrocatalysts. 2D SnS2 is a photocatalyst that absorbs visible light. However, the rapid recombination of photo-generated electron-hole pairs significantly reduces the overall photocatalytic efficiency of SnS2, limiting its practical application. Thus, this study prepares an in situ heterojunction SnS2@SnO2 using a one-step hydrothermal method. The degradation efficiency of methyl orange (MO) using SnS2@SnO2 is measured, achieving a degradation rate of 92.75% within 1h, which is 1.9 times higher than that of pure SnS2. Additionally, FeNiS/SnS2@SnO2 is synthesized and exhibited significant improvements in the photo-assisted oxygen evolution reaction (OER). It achieves an overpotential of 260mV and a Tafel slope of 65.1mVdec-1 at 10mAcm-2, showing reductions of 11.8% and 31.8%, respectively, compared to FeNiS alone. These enhancements highlight the strong photo-response capability of SnS2@SnO2. Under the internal electric field of SnS2@SnO2, the photogenerated electrons in the conduction band of SnS2 quickly move toward SnO2, facilitating efficient photocatalytic reactions. FeNiS, with a lower Fermi energy level (EF), facilitates electron transfer from SnS2@SnO2 and enhances OER performance by efficiently participating in the reaction. This study paves a new path for 2D photocatalyst materials.

Design of NiPS3/MoS2/rGO hybrid electrocatalyst for electrochemical hydrogen evolution

The design and development of efficient electrocatalysts for hydrogen evolution reaction is presently a pressing task to overcome future energy demands. In the present study a hybrid layered compound NiPS3/MoS2/rGO (NMR) is investigated as an electrocatalyst for hydrogen evolution reaction (HER). The metal trichalcogenidophosphates (MTPs), transition metal dichalcogenides and reduced graphene oxide materials based electrocatalysts are promising material for HER. The hybrid layered compound NMR displays good electrocatalytic activity in acidic medium in comparison to its counterparts MoS2/rGO and NiPS3/rGO with an overpotential and Tafel slope of 152 mV vs RHE and 75 mV/dec, whereas MoS2/rGO and NiPS3/rGO shows an overpotential of 206 mV and 223 mV vs RHE with a Tafel slope value of 146 mV/dec and 154 mV/dec respectively. The hybrid electrocatalyst exhibited high stability up to 1000 cycles with a stable current. The high HER activity of NMR is attributed to synergistic effect of electrocatalysts where P and S of NiPS3 acts as an appropriate hydrogen adsorption sites and catalytically active Mo edge sites of MoS2 with high charge carrier property of rGO contributed to enhanced hydrogen evolution reaction.

Preparation of Ni nanocone/Grid electrodes by laser-electrodeposition combined process as an efficient and stable electrocatalyst for hydrogen evolution reaction

Hydrogen is a renewable and environmentally friendly energy carrier and is considered a viable alternative to fossil fuels. Consequently, developing electrodes with excellent hydrogen evolution electrocatalysis is a top priority in research. However, the use of flat electrodes as cathode substrates by most researchers limits the electrocatalytic active area of the prepared electrode. To address this issue, it is essential to prepare a micro-nano structure on a cathode substrate before electrodeposition. This study introduced a novel Ni nanocone/Grid electrode, obtained through a combined laser-electrodeposition process to investigate its electrocatalytic activity and stability for the hydrogen evolution reaction (HER). Various techniques, including linear sweep voltammetry (LSV), electrochemical impedance spectra (EIS), cyclic voltammetry (CV), and chronopotentiometry (CP) in 1 M KOH solution, were employed to assess the HER electrocatalytic performance of the Ni nanocone/Grid electrodes. The experimental results demonstrated that the electrodes could achieve current densities of -10, -20, and -100 mA/cm2 with corresponding overpotentials of -281, -308, and -390 mV, respectively. Additionally, the Tafel slope of these electrodes was found to be only -82.05 mV/dec. The enhanced catalytic performance of the electrode was attributed to the synergistic effect of the grid-like and nanocone structures, which significantly increased the electrocatalytically active area and improved surface hydrophilicity, thereby boosting electrocatalytic performance. The simplicity of the preparation method and the exceptional performance of the electrode provide a promising new avenue for future research on HER electrocatalysts.

Uniform carbon pillars array grown on boron doped diamond for high-performance supercapacitors and hydrogen evolution reactions

Carbon materials have marvelous ability in energy storage and microelectronics as a result of the high specific surface area and electrical conductivity. However, the low stability and the low power density caused by low potential window make it particularly difficult for their application in aqueous electrolysis. In this study, boron doped diamond (BDD) with wide potential window is used as substrate and Ni as catalyst to grow uniform carbon pillars (CP) by microwave plasma chemical vapor deposition method. The composite structure (CP/BDD) yields significant specific capacity (91.64 mF cm−2 at 0.1 mA cm−2) and cycling stability (92.3 % retention rate after 20,000 cycles) when used as the electrode of supercapacitors, superior to most of BDD-based electrodes. The prepared symmetrical supercapacitor devices maintain their excellent electrochemical performance characteristics (power density of 4.4 mW cm−2 and energy density of 13.4 μW h cm−2), as well as high cycling stability. In addition, the electrode has considerable application potential in electrochemical hydrogen production with low hydrogen evolution potential and small Tafel slope value. These results illustrate the potential of BDD based composites for using as energy storage electrodes for electronic products and energy conversion equipment.

Reduced graphene oxide supported meso-pyridyl BODIPY-Cobaloxime complexes for electrocatalytic hydrogen evolution reaction

Creating innovative catalysts utilizing nonprecious metals for the electrocatalytic hydrogen evolution reaction (HER) poses a significant difficulty. We present a cobaloxime (Cox) complex having pyridine (2-Cox) and tetrafluorophenyl-thio-pyridine (4-Cox) functional groups, which contains a 4,4-Difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) moiety. This combination serves as a catalyst for proton reduction and is immobilized onto reduced graphene oxide (rGO) by π–π stacking between the cobaloxime complex and rGO. Moreover, the unique complex's structures were determined through the application of ultraviolet–visible spectroscopy (UV–Vis), Fourier Transform Infrared spectroscopy (FT-IR), X-ray diffraction spectroscopy (XRD), and scanning electron microscopy (SEM). The electrocatalytic activity of the two rGO/2-Cox and rGO/4-Cox electrodes towards hydrogen (H2) were examined under both alkaline and acidic conditions. The cobaloxime-modified rGO electrodes demonstrate superior electrocatalytic performance for the HER under acidic conditions compared to alkaline conditions. The overpotential at a current density of 10 mA cm−2 for rGO/2-Cox in 0.5 M H2SO4 is −0.342 V, which is notably lower than the overpotential of rGO/4-Cox (−0.496 V). The Tafel slope for the rGO/2-Cox electrode in a 0.5 M H2SO4 solution is 111 mV.dec−1, but for the rGO/4-Cox electrode it is 156 mVdec−1. This discrepancy suggests that the rGO/2-Cox electrode demonstrates better performance in the HER compared to the rGO/4-Cox electrode.

Spinel-type calcium manganese oxide adorned on g-CN composite: A highly proficient electrocatalyst for oxygen evolution reaction (OER)

A comprehensive study was performed on water electrolysis to address environmental challenges and energy issues. Eco-friendly and renewable energy systems are required to produce cost-effective electro-catalysts with long-term durability and higher electrocatalytic efficiency to enhance OER. Spinel oxide has recently been used as a promising substitute for transition metal catalysts. They can function as very effective electrocatalysts in water oxidation processes. In current study, the CaMn2O4/g-CN composite was prepared using the hydrothermal technique in 1.0 M KOH in primary media. Distinctive physical and electrochemical analyses evaluated the prepared material's morphology, structure and electrocatalytic components. The composite material showed enhanced electrocatalytic efficacy for OER having a reduced overpotential (η) of 220 mV than pure CaMn2O4 278 mV and possesses a minimal Tafel value (35 mV/dec) contrasted with pristine CaMn2O4 (57 mV/dec). In case of overpotential, the composite material revealed good performance than its pure material while the Tafel slope of CaMn2O4/g-CN exhibited lower value than its individual material (CaMn2O4). Additionally, cyclic stability and chronoamperometric studies measured the electrodes' durability over 30 h. Electrochemical impedance spectroscopy (EIS) investigations indicated that charge transformation at an electrode-electrolyte surface might be feasible with minimal Rct value (0.19 Ω) and it showed excellent improved performance (63 %) better than its pure material, leading it to boost OER properties, attributed to its remarkable electrical conductivity, greater surface area and outstanding stability. These outstanding electrochemical features of the CaMn2O4/g-CN differentiate as an attractive choice for future OER utilization.

Elucidating the increased ohmic resistances in zero-gap alkaline water electrolysis

This study investigates the increased ohmic resistances observed in zero-gap alkaline water electrolyzers, aiming to provide insights that can help enhance electrolyzer efficiency and enable operation at higher current densities. Electrochemical impedance spectroscopy (EIS) has been employed in combination with chronopotentiometry, utilizing a custom-designed flow cell with nickel perforated electrodes and a Zirfon UTP 500 diaphragm. Observed differences in area-ohmic resistance values obtained through I-V fitting and EIS, are ascribed to a non-linear Tafel slope at higher current densities. Ohmic resistance values measured with EIS are up to 27% higher than the ex-situ determined value, a significantly smaller percentage than expected based on previous studies. The presence of bubbles outside and inside the diaphragm is identified as the key factor contributing to this increased resistance. We recommend the use of an improved fitting approach, accounting for non-linear Tafel behavior, and the use of a 4-terminal configuration when performing EIS measurements to minimize cable and contact resistance.

Temperature dependent electrocatalytic activity of molybdenum-based ZIF-67 nanorods for water splitting

Several strategies have been adopted to enhance the electrochemical features of metal-organic framework structures for water splitting, however, a suitable conditions can effectively boost the electrocatalytic activity. Herein, molybdenum-based zeolite imidazolate frameworks (Mo2gZIF-67 and Mo4gZIF-67) have been synthesized by solvothermal process and electrocatalytic activity was examined at various elevating temperatures of 1 M KOH electrolyte. Mo4gZIF-67 nanorods showed the overpotential (η10) of 358 mV at 20 °C, which was improved to 221 mV at 80 °C for the oxygen evolution reaction. Mo4gZIF-67 nanorods exhibited the Tafel slope of 77 mV dec−1 at 80 °C and followed the Volmer-Heyrovsky mechanism. LSV curves reveal that Mo4gZIF-67 nanorods showed a greater current density and a good turnover frequency (TOF) of 221.0 ms−1 at the fixed VRHE of 0.7 V. Similarly, Mo4gZIF-67 nanorods revealed the η10 of 181 and 93 mV at 20 and 80 °C, respectively for the HER process. Mo4gZIF-67 nanorods displayed a Tafel slope of 95 mV dec−1 and TOF of 213.50 ms−1. The enhanced electrocatalytic activity may be due to rising temperatures, enhanced electrical conductivity at rising temperatures, well defined nanorods shape and greater ECSA, which provided the active sites and facile the flow of charge carriers for oxygen and hydrogen evolution reaction. The electrocatalyst, Mo4gZIF-67 nanorods exhibited a uniform current density during stability tests for 30 h at 20 °C, which was increased at 80 °C. Temperature elevation remarkably enhanced the HER and OER characteristics of the Mo4gZIF-67 nanorods and suggested an effective electrocatalyst for water splitting.

Oxygen Evolution Behavior of Ni-Containing Alloy Electrodes in NaOH–KOH Hydrate Melt

We investigated the oxygen evolution behavior of nine types of commercially available Ni-containing alloys in a NaOH–KOH hydrate melt. The oxygen overpotential of all Ni-containing alloys was lower than that of the Ni electrode (453 mV) at 500 mA cm–2 and 150°C. The Kovar (Fe–Ni–Co alloy) electrode exhibited the lowest oxygen overpotentials of 280 mV at 150°C and 227 mV at 200°C. The Tafel slope of the Kovar electrode at 150°C was 63 mV dec–1, which was slightly lower than that of the Ni electrode (67 mV dec–1). The upper limit of the Tafel region for the Kovar electrode was extended to a higher current density of 300 mA cm–2 compared to that for the Ni electrode (100 mA cm–2) at 150°C. It further extended to 1000 mA cm–2 at 200°C, indicating that highly efficient water electrolysis can be expected.

Harnessing dysprosium telluride/GPE as an effective electrode for energy storage and conversion

Hydrogen stands out as a clean alternative to fossil fuels, and its production via water electrolysis is promising, although the slow kinetics of the oxygen evolution reaction (OER) pose a significant challenge. Alongside energy conversion, the quest for effective energy storage remains critical. This study explores the potential of dysprosium telluride (Dy2Te3) as a highly efficient catalyst for OER and a supercapacitor electrode. The hydrothermally synthesized Dy2Te3 exhibits exceptional OER activity, characterized by an overpotential of 294 mV at 1.48 V vs. RHE, a low Tafel slope of 48 mV dec−1, and minimal interfacial resistance of 13 Ω. In a 1.0 M KOH solution, Dy2Te3 nanoparticles demonstrate outstanding supercapacitor performance, achieving a power density of 283.5 W kg−1, specific capacitance of 645.33 F g−1, and energy density of 22.8 Wh kg−1 at 1 A g−1. The high performance is attributed to enhanced electrical conductivity and a low impedance of 0.352 Ω in a three-electrode system. In a practical two-electrode configuration, Dy2Te3 nanoparticles deliver a specific capacitance of 479 F g−1, energy density of 94 Wh kg−1, and power density of 0.32 kW kg−1, with a reduced interfacial resistance of 1.03 Ω. These results underscore the potential of Dy2Te3 as a viable electrode material for both supercapacitors and water splitting, offering valuable insights into the application of lanthanide-based metal chalcogenides in energy technologies.