KOH Solution Research Articles

Microstructure, corrosion resistance and high temperature oxidation properties of AlCrFeNiCu high-entropy alloy coating by high-speed laser cladding

AlCrFeNiCu high-entropy alloy (HEA) coating was prepared on Zirconium (Zr) rod by high-speed laser cladding (HSLC) technique. The effect of different laser power and scanning speed on the forming quality of the coating was studied. When the specific energy density was in the range of 3.0–3.2 J/mm2, the AlCrFeNiCu HEA coating with good adhesion to the substrate, low dilution rate (small heat affected zone) and no cracks were obtained. The phase structure, microstructure, microhardness, corrosion resistance and high temperature oxidation resistance of the coating were tested and analyzed. The results show that the AlCrFeNiCu HEA coating is composed of 76.9 % BCC phase and 23.1 % FCC phase, in which the BCC phase is mainly composed of disordered BCC phase rich in Cr and Fe elements and ordered B2 phase rich in Al and Ni elements, and the FCC phase is rich in Cu elements. Due to the rapid cooling of HSLC, the coating structure gradually changes from columnar crystal to equiaxial crystal from bottom to top. The hardness of the coating is as high as 805 HV, which may be caused by the solution strengthening effect, lattice distortion effect and slow diffusion effect of HEA. In 3.5 % NaCl solution and 0.1 mol/L KOH solution, the self-corrosion current density of the coating is 4.209 × 10−8 A/cm2 and 4.331 × 10−8 A/cm2, respectively. The passivation film on the surface of the coating is composed of a variety of oxides, and the oxygen vacancy density of the passivation film in the two solutions is 2.552 × 1020 cm−3 and 5.794 × 1020 cm−3, with fewer pitting pits on the surface. The structural integrity of the coating can be maintained after 60 min oxidation at 1200 °C. The oxidation process follows the growth kinetics curve, and the surface oxides mainly comprise FeAl2O4, Al2O3 and Cr2O3. AlCrFeNiCu HEA coating improves the corrosion resistance and high temperature oxidation resistance of the Zr-4 alloy.

High performance oxygen reduction and evolution reactions by graphitization of nickel –cobalt framework system

This study presents the successful synthesis of metal-organic frameworks (MOFs) via a simple one-pot method, followed by pyrolysis at 1000 °C to be used in the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). A study utilizing various techniques, including field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), and X-ray diffraction (XRD), investigated the properties of NiCo-MOF and its individual components before and after pyrolysis.The pristine MOFs exhibited limited electrochemical stability for both ORR and OER, while the pyrolyzed MOFs demonstrated a significant enhancement and excellent long-term stability in OER and ORR performance in alkaline media. Notably, the OER performance rivaled that of the benchmark IrO2 electrocatalyst, with similar onset potentials (1.48 V for IrO2, 1.52 V, 1.56 V, and 1.59 V for pyrolyzed NiCo-MOF, Co-MOF, and Ni-MOF, respectively). Furthermore, the pyrolyzed MOF catalysts displayed promising ORR activity in a 0.1 M KOH solution under O2 saturation, as evidenced by their onset potentials (around 0.615 V, 0.63 V, and 0.7 V vs. RHE) and favorable Tafel slopes (53, 84, and 154 mV dec⁻1, for graphitizated Ni-MOF, Co-MOF, and NiCo-MOF, respectively). These findings demonstrate the effectiveness of pyrolysis in engineering the MOF crystal structure for enhanced catalytic performance. This paves the way for further exploration of this synthesis method for the design of structurally optimized catalysts and applicable to a broad spectrum of energy technologies.

Fe,Ce Co-Doped Ni3S2/NiS Polymorphism Nanosheets with Improved Electrocatalytic Activity and Stability for Water Oxidation.

Balancing the relationship between electrocatalytic activity and stability of sulfide catalysts during oxygen evolution reaction (OER) has been attracting extensive research interest. Here, a simple electrodeposition-vulcanization two-step route was designed to successfully construct nickel foam supported sheet-like Fe,Ce-codoped Ni3S2/NiS polymorphism catalyst (labeled as Fe,Ce-Ni3S2/NiS/NF). Electrochemical measurements showed that the as-obtained Fe,Ce-Ni3S2/NiS/NF electrode presented excellent OER electrocatalytic performances. In 1 M KOH solution, merely 173 and 234 mV of overpotentials were required to deliver the current densities of 10 and 100 mA cm-2, respectively. Further investigations revealed that the Fe,Ce co-doping regulated the electron density around Ni, which promoted the conversion of Ni towards the higher valence state and simultaneously, avoided the stability decrease of the catalyst caused by excessive oxidation corrosion. Moreover, the defects generated during vulcanization also contributed to promoting water oxidation. The present work provides a facile and feasible approach to balance the relationship between the stability and the activity of sulfide catalysts for OER.

Ir-Doped Core-Shell Hollow Heterogeneous Nanospindles for Electrocatalytic Oxygen Evolution Reaction.

By utilizing Metal-organic framework (MOF) materials as a base, constructing electrocatalysts with heterogeneous structures offers advantages for catalyzing water splitting. In this study, a hollow heterogeneous nanocatalyst, Ir-MIL-88A@NiFe-LDHs, was prepared by growing a layered double hydroxides (LDHs) shell on MIL-88A substrate. The catalyst shows excellent oxygen evolution reaction (OER) performance in a 1.0 M KOH solution, requiring only 217 mV overpotential to achieve a current density of 10 mA cm-2 with a Tafel slope of 62.18 mV dec-1, indicating significant electrocatalytic performance and reaction kinetics characteristics. Furthermore, long-term OER testing also demonstrates the catalyst's outstanding stability. Emphasizing the interfacial interaction between MOF and LDHs, as well as the synergistic effect among Ni, Fe, and Ir elements, the study highlights how these factors collaboratively control the local electronic structure of the hollow Ir-MIL-88A@NiFe-LDHs, resulting in an efficient MOF-derived electrocatalyst.

Low-Temperature Plasma-Constructed Ni-Doped W18O49 Nanorod Arrays for Enhanced Electrocatalytic Oxygen Evolution and Urea Oxidation.

Surface engineering by doping and amorphization is receiving widespread attention from the perspective of the regulation of the electrocatalytic activities of electrocatalysts. However, the effective modulation of active sites on catalysts is still challenging. Herein, a straightforward and efficient method combining hydrothermal treatment with low-temperature plasma processing is presented to synthesize Ni-doped W18O49 nanorod arrays on carbon cloth with abundant oxygen vacancies (CC/WO-Ni-x). Mild plasma doping with Ni modifies the electronic structure of the W18O49 nanorod arrays, resulting in the formation of an amorphous structure that significantly reduces the electron transfer resistance. Additionally, the coupling with high-valent W6+ (derived from W18O49) leads to the partial preoxidation of doped Ni to form active Ni3+ species and oxygen vacancies. These features are collectively responsible for the remarkable oxygen evolution reaction (OER) and urea oxidation reaction (UOR) properties of CC/WO-Ni-4, for example, 10 mA cm-2 current density, an overpotential of 265 mV required for the OER under 1.0 M KOH solution. The addition of 500 mM urea to the 1.0 M KOH solution decreases the overpotential required for the same current density from 265 to 93 mV. This study provides insights into the modification of surface structures and presents an effective strategy to optimize the electrocatalytic active sites and enhance the efficiency of multifunctional electrocatalysts.

Enhanced hydrogen evolution reaction activity through samarium-doped nickel phosphide (Ni2P) electrocatalyst

Hydrogen evolution reaction (HER) stands out among conventional hydrogen production processes by featuring excellent advantages. However, the uncompetitive production cost due to the low energy efficiency has hindered its development, necessitating the introduction of cost-effective electrocatalysts. In this study, we introduced samarium doping as a high-potential approach to improve the electrocatalytic properties of nickel phosphide (Ni2P) for efficient HER. Samarium-doped Ni2P was synthesized via a facile two-step vapor–solid reaction technique. Different physical and electrochemical analyses showed that samarium doping significantly improved pure Ni2P characteristics, such as particle size, specific surface area, electrochemical hydrogen adsorption, intrinsic activity, electrochemical active surface area, and charge transfer ability in favor of HER. Namely, Ni2P doped with 3%mol of samarium (Sm0.03Ni2P) with a Tafel slope of 67.8 mV/dec. and overpotential of 130.6 mV at a current density of 10 mA/cm2 in 1.0 M KOH solution exhibited a notable performance, suggesting Sm0.03Ni2P and samarium doping as a remarkable electrocatalyst and promising promoter for efficient HER process, respectively.

Tungsten, copper and cobalt-single metal atom oxides embedded CeO2-MnO2-rGO nanorods as electrocatalysts for efficient oxygen evolution reaction

BackgroundAn important aspect of energy conversion and storage technology is primarily based on the electrocatalytic oxygen evolution process (OER). MethodHere, we present the newly designed synthesis of an improved variety of WCuCo-CeO2-MnO2-R-3 nanocomposites, to enhance OER by incorporating the reduced graphene oxide (rGO), and SMAO of W, Cu, and Co with the nanorods of CeO2-MnO2 materials. Interestingly, the higher density of SMAO (W, Cu, and Co), atomic utilization and electron transfer layer of rGO influenced the CeO2-MnO2 nanorods with remarkably superior electrocatalytic OER activity. Significant findingsThis makes WCuCo-CeO2-MnO2-R-3 achieve 10 mA cm-2 with an overpotential of 275 mV and a lower Tafel slop of 64.46 mV dec‑1. The higher number of SMAO (W, Cu, and Co) species close to the catalyst surface served as potential active sites assembly to enhance the OER activity by improving the chemical and electrochemical steps during the OER process. The chronoamperometry test revealed that the WCuCo-CeO2-MnO2-R-3 nanocomposite is not degrade in a 1 M KOH solution for 24 h, and it is stable up to 2000 CV cycles. In order to create very effective catalysts for OER, the DFT theoretical results shed light on the connection between the catalytic characteristics of metal oxide structures and their inherent electronic configuration.

Poly(Dibenzothiophene-Terphenyl Piperidinium) for High-Performance Anion Exchange Membrane Water Electrolysis.

The anion exchange membrane water electrolysis is widely regarded as the next-generation technology for producing green hydrogen. The OH- conductivity of the anion exchange membrane plays a key role in the practical implementation of this device. Here, we present a series of Z-S-x membranes with dibenzothiophene groups. These membranes contain sulfur-enhanced hydrogen bond networks that link surrounding surface site hopping regions, forming continuous OH- conducting highways. Z-S-20 has a high through-plane OH- conductivity of 182±28 mS cm-1 and ultralong stability of 2650 h in KOH solution at 80 °C. Based on rational design, we achieved a high PGM-free alkaline water electrolysis performance of 7.12 A cm-2 at 2.0 V in a flow cell and demonstrated durability of 650 h at 2 A cm-2 at 40 °C with a cell voltage increase of 0.65 mV/h.

Poly(Dibenzothiophene‐Terphenyl Piperidinium) for High‐Performance Anion Exchange Membrane Water Electrolysis

AbstractThe anion exchange membrane water electrolysis is widely regarded as the next‐generation technology for producing green hydrogen. The OH− conductivity of the anion exchange membrane plays a key role in the practical implementation of this device. Here, we present a series of Z−S‐x membranes with dibenzothiophene groups. These membranes contain sulfur‐enhanced hydrogen bond networks that link surrounding surface site hopping regions, forming continuous OH− conducting highways. Z−S‐20 has a high through‐plane OH− conductivity of 182±28 mS cm−1 and ultralong stability of 2650 h in KOH solution at 80 °C. Based on rational design, we achieved a high PGM‐free alkaline water electrolysis performance of 7.12 A cm−2 at 2.0 V in a flow cell and demonstrated durability of 650 h at 2 A cm−2 at 40 °C with a cell voltage increase of 0.65 mV/h.

Structural Instability of NiFe‐Layered Double Hydroxide Nanosheets during Water Oxidation Operation

AbstractNiFe‐layered double hydroxide (NiFe‐LDH) stands out as a promising electrocatalyst for the oxygen evolution reaction (OER), but the structural transformations under OER conditions are not well understood. The structural evolution of highly crystalline NiFe‐LDH on nickel foam during OER testing in 1 M KOH solution was analyzed using IR, Raman, XRD, XPS techniques, and DFT calculations. Instability of interlayer species within the NiFe‐LDH, including protons, anions, and water molecules, was found to cause the crystal structure to undergo expansion or contraction during OER operation, decreasing crystallinity and roughening the LDH surface. This dynamic structural evolution is crucial for determining OER activity, and it was observed that surface structural changes of the LDH, along with Fe content, jointly determined the degree of change in its OER activity. Our findings provide insights into designing active water‐splitting electrocatalysts and highlight the relationship between OER activity and the structure of NiFe‐LDH.

Molecular and morphological data reveal two new polypores (Polyporales, Basidiomycota) with reddish brown to orange basidiomata from China.

Two taxonomically controversial polypore genera with reddish brown to orange basidiomata that stain reddish with KOH solution, Aurantiporus and Hapalopilus, are revised based on additional sampling, morphological examination, and phylogenetic analysis of a combined dataset of ITS1-5.8S-ITS2-nLSU sequences. Hapalopilus is a monophyletic genus belonging to Phanerochaetaceae, whereas Aurantiporus is a polyphyletic genus belonging to Meruliaceae. Hapalopilus and Aurantiporus s. str. are circumscribed, and two new species - Aurantiporusorientalis and Hapalopilustabuliformis - are described and illustrated from temperate China. In addition, four new combinations, viz. Aurantiporusalboaurantius, A.mutans, A.tropicus and Luteoporiaalbocitrina, are proposed based on morphology and phylogenetic analysis. The relationships between Aurantiporus and Hapalopilus are discussed.

The cobalt-based metal organic frameworks array derived CoFeNi-layered double hydroxides anode and CoP/FeNi2P heterojunction cathode for ampere-level seawater overall splitting

The seawater electrolysis technology powered by renewable energy is recognized as the promising “green hydrogen” production method to solve serious energy and environmental problems. The lack of low-cost and ampere-level current OER (oxygen evolution reaction) and HER (hydrogen evolution reaction) catalysis limits their industrial application. In this work, a unique tri-metal (Co/Fe/Ni) layered double hydroxide hollow array anode catalyst (CFN-LDH/NF) and the CoP/FeNi2P heterojunction hollow array cathode are successfully prepared via one in-situ growth of Co-MOF on nickel foam (Co-MOF/NF) precursor, which exhibits excellent catalytic performance. The η1000 values of 352 and 392 mV are achieved for CFN-LDH/NF (OER catalyst) in 1.0 M KOH and alkaline seawater solution, respectively. The CFNP/NF with a low overpotential of 281 mV is required to reach 1000 mA cm−2 current density for HER in 1.0 M KOH solution, while the η1000 in alkaline seawater solution is 312 mV. The CFN-LDH/NF||CFNP/NF electrolyzer exhibits excellent long-term durability over 100 h, achieving current density of 500 mA cm−2 at 1.825 V in 1.0 M KOH solution. The construction of hollow tri-metal LDH and phosphides heterostructures may open a new and relatively unexplored path for fabricating high performance seawater splitting catalysis.

Dual crosslinked interpenetrating polymer network-based porous hydrogel membrane for solid-state supercapacitor applications

Hydrogel membranes have emerged as promising candidates for solid-state supercapacitors (SSCs), overcoming limitations associated with traditional liquid electrolytes like leakage, thermal hazards, and flammability. However, single-network hydrogels often suffer from poor mechanical properties, making them inadequate for wearable applications. Herein, solution casting technique is used to develop a novel dual-crosslinked semi-interpenetrating polymer network (semi-IPN) hydrogel membrane through in-situ polymerisation of acrylic acid (AA) in a polyvinyl alcohol (PVA) matrix, followed by doping with KOH solution. By adjusting the composition between PVA and AA, the phase separation pathway is controlled, resulting in a homogeneously distributed porous architecture that enhances ion-conductive pathways. The hydrogel exhibited excellent properties, including high ionic conductivity (174 mS cm−1), considerable tensile strength (5 MPa), and significant elongation at break (460 %). Dielectric studies confirmed its significantly improved capacitive behaviour and low conductivity relaxation characteristics. Additionally, the resulting pseudocapacitor assembled with graphite-silvernanowire-polyaniline based composite electrode demonstrated a high specific capacitance (302 F g−1 at 0.2 A g−1) with outstanding capacity retention (75 % up to 500 cycles). Overall, the incorporation of this novel material provides great potential for high-performance SSC applications.

Methanol electrooxidation performance of nickel-modified polyaniline thin films for direct methanol fuel cells

A metal–organic composite thin film composed of polyaniline (PANI) and Ni was prepared and characterized for methanol electrooxidation reaction. First, PANI thin films were electrodeposited on a fluorine-doped tin oxide (FTO) coated glass support in an aqueous acidic solution. Subsequently, the polymer film was modified with Ni particles (FTO/PANI-Ni) by chronoamperometric (CA) technique. The composite film was characterized by structural, morphological and electrocatalytic analyses. X-ray diffraction (XRD) results confirmed the crystallization of Ni according to the cubic structure. Scanning electron microscopy (SEM) images showed that the Ni nanoparticles were uniformly dispersed on the PANI surface. The electrocatalytic performance of the FTO/PANI-Ni composite electrode for the methanol electrooxidation reaction was investigated in 0.5 M KOH solution containing methanol using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronoamperometry (CA) techniques. The effects of temperature and methanol concentration on the methanol electrooxidation performance were also studied. The modified composite catalyst exhibited an electrochemically active surface area of 0.5235 cm2. The presence of Ni nanoparticles on the polymer surface promoted the adsorption of methanol molecules and facilitated the oxidation process, leading to higher current densities and better overall performance. The maximum current density was 14 mA cm-2 and the electrode maintain 68 % of its initial activity even after 200 cycles, indicating that the FTO/PANI-Ni electrode exhibited good stability. The high methanol oxidation performance of the composite electrode was associated with large real surface area, a possible synergistic effect between the polymer moleucles and Ni particles as well as high intrinsic activity of Ni for this process.

Stimulating Electron Delocalization of Lanthanide Elements through High-Entropy Confinement to Promote Electrocatalytic Water Splitting.

High-entropy alloys (HEAs) have aroused extensive attention in the field of catalysis. However, due to the integration of multiple active sites in HEA, it exhibits excessive adsorption behavior resulting in difficult desorption of active species from the catalyst surfaces, which hinders the catalytic efficiency. Therefore, adjusting the adsorption strength of the active site in HEA to enhance the catalytic activity is of great importance. By introducing rare-earth (RE) elements into the high-entropy alloy, the delocalization of 4f electrons can be achieved through the interaction between the multimetal active site and RE, which benefits to regulate the adsorption strength of the HEA surface. Herein, the RE Ce-modified hexagonal-close-packed PtRuFeCoNiZn-Ce/C HEAs are synthesized and showed an excellent electrocatalytic activity for hydrogen evolution reaction and oxygen evolution reaction with ultralow overpotentials of 4, 7 and 156, 132 mV, respectively, to reach 10 mA cm-2 in 0.5 M H2SO4 and 1.0 M KOH solutions, and the assembled water electrolysis cell only requires a voltage of 1.43 V to reach 10 mA cm-2, which is much better than the performance of PtRuFeCoNiZn/C. Combined with the results of in situ attenuated total reflection infrared spectroscopy and density functional theory (DFT), the fundamental reasons for the improvement of catalyst activity come from two aspects: (i) local lattice distortion of HEA caused by the introduction of RE with large atomic radius induces 4f orbital electron delocalization of RE elements and enhances electron exchange between RE and active sites. (ii) The electronegativity difference between the RE element and the active site forms a surface dipole in HEA, which optimizes the adsorption of the active intermediate by the HEA surface site. This study provides an insightful idea for the rational design of high-performance HEA- and RE-based electrocatalysts.

Phase-controlled synthesis of starch-derived Mo2C–MoC/C heterostructure catalyst for electrocatalytic hydrogen evolution reaction

The electronic structure of molybdenum carbide closely resembles that of Pt, making it a promising candidate material for replacing noble metal catalysts. However, the primary challenge is the controlled and eco-friendly synthesis of molybdenum carbide. Herein, we developed a sustainable and controlled method for synthesizing a heterostructure catalyst for the electrocatalytic hydrogen evolution reaction (HER) using starch as the raw material. Through a hydrothermal redox reaction and subsequent temperature-programmed treatment under an inert atmosphere, the hexagonal Mo2C-cubic MoC heterostructure nanoparticles were dispersed on a carbon matrix. Our investigation into the synthesis process extensively covered the growth of MoO2 nanocrystals and hydrochar during the hydrothermal redox reaction, as well as the phase evolution during the subsequent temperature-programmed treatment. Electrochemical assessments demonstrated the catalyst's remarkable efficiency for the hydrogen evolution reaction across both acidic and alkaline media, achieving a current density of 10 mA/cm2 with an overpotential of 139.4 mV in 1 M KOH solution and 160.7 mV in 0.5 M H2SO4 solution. Combining a series of electrochemical characterizations and applying the distribution of relaxation times (DRT) analysis to operando electrochemical impedance spectroscopy (EIS) data, the superior kinetic performance of the Mo2C–MoC/C was demonstrated, outperforming that of single-phase molybdenum carbide. Furthermore, the catalyst has demonstrated remarkable stability even at high current densities in both acidic and alkaline electrolytes, underscoring its potential as a cathode catalyst in both alkaline water electrolyzers and proton exchange membrane (PEM) electrolyzers.

Two-Dimensional NiCo2S4 Nanosheets Deliver Efficient Oxygen Evolution Reaction

Introduction: The development of cost-effective and efficient catalysts plays a pivotal role in the realization of hydrogen production through electrochemical water splitting. Method: In this study, two-dimensional NiCo2S4 nanosheets weresynthesized usinga hydrothermal method followed by a sulfidation process. Results: The resulting materials were thoroughly characterized to understand their morphology and structure. The findings indicate that the NiCo2S4 nanosheets exhibit exceptional electrical conductivity and a high density of pores, which facilitate electrolyte infiltration and interfacial charge transfer during electrochemical reactions. Furthermore, the incorporation of S2− modulates the electronic structure of metal ions, reducing the oxidation potential of metal sites and promoting the surface reconstruction of the electrode to form active species. Electrochemical tests conducted in a 1 M KOH solution using the synthesized catalyst as the working electrode demonstrate an overpotential of merely 280 mV and 300 mV at a current density of 20 mA cm−2 and 40 mA cm−2 , respectively, which are much lower than those of NiCo-LDH electrodes (360 mV and 410 mV). Conclusion: Furthermore, the NiCo2S4 electrode delivers a remarkably low Tafel slope of 47.9 mV dec−1 . This investigation presents a novel approach to the development of efficient transition metal-based electrocatalysts.

In situ growth of NiMoO4-C nanocomposite and electrodeposition of multi-metal selenide to enhance oxygen evolution efficiency in alkaline solution

This study primarily centers on the fabrication of NiMoO4-C@Ni(FeMo)-Se composite electrocatalysts directly onto nickel foam substrates through a hydrothermal followed by electrodeposition technique. Through this method, the carbon submicron sphere structure, interlinked by NiMoO4 nanorods, undergoes further optimization, resulting in a more refined NiMoO4-C@Ni(FeMo)-Se core-shell structure. The NiMoO4-C@ Ni(FeMo)-Se /NF composite electrode exhibited exceptional OER catalytic activity in a 1 M KOH solution, with an overpotential of merely 228 mV at a current density of 50 mA·cm−2 and a Tafel slope of 35.9 mV·dec−1, significantly superior to that of the blank NF. Additionally, a 40-hour stability test at a current density of 50 mA·cm−2 demonstrated that the potential remained nearly constant, highlighting the exceptional OER activity and long-term stability of the synthesized catalyst. Moreover, in the overall water splitting process, the utilization of a dual-electrode NiMoO4‐C@Ni(FeMo)‐Se/NF||Pt‐C/NF electrolytic cell demands a remarkably low potential of 1.48 V to achieve a current density of 10 mA·cm−2, demonstrating exceptional electrocatalytic activity and long-term stability. Therefore, this study provides a promising route for the application of hydrogen production from alkaline aqueous solutions.

Electrochemical Investigation of ZnS/NiO Nanocomposite based Symmetric Supercapattery

AbstractSupercapattery is an ideal energy storage device combining the features of supercapacitors and batteries, offers a high‐energy density as well as high‐power density with extended operational lifespan. In this work, zinc sulfide (ZnS) and zinc sulfide/nickel oxide (ZnS/NiO) nanocomposite was synthesized via chemical coprecipitation method and characterized using state‐of‐the‐art analytical tools. The ZnS/NiO electrode exhibited remarkable electrochemical performance as an electrode material than pure ZnS. The ZnS/NiO nanocomposite exhibited high crystallinity, and spherical nanoparticles with an average grain size of 20–40 nm having a homogeneous dispersion. The ZnS/NiO electrode exhibited an ultrahigh specific capacity of 1803.87 Cg−1 at a relatively low scan rate of 10 mVs−1 in a 1 M KOH solution from cyclic voltammetry and 393 Cg−1 at 16 Ag−1 from charge discharge measurements, and it showed exceptional cycling stability (98 % capacity retention after 1000 cycles). Furthermore, the ZnS/NiO symmetric supercapattery device exhibited 44.43 Fg−1 specific capacitance, 5.52 Wh kg−1 energy density, and 1600 Wkg−1 power density at current density of 0.8 Ag−1 in 1 M KOH solution from galvanostatic charge discharge. After 3000 cycles, the ZnS/NiO nanomaterial demonstrated promising cyclic stability of 95 %. The ZnS/NiO supercapattery nanocomposite might be considered as a potential hybrid electrode material for the future development of electrochemical energy storage devices.

Europium Oxide Evoked Multisite Synergism to Facilitate Water Dissociation for Alkaline Hydrogen Evolution

AbstractExploring an efficient nonnoble metal catalyst for hydrogen evolution reaction (HER) is critical for industrial alkaline water electrolysis. However, it remains a great challenge due to the additional energy required for H─OH bond cleavage and the lack of enough H2O adsorption sites for most catalysts. Herein, the integration of oxophilic Eu2O3 with NiCo alloy with evoked multisite synergism to facilitate water dissociation for alkaline HER is proposed. The optimized Eu2O3‐NiCo exhibits excellent HER activity with a low overpotential of only 60 mV at 10 mA cm−2 and good electrochemical stability, which is superior to that of Eu2O3‐free NiCo and comparable to benchmark Pt/C. The key roles of Eu2O3 on the enhanced HER performance of Eu2O3‐NiCo are identified by in situ Raman spectroscopy and theoretical calculations. It is discovered that the Eu2O3 with strong oxophilicity facilitates the adsorption of H2O and the breakage of H─OH bonding while evoking the electron redistribution at Eu2O3/NiCo interface and accelerating the Volmer step in alkaline HER. Furthermore, the obtained Eu2O3‐NiCo as both anode and cathode displays excellent overall water‐splitting activity and stability in 1.0 M KOH solution. It is believed that this study provides an important inspiration to design high‐performance electrocatalysts toward HER based on rare‐earth materials.