Electrochemical Hydrogen Evolution Research Articles

Ni-Ti3C2 MXene composite derived from Ni-metal organic framework for electrochemical hydrogen evolution reaction in acidic and alkaline medium

MOFs derived metal composites are found to be a potential electrocatalyst for energy storage and conversion process. In this work, Ni composite with MXene (Ni-Ti3C2) was synthesized by calcination of Ni-MOF at 650 °C and characterized by XRD, FE-SEM, FTIR and BET analysis. After calcination, the derived Ni composited Ti3C2 showed a high porosity and high surface area as compared to Ti3C2. The derived material was further used as electrode for Hydrogen Evolution Reaction (HER) and tested by various electrochemical analysis viz. Cyclic voltammetry (CV), Electrochemical impedance analysis (EIS) and Linear Sweep Voltammetry (LSV) in alkaline medium. The derived Ni-Ti3C2 in basic medium displays a small Tafel value of 56.15 mV/dec with acquired voltage of 181.15 mV due to the surface area and accessible catalytic active sites, which provides excellent mass transfer properties for derived Ni-Ti3C2 composite in basic medium. The kinetics of the HER reaction was found better in Ni-Ti3C2 MXene composite in basic medium than in acidic medium. The charge transfer resistances were obtained from the EIS plot and were found to be 3.98 Ω and 2.34 Ω for Ti3C2 and Ni-Ti3C2 respectively in acidic medium and 3.12 Ω and 1.98 Ω in basic medium. The low resistance observed for Ni-Ti3C2 in basic medium proves a higher electrocatalytic activity in Ni-Ti3C2 than Ti3C2. The cyclic stability of the Ni-Ti3C2 in basic medium was higher than Ti3C2. Thus the overall results show that the prepared composite is a potential catalyst for HER applications.

Defect-rich 1T-MoS2 nanosheets towards efficient electrochemical hydrogen evolution by simultaneous phase and defect engineering

Molybdenum sulfide (MoS2) has been considered as a promising candidate to replace Pt for the electrochemical hydrogen evolution reaction (HER). However, the disadvantages of inert basal planes and low conductivity limit its application in HER. Herein, we report a facile strategy to achieve simultaneous phase transition and defect engineering in MoS2 by adjusting the ratio of sulfur precursor to molybdenum precursor in the synthesis process. The excess thiourea are adsorbed on the surface of as-formed MoS2 nanocrystallites, which hinders the further crystallization process and creates a large amount of defects on the basal planes. Besides, ammonia ions could in situ insert into the interlayers of MoS2 and induce a phase transition from 2H–MoS2 to 1T-MoS2. The optimized defect-rich 1T-MoS2 catalyst shows a small overpotential of 232 mV at 10 mA cm−2 and Tafel slope of 61 mV dec−1 in acidic media. The superior HER activity is attributed to the defect-rich and 1T-phase structure, which contributes significantly enhanced electronic conductivity and greatly exposed active sites.

Modulating Force of Nucleated Hydrogen Bubble Adhesion to Boost Electrochemical Water Splitting

AbstractIn electrochemical hydrogen evolution reaction (HER), the produced hydrogen gas bubbles often adhered to the electrode surface and blocked the active catalytic site. While different catalysts are developed to improve the catalytic performance of HER, the design of a durable and universal approach for minimizing the force of nucleated hydrogen gas‐bubble adhesion to prevent blockage of electrocatalytic sites because of bubbles‐adhesion is unprecedented. Generally, buoyancy should outweigh the capillary force to remove nucleated bubbles, which means these forces ratio, Eötvös number Eo > 1. Herein, a chemically reactive multilayer coating on an electrode is reported to chemically modulate the adhesion force of nucleated gas‐bubble on the electrode. A dual modified coating on Ni‐foam provided a non‐adhesive superaerophobicity with nucleated bubble adhesion force of 4.6 ± 0.3 µN and displayed superior HER performance with lower overpotential (333 to 250 mV) at 100 mA cm−2 with respect to bare Ni‐foam. The chemically‐modulated low bubble‐adhesion facilitates the early removal of nucleated tiny hydrogen gas bubbles with a minimum size of 0.64 mm and Eo = 0.05 to keep catalytic sites available for superior electrochemical HER. Such a positive impact of the prepared coating is also noted for various other electrodes.

ΜοS2 nanoensembles prepared by a simple solvothermal route for hydrogen evolution reaction

Electrochemical hydrogen evolution reaction (HER) is an emerging research domain aiming to supply a means of renewable energy. Transition metal dichalcogenides (TMDs) have a good potential as promising low-cost alternatives to platinum-based catalysts. Molybdenum disulfide (MoS2) nanostructures with different shapes are increasingly becoming attractive materials for HER electrocatalysis, thanks to their peculiar physical properties which depend on their composition and morphology. It is still challenging to produce MoS2 nanomaterials simply and straightforwardly. In this work, MoS2 nanoensembles and small nanoparticles were fabricated via facile solvothermal protocols. The produced structures display a competitive activity in HER, with the nanoensembles performing better than the isotropic particles. This was attributed to the abundance of their electrochemically active sites and their robust structural stability, which endowed them with remarkable endurability in electroactivity. The nanoensemble morphology ensured the creation of a well-connected array of channels for charge transport, thus favouring an ameliorated electrochemical activity.

Shape and Phase-Controlled One-Pot Synthesis of Air Stable Cationic AgCdS Nanocrystals, Optoelectronic and Electrochemical Hydrogen Evolution Studies.

CdS-based materials are extensively studied for photocatalytic water splitting. By incorporating Ag+ into CdS nanomaterials, the catalyst's charge carrier dynamic can be tuned for photo-electrochemical devices. However, photo-corrosion and air-stability of the heterostructures limit the photocatalytic device's performance. Here, a one-pot, single molecular source synthesis of the air-stable AgCdS ternary semiconductor alloy nanostructures byheat-up method is reported. Monoclinic and hexagonal phases of the alloy are tuned by judicious choice of dodecane thiol (DDT), octadecyl amine (ODA), and oleyl amine (OLA) as capping agents. Transmission electron microscope (TEM) and powder X-ray diffraction characterization of the AgCdS alloy confirm the monoclinic and hexagonal phase (wurtzite) formation. The high-resolution TEM studies confirm the formation of AgCdS@DDT alloy nanorods and their shape transformation into nano-triangles. The nanoparticle coalescence is observed for ODA-capped alloys in the wurtzite phase. Moreover, OLA directs mixed crystal phases and anisotropic growth of alloy. Optical processes in AgCdS@DDT nano-triangles show mono-exponential decay (3.97 ± 0.01ns). The monoclinic phase of the AgCdS@DDT nanorods exhibits higher electrochemical hydrogen evolution activity in neutral media as compared to the AgCdS@ODA/OLA alloy nanocrystals. DDT and OLA-capped alloys display current densities of 14.1 and 14.7mA cm-2 , respectively, at 0.8V (vs RHE).

Electrochemical Hydrogen Evolution Reaction Evaluation of CoNi(Cr/V) Medium-Entropy Alloys in an Acidic Environment

Electrochemical Hydrogen Evolution Reaction Evaluation of CoNi(Cr/V) Medium-Entropy Alloys in an Acidic Environment

Strain and Shell Thickness Engineering in Pd3 Pb@Pt Bifunctional Electrocatalyst for Ethanol Upgrading Coupled with Hydrogen Production.

The ethanol oxidation reaction (EOR) is an attractive alternative to the sluggish oxygen evolution reaction in electrochemical hydrogen evolution cells. However, the development of high-performance bifunctional electrocatalysts for both EOR and hydrogen evolution reaction (HER) is a major challenge. Herein, the synthesis of Pd3 Pb@Pt core-shell nanocubes with controlled shell thickness by Pt-seeded epitaxial growth on intermetallic Pd3 Pb cores is reported. The lattice mismatch between the Pd3 Pb core and the Pt shell leads to the expansion of the Pt lattice. The synergistic effects between the tensile strain and the core-shell structures result in excellent electrocatalytic performance of Pd3 Pb@Pt catalysts for both EOR and HER. In particular, Pd3 Pb@Pt with three Pt atomic layers shows a mass activity of 8.60 A mg-1 Pd+Pt for ethanol upgrading to acetic acid and close to 100% of Faradic efficiency for HER. An EOR/HER electrolysis system is assembled using Pd3 Pb@Pt for both the anode and cathode, and it is shown that low cell voltage of 0.75V is required to reach a current density of 10mA cm-2 . The present work offers a promising strategy for the development of bifunctional catalysts for hybrid electrocatalytic reactions and beyond.

Aminosilanized Interface Promotes Electrochemically Stable Carbon Nitride Films with Fewer Trap States on FTO for (Photo)electrochemical Systems.

We have demonstrated the direct growth of a CNx layer on a plasma-cleaned and aminosilanized F-doped SnO2 (FTO) electrode to study the CNx|FTO interface that is critical for (photo)electrocatalytic systems. The (3-aminopropyl)triethoxysilane (APTES) was chosen as a bifunctional organosilane, with the amino end incorporating into CNx and the silane end connecting to the hydroxylated FTO surface. Plasma cleaning and aminosilanization resulted in a highly hydrophilic surface, which leads to better contact of melted thiourea to the aminosilanized FTO (p-FTONH2) during CNx polymer condensation, thus generating a thinner and more compact CNx layer. The modification at the interface was shown to influence the CNx growth on length scales of tens of micrometers. We grew CNx thin films on p-FTONH2 (CNx/p-FTONH2) and nonaminosilanized p-FTO (CNx/p-FTO). CNx/p-FTONH2 had a smaller density of trap states and passed 2.4 times the charges before failure compared to CNx/p-FTO. Additionally, a 40% decrease in interfacial charge transfer resistance at the CNx|electrolyte interface was measured for CNx/p-FTONH2 compared to CNx/p-FTO under -0.5 V vs RHE in 0.1 M Na2SO4. Furthermore, with the CNx surface coated with a Pt cocatalyst, Pt/CNx/p-FTONH2 exhibited faster hydrogen evolution rates and larger current densities than Pt/CNx/p-FTO. The highest Faraday efficiency toward electrochemical hydrogen evolution (FEH2) in 0.1 M Na2SO4 (pH = 7) was 46.1%, 37.3%, 57.7%, and 70.5% for Pt/CNx/p-FTONH2, Pt/CNx/p-FTO, CNx/p-FTONH2, and CNx/p-FTO, respectively. The increase in hydrogen evolution rate did not follow the magnitude of the current density change, indicating electrochemical processes other than proton reduction. Overall, we have carefully investigated the CNx|FTO interface and suggested potential solutions to make CNx films better (photo)electrodes for (photo)electrochemical systems.

A general protocol for precise syntheses of ordered mesoporous intermetallic nanoparticles.

Intermetallic nanomaterials consist of two or more metals in a highly ordered atomic arrangement. There are many possible combinations and morphologies, and exploring their properties is an important research area. Their strict stoichiometry requirement and well-defined atom binding environment make intermetallic compounds an ideal research platform to rationally optimize catalytic performance. Making mesoporous intermetallic materials is a further advance; crystalline mesoporosity can expose more active sites, facilitate the mass and electron transfer, and provide the distinguished mesoporous nanoconfinement environment. In this Protocol, we describe how to prepare ordered mesoporous intermetallic nanomaterials with controlled compositions, morphologies/structures and phases by a general concurrent template strategy. In this approach, the concurrent template used is a hybrid of mesoporous platinum or palladium and Korea Advanced Institute of Science and Technology-6 (KIT-6) (meso-Pt/KIT-6 or meso-Pd/KIT-6) that can be transformed by the second precursors under reducing conditions. The second precursor can either be a second metal or a metalloid/non-metal, e.g., boron/phosphorus. KIT-6 is a silica scaffold that is removed using NaOH or HF to form the mesoporous product. Procedures for example catalytic applications include the 3-nitrophenylacetylene semi-hydrogenation reaction, p-nitrophenol reduction reaction and electrochemical hydrogen evolution reaction. The synthetic strategy for preparation of ordered mesoporous intermetallic nanoparticles would take almost 5 d; the physical characterization by electron microscope, X-ray diffraction and inductively coupled plasma-mass spectrometry takes ~2 days and the function characterization depends on the research question, but for catalysis it takes 1-5 h.

Facile and Cost-effective Synthesis of CoP@N-doped Carbon with High Catalytic Performance for Electrochemical Hydrogen Evolution Reaction.

The manufacture of efficient and low-cost hydrogen evolution reaction (HER) catalysts is regarded as a critical solution to achieve carbon neutrality. Herein, we developed an economical method to synthesize a CoP-anchored N-doped carbon catalyst via one-step pyrolysis using inexpensive starting materials (cobalt ion salt, phytic acid, and glycine). The size of the CoP nanoparticles was controlled by adjusting the Co/P ratio of the catalysts. Nanoscale CoP particles with adequate exposure to active sites were uniformly anchored on the surface of the conductive nitrogen-doped carbon substrate, ensuring the rapid transfer of electrons and species. When Co/P=0.89, the as-made catalyst exhibited outstanding HER activity, with an extraordinarily low overpotential of 202 mV at 10 mA cm-2 and long-term stability.

Highly active Mo-modified NiCoP/NiCoN flower-like sphere: Controlled phase engineering for efficient water splitting

Reasonable design and preparation of a versatile catalyst for the ultra-high efficiency energy conversion system has remarkable practical significance. Herein, a facile phase engineering strategy is employed to synthesize molybdenum modified nickel cobalt nitride and nickel cobalt phosphide flower-like sphere heterostructure (labeled as Mo-NiCoP/NiCoN FS) to improve the performance of Mo-NiCoN FS. The significant geometric structure advantages, the exposure to abundant active centers and the interfacial effect of heterostructure of the target product is evaluated in detail. When the as-obtained Mo-NiCoP/NiCoN FS is applied to the electrochemical bifunctional hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), it demonstrates remarkable electrocatalytic activity, high-conductivity and excellent corrosion resistance compared with Mo-NiCoN FS with a single phase. As a result, Mo-NiCoP/NiCoN FS indicates a low overpotential towards HER (204 mV at 10 mA/cm2) and OER (262 mV at 10 mA/cm2) compared with Mo-NiCoN (234 mV for HER and 357 mV for OER at 10 mA/cm2) in an alkaline medium and it exhibits excellent activity and stability during the dual-electrode full water-splitting. Therefore, the advanced nano-catalyst with superior activity developed through the controllable phase engineering method illustrates a potential application prospect in high efficiency energy equipment water-splitting and fuel-cells.

Alkynyl-protected Ag20 Rh2 Nanocluster with Atomic Precision: Structure Analysis and Tri-functionality Catalytic Application.

We report the overall structure and trifunctionality catalytic application of an atomically precise alloy nanocluster of Ag20 Rh2 (C≡C-t Bu)16 (CF3 CO2 )6 (H2 O)2 (abbreviated as Ag20 Rh2 hereafter). Ag20 Rh2 has a twisted rod-like structure, where a Ag4 @Rh2 kernel is connected by two twisted Ag8 cubes on two sides. Ag20 Rh2 is a superatomic cluster with four free valence electrons, and it has characteristic absorbance feature. Interestingly, Ag20 Rh2 exhibited superior catalytic performance than the larger AgRh nanoparticle counterparts in electrochemical hydrogen evolution reaction (HER), reduction of 4-nitrophenol, and the methyl orange degradation reaction. Such intriguing catalytic properties are attributed to the more exposed active sites from the ultrasmall nanoclusters than relatively large nanoparticles. This study not only enriches the family member of alkynyl-protected AgRh nanoclusters with atomic precision, but also highlights the great advantages of employing nanoclusters as efficient catalysts for multiple functionalities.

Catalytic properties and stability of nickel–tin powder alloys in the process of electrochemical hydrogen evolution from alkali solution

Ni–Sn powder alloys with a nickel content from 24.4 to 78.5 at.% and from 30.6 to 55.1 at.%, respectively, were synthesized chemically and electrochemically for the use as catalysts for the hydrogen electrochemical reduction (HER) in alkali solution. It was established that the catalytically active surface area of chemically synthesized powders was larger in comparison with electrochemically obtained ones. Ni24.4Sn75.6 powder alloy has the largest surface area. It was found that catalytic properties of chemically synthesized powders increased in the row Ni24.4Sn75.6 < Ni78.5Sn21.5 < Ni. Electrochem ically obtained alloys are inefficient as HER catalysts. It was found that Ni24.4Sn75.6 alloy is characterized by the greater re tention of catalytically active surface area during exploitation in alkali solution in comparison with Ni and Ni78.5Sn21.5 alloy.

Re-Structuring of Interfacial Water into Strongly Hydrogen Bonded “Ice-like” Structures as the Unifying Descriptor for Improving Sluggish HOR/HER in Alkaline Electrolyte

The 2 orders of magnitude loss of Platinum Group Metal (PGM) activity toward Hydrogen Oxidation and Reduction reactions (HOR/HER) has hindered implementation of alkaline based electrolyzers and fuel cells and demonstrated a significant knowledge gap in our fundamental understanding of electrochemical interfaces.1 Beneath the seemingly simple reaction lies a potentially convoluted mechanism, with various researchers assigning the activity loss to shifts in electrode potential of zero free charge,2 changed binding energies of adsorbates and reactive intermediates,3,4 and the re-arrangement of interfacial water.5 Recently, Monteiro et al. showed an activity dependence on interfacial cation concentration and identity, suggesting that charge dense cations are able to better stabilize the OH- produced from the unfavorable but necessary water splitting in the HER direction near the negatively charged surface.6,7 In this work, we challenge this notion by demonstrating that competition for water molecules between Outer Helmholtz Plane (OHP) cations and the interfacial water structure is responsible for the activity loss. Through the use of traditional Rotating Disk Electrode, in situ Attenuated Total Reflection-Surface Enhanced Infrared Reflection Absorption Spectroscopy (ATR-SEIRAS) and judicious choice of crown ether additives to hinder the water-interfacial cation interaction, we show a positive correlation between the strength and number of interfacial water-water hydrogen bonds and platinum’s HOR/HER activity.The typical double layer structure in an aqueous electrochemical system consists of specifically adsorbed species in the Inner Helmholtz Plane (IHP), the first layer of non-adsorbates at the OHP, and water hydrating the charged species. ATR-SEIRAS has previously been used to analyze the structure of these hydration shells on a CO covered Pt surface, demonstrating hydrating waters interacting mainly with alkali metal cations through the increase of a 3600 cm-1 ν(O-H) stretch and weak interactions with surrounding interfacial water.8 Through chelation with crown ether, these hydration shells convert from strongly to weakly cation interacting, favoring instead hydrogen bonding with other water molecules, shown with increasing absorption bands at lower wavenumbers (3400 cm-1). This transition is accompanied by an increase in 3000 cm-1 on the CO-free Pt surface, previously assigned to strongly hydrogen bonded “ice-like” interfacial water.9 We further show a similar increase in the 3000 cm-1 band for other kinetic enhancing additives recently reported in the literature, supporting the notion that increasing water-water hydrogen bonding is the unifying descriptor for promoting a rigid interfacial “ice-like” structure and improving PGM HOR/HER activity. Durst, J. et al. New insights into the electrochemical hydrogen oxidation and evolution reaction mechanism. Energy Environ. Sci. 7, 2255–2260 (2014).Sarabia, F. J., Sebastián-Pascual, P., Koper, M. T. M., Climent, V. & Feliu, J. M. Effect of the Interfacial Water Structure on the Hydrogen Evolution Reaction on Pt(111) Modified with Different Nickel Hydroxide Coverages in Alkaline Media. ACS Appl. Mater. Interfaces 11, 613–623 (2019).McCrum, I. T. & Koper, M. T. M. The role of adsorbed hydroxide in hydrogen evolution reaction kinetics on modified platinum. Nat. Energy 5, 891–899 (2020).Yang, X., Nash, J., Oliveira, N. J., Yan, Y. & Xu, B. Understanding the pH Dependence of Underpotential Deposited Hydrogen on Platinum. Angew. Chemie - Int. Ed. 58, 17718–17723 (2019).Zhao, K. et al. Enhancing Hydrogen Oxidation and Evolution Kinetics by Tuning the Interfacial Hydrogen-Bonding Environment on Functionalized Platinum Surfaces. Angew. Chemie - Int. Ed. 61, (2022).Monteiro, M. C. O., Goyal, A., Moerland, P. & Koper, M. T. M. Understanding Cation Trends for Hydrogen Evolution on Platinum and Gold Electrodes in Alkaline Media. ACS Catal. 11, 14328–14335 (2021).Goyal, A. & Koper, M. T. M. The Interrelated Effect of Cations and Electrolyte pH on the Hydrogen Evolution Reaction on Gold Electrodes in Alkaline Media. Angew. Chemie - Int. Ed. 60, 13452–13462 (2021).Yamakata, A. & Osawa, M. Cation-dependent restructure of the electric double layer on CO-covered Pt electrodes: Difference between hydrophilic and hydrophobic cations. J. Electroanal. Chem. 800, 19–24 (2017).Osawa, M., Tsushima, M., Mogami, H., Samjeské, G. & Yamakata, A. Structure of water at the electrified platinum-water interface: A study by surface-enhanced infrared absorption spectroscopy. J. Phys. Chem. C 112, 4248–4256 (2008). Figure 1

Enhancing Effect of Boron-Doping on the Activity of Nife-MOF-74 Towards Oxygen Evolution Reaction in Alkaline

Water splitting has drawn significant attention due to the capability of mass-producing hydrogen, which is considered a promising alternative to fossil fuels in the future.[1] The development of electrochemical energy conversion and storage technologies, such as water electrolyzers, metal-air batteries, and regenerative fuel cells, is of great importance to support the transition to clean and renewable energy.[2] Based on the merits of high surface area, 3D periodic porous structure, large porosities, diverse composition and well-defined metal centers, metal–organic frameworks (MOFs) and their derivatives have been widely exploited as OER electrocatalysts.[3]However, MOFs have some limitation to be used as a OER catalysts, considering their poor stabilities (in water, especially basic/acidic conditions) and low electrical conductivities. Incorporation of boron atoms into an aromatic carbon framework offers a wide variety of functionalities. [4] In this work, the flower-like bimetallic NiFe-MOF-74 dopped with boron were fabricated, and they exhibit superior catalytic activity with a very low overpotential of 318 mV for OER at a laboratory grade current density of 10 to 100 mA/cm2 and fast reaction kinetics with a small Tafel slope of 89 mV dec-1 in 1.0 M KOH using a catalyst fabrication process that is scalable to commercial levels. Additional work is required to demonstrate current densities at commercial levels. Reference [1] L. Fan, Z. Kang, M. Li, D. Sun, Recent progress in pristine MOF-based catalysts for electrochemical hydrogen evolution, oxygen evolution and oxygen reduction, Dalton Trans. 50 (2021) 5732–5753. https://doi.org/10.1039/D1DT00302J.[2] Bimetallic metal–organic frameworks and MOF-derived composites: Recent progress on electro- and photoelectrocatalytic applications - ScienceDirect, (n.d.). https://www.sciencedirect.com/science/article/pii/S0010854521005385 (accessed April 27, 2022).[3] J. Du, F. Li, L. Sun, Metal–organic frameworks and their derivatives as electrocatalysts for the oxygen evolution reaction, Chem. Soc. Rev. 50 (2021) 2663–2695. https://doi.org/10.1039/D0CS01191F.[4] Y. Xie, Z. Meng, T. Cai, W.-Q. Han, Effect of Boron-Doping on the Graphene Aerogel Used as Cathode for the Lithium–Sulfur Battery, ACS Appl. Mater. Interfaces. 7 (2015) 25202–25210. https://doi.org/10.1021/acsami.5b08129.

Hydrothermal synthesis of rGO/ZnCoS composite for high performance asymmetric supercapacitor and HER applications

Here, we describe the successful hydrothermal synthesis of zinc cobalt sulfide (ZCS) and reduced graphene oxide/zinc cobalt sulfide (rZCS) nanoparticles (NPs). X-Ray diffraction (XRD), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (TEM) characterizations were used to test ZCS and rZCS NPs. Through the use of cyclic voltammetry (CV), galvanostatic charge and discharge (GCD), and electrochemical impedance (EIS), the electrochemical performance of the produced materials was examined. Electrochemical hydrogen evolution reactions and supercapacitor applications required the development of ZCS and rZCS electrodes. 10 mA cm−2 is driven by rZCS electrodes at 132 mV HER overpotential. High specific capacitance of 891 F g−1 at 1 A g−1 current density and 99 % cyclic stability are displayed by the rZCS electrode even after 5000 cycles. The specific capacitance of (181 F g−1 at 1 A g−1 current density), capacitance retention of (92 % after 10,000 cycles at 1 A g−1, and energy and power density of (29 Wh kg−1 and 2215 W kg−1), respectively, are recommended for asymmetric supercapacitors made from cells using rZCS and rGO. Given this, the produced electrodes material holds potential for use in energy storage technologies.

Variation of dithiolate bridges in carbon nanotube-attached diiron chelate compounds for electrocatalytic hydrogen evolution reaction

In an effort to explore the effect of dithiolate bridges on the electrochemical hydrogen evolution reaction (HER) performances of hydrogenase-inspired catalysts under fully aqueous condition, three new diphosphine-chelate diiron molecular compounds [Fe2(μ-xdt)(CO)4(k2-(Ph2PCH2)2N(CH2CH2OH)] (labeled as 1xdt, xdt = (SCH2)2X, X = NPh (adt) vs. O (odt) vs. CH2 (pdt)) with various dithiolate bridges (i.e., xdt) were prepared and then are covalently attached onto carbon nanotubes (CNTs) to fabricate biomimetic CNT-attached hybrid catalysts labeling as CNT-f-1xdt. The intact structures of target catalysts CNT-f-1xdt have been evidenced through Raman, X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV). Further, the electrochemical HER properties and stabilities of CNT-f-1xdt loaded onto glassy carbon electrode (GC) are studied and compared in 0.05 M phosphate buffer solution (PBS, pH of 7.4) as neutral aqueous medium by using CV, linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), and chronopotentiometry. In comparison with homologues CNT-f-1odt or CNT-f-1pdt containing odt or pdt bridges, the hybrid catalyst CNT-f-1adt bearing an adt bridge is found to have the better electrocatalytic HER activity and similar stability in 0.05 M PBS. This work is significant to develop a promising generation of CNT-attached electrode materials engineered with diiron-based molecular HER catalysts for water splitting into H2.

Rational design of a membrane-coated cathode for selective electrochemical hydrogen evolution in chlorate electrolysis

The industrial chlorate process has traditionally used chromium(VI) as an electrolyte additive for high Faraday efficiency. However, due to its recognized toxicity and carcinogenic properties, the EU has regulated its usage, prompting the need for alternative approaches. In this study, we propose the adoption of a polymeric membrane-coated cathode (MCC) as a straightforward yet highly efficient solution to enhance the selectivity of the hydrogen evolution reaction (HER) in chlorate electrolysis. Proof-of-concept MCCs were fabricated by coating roughened titanium substrates with cation and anion exchange membrane layers, which function as selective barriers for anodic hypochlorite species. The study revealed that a thin membrane coating on the electrode surface effectively suppressed the permeation of anodic intermediates, without compromising the current density for HER. By optimizing the coating layer thickness and substrate surface properties of MCC, the chlorate electrolysis cell demonstrated an impressive Faradaic efficiency of up to 95% at a current density of 150 mA/cm², while maintaining exceptional stability. The outcome of this study can potentially advance the feasibility of industrial chlorate production in meeting regulatory requirements and effectively mitigating environmental consequences.

Electrolytic Hydrogen Evolution Study of Porous Tungsten Carbide‐Loaded Pt Derived from ZIFs

AbstractThe development of an electrochemical hydrogen evolution catalyst with high activity and low Pt loading and excellent stability is of high significance for the extensive promotion and practical application of hydrogen energy. Hence, we introduced ZIFs and their derivatives with tunable pore size and large specific surface area, which were carbonized at high temperatures and supported with Pt as catalysts for hydrogen evolution reaction. We used ZIF‐8 as the seed to obtain the precursor Co@ZIFs, W element was introduced into Co@ZIFs by impregnation method to synthesize WC. A series of Pt/WC catalysts were prepared with WC as support. The best sample Pt/WC‐3 in 0.5 M H2SO4 with a Pt content of 8.3 wt % has a low overpotential (η10=28 mV), which is much less than the 34 mV of 20% commercial Pt/C and had a Tafel slope of only 18.9 mV dec−1. It is noteworthy that at 8.3% Pt/WC after 40,000 s of continuous operation at 10 mA cm−2, the overpotential of Pt/WC‐3 barely rises by 5%, which indicates its excellent durability.

Recent Progress of Non‐Noble Metallic Heterostructures for the Electrocatalytic Hydrogen Evolution

Developing energy production, storage, and conversion technologies based on sustainable or renewable energy is essential to address the energy and environmental crisis. Electrochemical water splitting is one of the most promising approaches to realize the production of green hydrogen. The design of catalytic materials with low cost, high activity, and long‐term stability and the exploration of specific reaction mechanisms are the key focus for the involved electrochemical hydrogen evolution reaction (HER). Recently, substantial efforts have been devoted to the rational design and synthesis of non‐noble metallic heterostructures with fascinating synergistic effects among different components. These heterostructured materials demonstrate comprehensive properties exceeding the estimations by the rule of mixtures and display high activity and long‐term stability in industrial conditions for HER. Herein, the reaction mechanism and key parameters for improving catalytic performance in the HER process are discussed in detail. The latest advances in heterostructures based on synthetic methods and electrocatalytic characteristics from experimental and computational perspectives are summarized according to the role of various components. Herein, insights are provided in this review into an in‐depth understanding of the heterostructures as HER electrocatalysts, and the opportunities and challenges to scale up future‐oriented developments are highlighted.