Electrocatalytic Hydrogen Research Articles

The CoNi@C/Mo1.33C i-MXene Derived from Novel (Mo2/3R1/3)2GaC (R = Dy, Ho, Er, Tm, and Lu) Nanolaminations for Electrochemical Application in Electrocatalytic Hydrogen Evolution and Supercapacitance.

2D Mo1.33C i-MXene is highly promising for electrochemical applications. Here, a synthetic strategy is reported, enabling the uniform distribution of carbon-coated CoNi (CoNi@C) nanoparticles on the vacancy-ordered Mo1.33C i-MXene nanosheets, thereby fully exposing the active sites of CoNi@C. First, five novel Ga-containing (Mo2/3R1/3)2GaC (R = Dy, Ho, Er, Tm, and Lu) i-MAX phases are synthesized as the precursor and found to be crystallized into Cmcm structure, followed by hydrothermal etching and delamination. Subsequently, CoNi- MOF is in situ grown on derived Mo1.33C i-MXene nanosheets. By modifying the loading mass and annealing condition, CoNi-MOF is transformed into the CoNi@C and the CoNi@C/Mo1.33C displayed outstanding hydrogen evolution reaction activity with low overpotential (73mV at 10 mA cm-2) and small Tafel slope (84 mV dec-1). Moreover, the gravimetric capacitance is also increased from 68 F g-1 in CoNi@C to 575.1 F g-1 in CoNi@C/Mo1.33C-50 at 0.5 A g-1. After ≈5000 cycles, activation is complete, and the specific capacitance reaches its maximum value. Additionally, the specific capacitance remains stable at 95% after additional 10000 cycles. This work improves the catalytic and supercapacitor performance of composite nanomaterials by optimizing the distribution of active sites on Mo1.33C i-MXene, and also extends the application of Mo1.33C i-MXene.

Lanthanide Hydroxide as a New Platform for Efficient Electrocatalytic Alkaline Hydrogen Evolution

Lanthanide Hydroxide as a New Platform for Efficient Electrocatalytic Alkaline Hydrogen Evolution

Engineering of HO–Zn–N2 Active Sites in Zeolitic Imidazolate Frameworks for Enhanced (Photo)Electrocatalytic Hydrogen Evolution

Currently, lack of ways to engineer specific and well‐defined active sites in zeolitic imidazolate frameworks (ZIFs) limits our fundamental knowledge with respect to the mechanistic details for (photo)electrocatalytic hydrogen evolution reaction (HER). Here, we introduce the open metal sites into ZIFs through the selective ligand removal (SeLiRe) strategy, comprehensively characterize the altered structural and electronic features, and evaluate their role in HER. In‐situ electrochemical analysis and X‐ray absorption spectroscopy reveal the formation of high‐valence HO−Zn−N2 sites through the binding of Zn−N2 with electrolyte hydroxide. The optimal OMS‐ZIF exhibits a low overpotential of 0.41 V to achieve an ampere‐level 1.0 A cm−2 with 120‐hour stability. Theoretical simulations indicate that these active sites accelerate the water molecules activation kinetics, consequently enhancing the efficiency of the Volmer step. This work demonstrates a versatile strategy to introduce highly active catalytic sites in ZIFs, providing new insights into the electrocatalytic mechanism in alkaline media.

Surface Nanosteps Modulate the Local Environment of Co Single Atoms to Boost the Electrocatalytic Hydrogen Evolution Reaction

Surface Nanosteps Modulate the Local Environment of Co Single Atoms to Boost the Electrocatalytic Hydrogen Evolution Reaction

Self-Supported Porous Carbon Monoliths for Electrocatalytic Hydrogen Evolution in Alkaline Freshwater and Seawater.

Developing efficient catalysts for seawater electrolysis hydrogen evolution reaction (HER) is crucial for producing green hydrogen. Carbonized wood (CW), a porous carbon monolith, is a promising self-supporting electrocatalytic electrode owing to its environmentally friendly, sustainable, and hierarchically porous properties. However, the impact of different tree species on the hydrogen evolution performance remains unclear. In this study, various types of CWs, including carbonized poplar (PoCW), carbonized balsa (BaCW), carbonized fir (FiCW), and carbonized pine (PiCW), have been selected to investigate their electrocatalytic performance in hydrogen evolution. Among these, the PoCW exhibits superior electrocatalytic HER performance compared to the other CWs, attributed to its electrochemically active surface area, resistance, and the content of oxygen-containing functional groups. PoCW demonstrates a low overpotential of 284 mV and 356 mV at 10 mA cm-2 in alkaline freshwater and seawater, respectively. Moreover, PoCW shows long-term durability for 100 h in both alkaline freshwater and seawater. This work guides the selection of wood-based carbon monoliths and demonstrates that metal-free, CW-based self-supporting electrodes hold great potential for electrocatalytic hydrogen evolution in both freshwater and seawater.

In a search of the single-atom electrocatalysts for hydrogen production: the first sulfur-free mono- and diphenanthrenyl-terminated iron and cobalt(II) clathrochelates versus their thioanalogs

This paper reports on green chemistry approaches to the molecular design and synthesis of cheap, efficient and eco-friendly electrocatalysts of the hydrogen evolution reaction (HER). The title clathrochelates (including first those do not containing sulfur derivatives as “catalytic poisons”) were prepared using nucleophilic substitution of their chloroclathrochelate precursors and characterized by analytical, spectral and XRD methods. These complexes showed the HER 2H+/H2 electrocatalytic activity in the solutions. They form the Langmuir monolayers and possess a high physisorption on activated carbon (AC, up to 0.55mmol·g–1) and reduced graphene oxide (RGO, up to 0.33mmol·g–1). Contrary that on carbon paper (CP) is very low. Therefore, AC- or RGO-containing clathrochelate-immobilized components are suitable for preparation of hybrid CP-based cathodes, allowing to substantially increase a surface concentration of electrocatalytically active centers up to 0.5 μmol·m–2. Cyclic voltammetry data suggest that the electrochemically generated cobalt(I) complexes, as the catalytically active intermediates, are stable and most prospective candidates for electrocatalytic hydrogen production. Clathrochelate-based single-atom catalysts were prepared in accordance with basic principles of green chemistry. They are derivatives of abundant and cheap 3d-biometals and low-toxic α-dioximes and possess an extremely high atomic utilization efficiency matching the “economy of atoms” principle. Nowadays, the carbon-supported metallic platinum is used as HER catalyst. The reserves of this noble and expensive metal on the Earth are limited and its replacement by such cheap and abundant HER materials will accelerate the development and implementation of green hydrogen-producing technologies. The recommendations on chemical structures of optimal molecular electrocatalysts were evaluated.

Design and construction of robust nickel-based MOFs for promoting HER catalytic activity

The proposal of the dual-carbon target has attracted widespread attention to explore hydrogen evolution reaction (HER) electrocatalysts to promote the development of clean energy. Here, we propose a strategy to form hierarchically porous electrocatalytic hydrogen evolution catalysts (MOFs I−II) by calcining prefabricated Ni-metal–organic frameworks (MOFs 1 − 2) under N2 atmosphere. Among them, three-dimensional (3D) porous MOFs 1 − 2 have been synthesized by solvothermal method based on scissor-shaped tetracarboxylic acid, named {[Ni2(L)(1,3-bit)(H2O)3](C2H3N)}n (MOF 1) and [Ni4(tib)(L)2(H2O)3(μ2-O)]n (MOF 2). Single crystal diffraction analysis shows that MOF 1 is 3,4,7-connected 3-nodes 3D framework composed of two kinds 2D planes, while MOF 2 is 2,4,7-connected 3-nodes 3D supramolecular structure constructed from 1D chains and 2D planes. As expected, SEM and BET analysis show that calcination produced a unique hierarchical micro-mesoporous structure, while the specific surface area increases by 2.3–3.8 times. The optimized MOF II exposes more active sites, accelerates electrolyte ion diffusion, and has lower electron transfer resistance, allowing it to exhibit excellent electrocatalytic HER performance in an alkaline environment. Notably, MOF II has a Tafel slope of 81 mV·dec−1 (10 mA·cm−2) with a lower overpotential (225 mV). Compared with the pristine MOF 2, the performance of MOF II is significantly improved and it can operate stably for a long time. The possible electrocatalytic HER mechanism has been investigated by density functional theory (DFT). The results are expected to provide inspiration for the rational design and development of stable and efficient MOF-based HER electrocatalysts.

Manipulation of the Electronic Structure of Ruthenium Nanoclusters by Ni‐N4 Sites Enhances the Alkaline Hydrogen Evolution Reaction

AbstractDesigning electrocatalysts that are both highly efficient and durable is crucial for the industrial implementation of alkaline electrocatalytic hydrogen production technologies. A limitation of the current Ru‐based catalysts is that the water dissociation energy barrier tends to be too high. Here, the electronic structure of ruthenium nanoclusters (Ru NCs) is modulated by single atom Ni‐N4 sites leading to leading to lowering of the water dissociation barrier. X‐ray absorption fine structure spectrum confirms that Ru NCs are stably anchored on the carbon support through the formation of Ru‐N bonds, significantly enhancing catalytic stability. The resulting Ru/Ni‐N4C‐300 catalyst shows excellent catalytic activity toward alkaline hydrogen evolution reaction with a low overpotential of 15.0 mV at 10 mA cm−2 together with robust durability. An anion exchange membrane water electrolyzer employing Ru/Ni‐N4C‐300 can be stably operated under 500 mA cm−2 for over 1370 h, surpassing the parameters required for industrialization. Theoretical calculation indicates the single atom Ni‐N4 sites in Ru/Ni‐N4C‐300 optimize the electron distribution of Ru NCs, thereby reducing the Gibbs free energy of intermediates species in water dissociation process.

Cu-induced interface engineering of NiCu/Ni3N heterostructures for enhanced alkaline hydrogen oxidation reaction

Constructing well-defined interfaces in catalysts is a highly effective method to accelerate reactions with multiple intermediates. In this study, we developed a heterostructure catalyst combining fcc NiCu and hcp Ni3N, aiming at achieving superior performance in alkaline hydrogen electrocatalysis. The NiCu/Ni3N not only overcomes the inadequate hydroxyl binding energy performance of NiCu alloys but also solves the problems of insufficient active sites found in most Ni/Ni3N. Experimental results and density functional theoretical calculations reveal that the formation of heterostructure significantly depends on the amount of Cu. This approach effectively prevents the side effects of increased catalyst particle size, typically resulting from the high temperatures and prolonged reaction times required for conventional synthesis of Ni/Ni3N. The interface of this heterostructure induces a distinctive overlapping effect that enhances the adsorption of water and lowers the energy barrier for the rate-determining step. The NiCu/Ni3N catalyst shows an impressive activity of 71.8 mA mg−1 at an overpotential of 50 mV, a 14.7 times efficiency enhancement compared to pure Ni and comparable to that of low-loaded commercial Pt/C. This research highlights the potential of NiCu/Ni3N in advancing catalyst development.

Highly porous NiCo2O4 nanostructures for enhanced electrocatalytic oxygen and hydrogen evolution reactions

Highly porous NiCo2O4 nanostructures for enhanced electrocatalytic oxygen and hydrogen evolution reactions

Oxidation of Ni(H2O)6@MoO3 to Ni2O3/MoO3 Composites by Aerial Annealing: Electrocatalytic Hydrogen Evolution.

Molybdenum trioxide (α-MoO3) is a promising and inexpensive alternative to platinum group metals (PGMs), for electrocatalytic hydrogen evolution reaction (HER). However, to make it a viable candidate for electrocatalytic systems, we must address the hurdles associated with its inferior electrical conductivity and lack of active sites. Unlike Mo-based compounds such as MoS2 and MoSe2, which possess catalytically active edges, α-MoO3 lacks inherent active sites for HER. Previous studies have employed various strategies to activate MoO3 for HER, yet its activation in near-neutral conditions remain largely unexplored. In this study, a previously known α-MoO3 intercalating {Ni(H2O)6}2+, [MoVI2O6(CH3COO){NiII(H2O)6}0.5]·H2O (Ni(H2O)6@MoO3) is prepared via a simple and scalable room-temperature aqueous synthesis. In the subsequent aerial thermal annealing process at 300, 400 and 500 °C, Ni(H2O)6@MoO3 acts as a self-sacrificial template, yielding mixed metal oxide composites of nickel and molybdenum (named as MoO3-300, MoO3-400 and MoO3-500). The HR-TEM and XPS analyses confirm the formation of the Ni2O3 phase alongside the orthorhombic α-MoO3. The annealing temperature plays a key role in the crystallinity, phase, morphology, and electrocatalytic performance of the resulting composites. The composite formed at 400 °C (MoO3-400) shows the best electrocatalytic performance among them.

NdCoO3 nanoparticles grown on reduced graphene oxide sheets as an efficient electrocatalyst for hydrogen evolution reaction

To meet the huge energy crisis due to the limitation of fossil fuel, hydrogen has been considered the most promising clean energy source due to its high efficiency, non-toxic, and clean emission products. Therefore, over the past few years, researchers have been trying to find an effective route for bulk production of hydrogen energy from water splitting. Many efforts have already been made to use suitable electrocatalysts such as transition metal-based oxides, hydroxide alloys, and carbides for hydrogen production from water splitting but these electrocatalysts are hindered due to instability over prolonged usages in alkaline solution. To overcome this issue, rare-earth perovskite oxide materials are being focussed as an efficient electrocatalyst for electrocatalytic hydrogen evolution reaction (HER) through water splitting in an alkaline medium. In the present work, we have explored to synthesize the rare-earth perovskite neodymium cobalt oxide (NdCoO3) nanoparticles grown on reduced graphene oxide (rGO) sheet, via a hydrothermal route for electrochemical hydrogen evolution in an alkaline medium. The NdCoO3/rGO nanocomposite shows a remarkably low overpotential of 84mV at the desired current density of 10 mA/cm2, compared to pristine NdCoO3 and rGO. The synergistic impact between NdCoO3 and the rGO backbone, resulting in enhanced efficiency in the HER. The nanocomposite also shows high stability and durability even more than 100 h of electrolysis under an inert atmosphere.

Design Principle and Regulation Strategy of Noble Metal‐Based Materials for Practical Proton Exchange Membrane Water Electrolyzer

AbstractGreen hydrogen holds immense promise in combating climate change and building a sustainable future. Owing to its high power‐to‐gas conversion efficiency, compact structure, and fast response, the proton exchange membrane water electrolyzer (PEMWE) stands out as the most viable option for the widespread production of green hydrogen. However, the harsh operating conditions of PEMWE make it heavily dependent on noble metal‐based catalysts (NMCs) and incur high operational and maintenance costs, which hinder its extensive adoption. Hence, it is imperative to improve the performance and lifespan of NMCs and develop advanced components to reduce the overall costs of integrating PEMWE technology into practical applications. In light of this, the fundamental design principles of NMCs employed in acidic water electrolysis are summarized, as well as recent advancements in compositional and structural engineering to enhance intrinsic activity and active site density. Moreover, recent innovations in stack components of practical PEMWE and their impact on cost‐benefit and lifespan are presented. Finally, the current challenges are examined, and potential solutions for optimizing NMCs and PEMWE in electrocatalytic hydrogen production are discussed.

Operando elucidation of hydrogen production mechanisms on sub-nanometric high-entropy metallenes

Precise morphological control and identification of structure-property relationships pose formidable challenges for high-entropy alloys, severely limiting their rational design and application in multistep and tandem reactions. Herein, we report the synthesis of sub-nanometric high-entropy metallenes with up to eight metallic elements via a one-pot wet-chemical approach. The PdRhMoFeMn high-entropy metallenes exhibit high electrocatalytic hydrogen evolution performances with 6, 23, and 26 mV overpotentials at −10 mA cm−2 in acidic, neutral, and alkaline media, respectively, and high stability. The electrochemical measurements, theoretical simulations, and operando X-ray absorption spectroscopy reveal the actual active sites along with their dynamics and synergistic mechanisms in various electrolytes. Specially, Mn sites have strong binding affinity to hydroxyl groups, which enhances the water dissociation process at Pd sites with low energy barrier while Rh sites with optimal hydrogen adsorption free energy accelerate hydride coupling, thereby markedly boosting its intrinsic ability for hydrogen production.

Hydrogen evolution performance of single atom catalyst supported on holey graphdiyne

Abstract Electrocatalytic hydrogen production is an effective method to solve environmental issues and energy crisis. However, cheap and high performance electrocatalysts are still very scarce. In this work, the hydrogen evolution reaction performance of holey graphdiyne supported transition metals single-atom catalysts (TM-SAC-HGY) were investigated by first-principles study. It is found that TM atoms are stably anchored on monolayer HGY by forming TM-C bonds. Meanwhile, TM atoms transfer electrons to both HGY and H atom. More importantly, the H adsorption free energy (ΔGH) of Cu-SAC-HGY is 0.028 eV, which is very close to 0 eV. Therefore, Cu-SAC-HGY has excellent HER activity. By analyzing the results of partial density of states, it can be concluded that the orbital hybridization strength of TM and H plays a decisive role in affecting HER activity. This work could contribute to the development of more efficient HER electrocatalysts.

Biphasic 1T/2H-MoS2 Nanosheets In Situ Vertically Anchored on Reduced Graphene Oxide via Covalent Coupling of the Mo-O-C Bond for Enhanced Electrocatalytic Hydrogen Evolution.

Transition-metal dichalcogenides (TMDs) have recently emerged as promising electrocatalysts for the hydrogen evolution reaction owing to their tunable electronic properties. However, TMDs still encounter inherent limitations, including insufficient active sites, poor conductivity, and instability; thus, their performance breakthrough mainly depends on structural optimization in hybridization with a conductive matrix and phase modulation. Herein, a 1T/2H-MoS2/rGO hybrid was rationally fabricated, which is characterized by biphasic 1T/2H-MoS2 nanosheets in situ vertically anchored on reduced graphene oxide (rGO) with strong C-O-Mo covalent coupling. The rGO substrate improves the conductivity and ensures high-dispersed 1T/2H-MoS2 nanosheets to expose plentiful highly active edges. More importantly, the strong heterointerface electrical interaction by the C-O-Mo covalent bond can enhance the charge-transfer efficiency and reinforce structural stability. Furthermore, the integration with the appropriate 2H phase is in favor of stabilization of the metastable 1T phase; thus, the ratio of 1T and 2H was precisely regulated to balance activity and stability. With these advantages, the 1T/2H-MoS2/rGO catalyst presents a satisfactory activity and stability, as confirmed by the relatively low overpotential (268 and 140 mV at 10 mA cm-2) and the small Tafel slope (102 and 86 mV dec-1) in alkaline and acidic media, respectively. The theory calculations disclose that the electronic structure redistribution has been optimized via the strong coupled C-O-Mo heterointerface and phase interface, significantly reducing the adsorption free energy of hydrogen and improving intrinsic activity.

Microwave Shock Synthesis of Porous 2D Non‐Layered Transition Metal Carbides for Efficient Hydrogen Evolution

ABSTRACTTransition metal carbides (TMCs) serve as efficient catalysts for electrocatalytic hydrogen evolution reactions (HERs), holding significant importance in promoting hydrogen production for carbon neutrality. To optimize interfacial catalytic activity, structurally designing TMCs into two‐dimensional (2D) and porous structures to expose more practical surface areas and enhance electronic configurations is a common and effective strategy. Particularly, porous 2D non‐layered TMCs (2D NL‐TMCs) demonstrate richer active sites distinct from layered interfacial inertness. However, mainstream selective etching and chemical deposition growth mechanisms struggle to prepare highly active porous 2D NL‐TMCs due to constraints posed by their high structural strength and formation temperature. Herein, we successfully synthesized porous 2D W2C (2D p‐W2C) rapidly using a microwave shock method. Mechanistic verification reveals that leveraging transient high temperature and rapid on‐off properties of microwave effectively combines with an oxidation‐induced porosity mechanism, facilitating the evolution of porous 2D structures. These low‐dimensional nanostructures with abundant edge defect sites aid in efficient adsorption reactions of intermediate species in HER. Moreover, the successful preparation of a series of porous 2D NL‐TMCs (Mo2C, NbC, TaC) confirms the universality of this method, with the synthesized 2D p‐W2C exhibiting optimal HER performance. This strategy offers new insights into the topological synthesis of porous 2D NL crystals.

High stability of electrocatalytic hydrogen evolution from Ru-WC/NC 0D-2D nanocomposites

Pt based noble metal catalysts are important and efficient electrocatalysts during hydrogen evolution reaction (HER). However, the HER of Pt based noble metal catalysts have poor stability and high cost. Herein, Unique Ru loaded the tungsten carbide/nitrogen doped carbon (Ru-WC/NC) 0D-2D nanocomposites were fabricated by gas-phase reduction pyrolysis process to solve the problem of poor stability and high cost. Specifically, 0D WC-supported ultra-small Ru (∼2 nm) was anchored on nitrogen doped carbon nanosheets. Even with a remarkably low Ru loading of just 2.82 %, the developed catalyst achieves comparable high catalytic performance to that of a 20 % Pt/C catalyst and demonstrates superior stability. Under a current density of 10 mA cm−2, the Ru(2)-WC/NC catalyst shows an overpotential of 30 mV in acidic conditions and 51 mV in alkaline environments. Additionally, the overpotential of Ru(2)-WC/NC lower than that of commercially 20 % Pt/C at high current densities exceeding 50 mA cm−2. The total potential of water splitting for the two-electrode system comprising Ru(2)-WC/NC with commercial ruthenium oxide was 1.56 V at 10mA cm−2. Most importantly, the stability of Ru(2)-WC/NC is much better than that of Pt/C. Theoretical calculation results further revealed that the ΔGH* of Ru(2)-WC/NC catalyst could be reduced through synergistic interactions between Ru and WC, thereby optimizing the kinetics of HER. This study offers both theoretical insights and practical methodologies for the synthesis and evaluation of electrocatalysts modified with low loading of noble metals.

Neutral nickel complexes with tetradentate N-heterocyclic carbene amidate ligands for electrocatalytic hydrogen evolution.

Neutral nickel complexes bearing tetradentate N-heterocyclic carbene (NHC) amidate ligands were prepared; the effect of the electronic properties of the ligand on the redox behavior as well as the electrocatalytic activity for hydrogen evolution reaction (HER) were investigated.

Coordination Induced Spin State Transition Switches the Reactivity of Nickel (II) Porphyrin in Hydrogen Evolution Reaction

Electron spin plays a critical role in chemical processes, particularly in reactions involving metal complexes with unpaired electrons. However, more definitive state‐to‐state experiments are needed to better elucidate the role of electronic spin. Herein, we chose nickel (II) 5,10,15,20‐tetrakis(pentafluorophenyl) porphyrin 1 as a catalyst, which allows switching from a low spin to a high spin state of Ni(II) center through an axial pyridine coordination, for electrocatalytic hydrogen evolution reaction (HER). When pyridine is present, we observed β‐hydrogenation of porphyrin through electron transfer followed by proton transfer. In contrast, hydrogen evolution mainly occurs via the concerted proton‐coupling electron transfer without pyridine coordination. Similar distinct spin‐dependent selectivity was also observed in chemical reduction of 1 by CoCp2 with subsequent addition of pyridinium p‐toluenesulfonate. Computational calculations using density functional theory demonstrated that the transition from low spin to high spin state enriches the ligand’s electron density after one‐electron reduction, leading to preferential protonation of β‐periphery rather than meso‐position or metal center.