Electrocatalytic Hydrogen Evolution Performance Research Articles

Strain‐Modulated Hydrogen Production Performance in Monolayer MoS2 Electrocatalysis Nanodevices

AbstractThe integration of flexible micro‐ and nanodevices plays a pivotal role in investigating stress‐enhanced performances and underlying intrinsic mechanisms for two‐dimensional materials. This study presents the fabrication of single‐crystal flexible devices using monolayer MoS2 and its catalytic activities for the hydrogen evolution reaction under stress conditions. A metallic conductive layer was deposited on the photoresist surface via magnetron sputtering, overcoming the challenges associated with lithography on insulating substrates using electron beam lithography (EBL). The results demonstrate optimal etch patterns with a metal modification layer thickness of 10.97 nm. Leveraging this flexible device fabrication process, a single‐layer MoS2 single‐nanosheet flexible micro/nano device was developed and subsequently strain‐modulated (stretched along the zigzag lattice direction with the armchair lattice direction as the axis). A significant enhancement is observed in the electrocatalytic hydrogen evolution performance as the strain increases from 0 % to 0.40 %. Notably, the onset overpotential decreased from 155.6 to 95.7 mV, and the Tafel slope decreased from 175.3 to 98.6 mV dec−1. This study provides new insights into the design and performance of strain devices for two‐dimensional (2D) monocrystalline/polycrystalline materials.

Uniaxial Magnetization and Electrocatalytic Performance for Hydrogen Evolution on Electrodeposited Ni Nanowire Array Electrodes with Ultra-High Aspect Ratio.

Ni nanowire array electrodes with an extremely large surface area were made through an electrochemical reduction process utilizing an anodized alumina template with a pore length of 320 µm, pore diameter of 100 nm, and pore aspect ratio of 3200. The electrodeposited Ni nanowire arrays were preferentially oriented in the (111) plane regardless of the deposition potential and exhibited uniaxial magnetic anisotropy with easy magnetization in the axial direction. With respect to the magnetic properties, the squareness and coercivity of the electrodeposited Ni nanowire arrays improved up to 0.8 and 550 Oe, respectively. It was also confirmed that the magnetization reversal was suppressed by increasing the aspect ratio and the hard magnetic performance was improved. The electrocatalytic performance for hydrogen evolution on the electrodeposited Ni nanowire arrays was also investigated and the hydrogen overvoltage was reduced down to ~0.1 V, which was almost 0.2 V lower than that on the electrodeposited Ni films. Additionally, the current density for hydrogen evolution at -1.0 V and -1.5 V vs. Ag/AgCl increased up to approximately -580 A/m2 and -891 A/m2, respectively, due to the extremely large surface area of the electrodeposited Ni nanowire arrays.

Adjustable anion and cation vacancies CoSe catalysts on improving activity in photoelectrochemistry and electrocatalysis

Vacancies have a significant impact on catalysts as crystal structure, band structure and surface active sites. The effect of anion and cation vacancies on the catalytic performance of CoSe was studied. Catalysts with cation Co vacancies, anion Se vacancies and anion cation double vacancies were obtained. The results show that the single Co vacancy CovSe will form many pores as the active sites in the lattice and the position of the conduction band greatly moves from 0.55 eV of CoSe to −0.46 eV. This significantly improves the electrocatalytic hydrogen evolution performance, with overpotential of 161 mV and Tafel slope of 58 mV/dec. As a comparison, the overpotential of CoSe is 401 mV (Tafel slope of 171 mV/dec). In addition, Co vacancies can also improve carrier mobility and separation efficiency, demonstrating excellent photocurrent of 11.82 mA/cm2 at 1.23 eV (RHE), with 5.91 % conversion efficiency. The overall performance of CoSev with individual Se anion vacancies is not as good as CovSe. This indicates that cationic vacancies have a greater impact on the catalyst. There was no significant improvement in the performance of the sample with double vacancies of anions and cations, indicating that the two vacancies may have offset each other.

Fe-doped promotes phosphorization and dispersibility of Ni catalysts for efficient and stable HER and OER

Developing efficient, stable, and cost-effective catalysts is crucial for hydrogen production through electrolysis of water. In this study, a comprehensive work was conducted on the electrocatalytic hydrogen and oxygen evolution performance of nickel-based phosphides doped with metallic iron. The Ni5P4/Ni2P/Fe2P catalysts with heterostructure were synthesized via a simple two-step synthetic route: (i) NaBH4 pretreatment and in situ hydrolysis, (ii) low-temperature phosphating. It was found that iron doping not only improves the dispersibility but also increases the valence state of nickel in phosphating products. The Ni5P4/Ni2P/Fe2P-2 catalyst prepared with a molar ratio of 3 between Ni and Fe exhibits the best performance for HER and OER. In detail, only 185 and 190 mV overpotentials in acidic and alkaline electrolytes are required when the current density of hydrogen production is 10 mA cm−1, respectively. To achieve the same current density under alkaline conditions, an overpotential of 215 mV is required for oxygen evolution, which is superior to IrO2. This work would enlighten the construction of more advanced bifunctional catalysts (HER and OER) via metal Fe doping.

Recent Advances in Doping Strategies to Improve Electrocatalytic Hydrogen Evolution Performance of Molybdenum Disulfide

Recent Advances in Doping Strategies to Improve Electrocatalytic Hydrogen Evolution Performance of Molybdenum Disulfide

Cu/Fe-MOFs based on mixed ligands: Synthesis, crystal structure and electrocatalytic hydrogen evolution performance

Two new metal-organic framework complexes Cu-MOF (C28H16Cu2N6O9S2) and Fe-MOF (C28H17FeN6O9S2) were synthesized with 4-[5-(pyridin-4-yl)-[1,3]thiazolo[5,4-d] [1,3]thiazol-2-yl]pyridine (Py2TTz) and pyridine-2,6-dicarboxylic acid (DPA) as mixed ligands. The single crystal X-ray diffraction results displayed that Cu2+ coordinated with Py2TTz and DPA to form 3D network structure while Fe2+ coordinated only with DPA to form 2D laminar structure, in which Py2TTz interspersed between bilayer iron complexes. The presence of Py2TTz enlarged the pore size of Fe-MOF, increasing its Brunauer-Emmett-Teller (BET) surface area and specific surface area, while the 3D structure of Cu-MOF facilitated electron transport and mass transfer. As a result, the hydrogen evolution reaction (HER) performance of Cu-MOF was slightly higher than that of Fe-MOF. This work provided an interesting idea for the design and synthesis of inexpensive HER electrocatalysts.

Hydrogen Spillover Phenomenon at the Interface of Metal-Supported Electrocatalysts for Hydrogen Evolution.

ConspectusHydrogen spillover, as a well-known phenomenon for thermal hydrogenation, generally involves the migration of active hydrogen on the surface of metal-supported catalysts. For thermocatalytic hydrogenation, hydrogen spillover generally takes place from metals with superiority for dissociating hydrogen molecules to supports with strong hydrogen adsorption under a H2 environment with high pressures. The former can bring high hydrogen chemical potential to largely reduce the kinetic barrier of the migration of active hydrogen species from metals to supports. At the same time, the latter can make H* migration thermodynamically spontaneous. For these reasons, hydrogen spillover is a common interfacial phenomenon occurring on metal-supported catalysts during thermocatalysis. Recently, this phenomenon has been observed for the exceptionally enhanced electrocatalytic performance for hydrogen evolution and other electrocatalytic organic synthesis. Different from hydrogen spillover for thermocatalysis under high H2 pressure, hydrogen spillover for electrocatalysis involves the migration of active hydrogen species (H*) from metals with strong hydrogen adsorption to supports with weak hydrogen adsorption, thereby suffering from a thermodynamically unfavorable process accompanied by a high kinetic barrier. Thus, the occurrence of hydrogen spillover at the electrocatalytic interface is not easy, and successful cases are rare. Understanding the underlying nature of hydrogen spillover at the electrocatalytic interface of metal-supported catalysts is critical to the rational design of advanced electrocatalysts.In this Account, we provide in-depth insights into recent advances in hydrogen spillover at the electrocatalytic interface for a significantly enhanced hydrogen evolution performance. Electron accumulation at the metal-support interface induces severe interfacial H* trapping and is recognized as the main factor in the failed hydrogen spillover. Given this, we developed two novel strategies to promote the occurrence of hydrogen spillover at the electrocatalytic interface. These strategies include (i) the introduction of ligand environments to enrich the local hydrogen coverage on metals and lower the barrier for interfacial hydrogen spillover and (ii) the minimization of work function difference between metals and supports (ΔΦ) to relieve electron accumulation and lower the kinetic barrier for hydrogen spillover. Also, we summarize the previously reported strategy of shortening the metal-support interface distance to lower the kinetic barrier for interfacial hydrogen spillover. Afterward, some criteria and methodologies are proposed to identify the hydrogen spillover phenomenon at the electrocatalytic interface. Finally, the remaining challenges and future perspectives are also discussed. Based on this Account, we aim to provide new insights into electrocatalysis, particularly the targeted control of hydrogen spillover at the electrocatalytic interface, and then to offer guidelines for the rational design of advanced electrocatalysts.

Bi2O3@MoS2 heterojunction for enhanced photoelectrocatalytic hydrogen evolution

A Z-type Bi2O3@MoS2 heterojunction was successfully synthesized using a hydrothermal method. Bi2O3 microflowers served as a growth support for MoS2. The Bi2O3@MoS2-10 heterojunction demonstrated optimal photoelectrocatalytic performance as a result of adjusting the loading of MoS2. It exhibited excellent electrocatalytic hydrogen evolution performance, with an overpotential of only 223 mV vs. RHE. This value is approximately half that of pure MoS2 and one-third of Bi2O3. Under illumination, the overpotential for the hydrogen evolution reaction of the Bi2O3@MoS2-10 heterojunction decreased by ∼ 35 mV when the current density reached −10 mA cm−2, compared to dark conditions. The improved performance can be attributed to the growth of MoS2 on the Bi2O3 support, which prevents the aggregation of MoS2 nanosheets and results in a layered structure with a large surface area. Furthermore, the introduction of Bi2O3 as a co-catalyst lowers the bandgap energy of the heterojunction, facilitating efficient separation and rapid transfer of photogenerated electrons and holes. As a result, this growth induces band bending near the heterojunction interface, leading to the rearrangement of energy levels and the redistribution of charges through the interaction between Bi2O3 and MoS2. Moreover, photogenerated electrons can efficiently transfer to the heterojunction surface, participating in the reduction of H+/H3O+ ions to produce H2. This enhances the photoelectrocatalytic hydrogen evolution performance of the Bi2O3@MoS2-10 heterojunction.

Preparation and Electrocatalytic Hydrogen Evolution Performance of FeCoNiCrMo High-Entropy Alloy Porous Electrode with Different Pore-Forming Agent Content

Preparation and Electrocatalytic Hydrogen Evolution Performance of FeCoNiCrMo High-Entropy Alloy Porous Electrode with Different Pore-Forming Agent Content

Ni-Co-B-RE (Sm, Dy, Tb) Composite Electrodes: Preparation by Chemical Deposition Method and Electrocatalytic Hydrogen Evolution Performance

Ni-Co-B-RE (Sm, Dy, Tb) Composite Electrodes: Preparation by Chemical Deposition Method and Electrocatalytic Hydrogen Evolution Performance

Highly Exposed MoS2 Nanosheets Grown Under pH Modulated Non-Equilibrium Hydrothermal Route and Its Electrocatalytic Hydrogen Evolution Performance

: Molybdenum disulfide (MoS2) has emerged as a highly potential noble metal-free electrocatalyst for the Hydrogen Evolution Reaction (HER). However, edge sites of MoS2 created by sulphur non-stoichiometry play a prominent role in influencing the HER activity. In this work we adopt a simple hydrothermal route under a non-equilibrium condition with in-situ pH modulation, to synthesize its highly exposed edge sites MoS2 which have not been reported so far, and study the variation of its physio-chemical properties that enable an efficient electrocatalytic activity. Electrochemical measurements and impedance studies are conducted to understand harmonic morphology, and structural and composition variation, which were responsible for the activity. Additionally, the Density Functional Theory is adopted to support the enhanced hydrogen absorption and desorption processes in synchronous with various non-stoichiometric structures.

Optimizing electrocatalytic hydrogen evolution performance of derived materials by using organic ligands containing sulfur elements for Co-MOF

The rational preparation and development of efficient and stable non-precious metal catalysts for the hydrogen evolution reaction are an effective solution to solve the global energy shortage and the increasing environmental pollution problems. Herein, two Co-MOFs with similar structures were designed and synthesized, one based on sulfur-containing organic ligand and the other based on non-sulfur-containing organic ligand. The electrocatalytic performance results showed that the materials based on sulfur-containing organic ligand had a better electrocatalytic hydrogen evolution performance. The reasons of performance differentiation were analyzed by various characterization techniques.

Synergetic Effect and Phase Engineering by Formation of Ti3C2Tx Modified 2H/1T-MoSe2 Composites for Enhanced HER

The typical semi conductivity and few active sites of hydrogen evolution of 2H MoSe2 severely restrict its electrocatalytic hydrogen evolution performance. At the same time, the 1T MoSe2 has metal conductivity and plentiful hydrogen evolution sites, making it feasible to optimize the electrocatalytic hydrogen evolution behavior of MoSe2 using phase engineering. In this study, we, through a simple one-step hydrothermal method, composed 1T/2H MoSe2, and then used newly emerging transition metal carbides with several atomic-layer thicknesses Ti3C2Tx to improve the conductivity of a MoSe2-based electrocatalyst. Finally, MoSe2@Ti3C2Tx was successfully synthesized, according to the control of the additional amount of Ti3C2Tx, to form a proper MoSe2/ Ti3C2Tx heterostructure with a better electrochemical HER performance. As obtained MoSe2@4 mg-Ti3C2Tx achieved a low overpotential, a small Tafel slope and this work offers additional insight into broadened MoSe2 and MXenes-based catalyst’s electrochemical application.

Modulating Electronic Structures of Bimetallic Co-Fe Sulfide Ultrathin Nanosheet Supported on g-C3N4 Promoting Electrocatalytic Hydrogen Evolution Performance

Heteroatom doping is a possible way to regulate the catalytic capability of electrocatalysts for hydrogen evolution reaction (HER). This work focuses on the development of bimetallic Cobalt-Iron sulfide ultrathin nanosheets supported on the graphitic carbon nitride (g-C3N4) catalyst as efficient HER electrocatalysts (CoS2/FeS2/CN) with good stability at wide pH value. The ultrathin nanosheet exposes more active sites and enhances the catalyst activity. Electrochemical experiments demonstrate that adding g-C3N4 and Fe to CoS2 increases its catalytic activity and stability. Furthermore, g-C3N4 and Fe co-doped with CoS2 can modulate electronic structures on the interface. The CoS2/FeS2/CN exhibits outstanding HER performance, reaching a current density of 10 mA cm−2 with overpotentials of only 76.5 mV in an acidic solution and 175.6 mV in an alkaline solution. It also demonstrates exceptional durability, superior to commercial platinum/carbon catalysts. This work introduces a promising approach for designing low-cost, high-performance HER electrocatalysts with a wide pH range.

Construction of interface-engineered coral-like nickel phosphide@cerium oxide hybrid nanoarrays to boost electrocatalytic hydrogen evolution performance in alkaline water/seawater electrolytes

Construction of interface-engineered coral-like nickel phosphide@cerium oxide hybrid nanoarrays to boost electrocatalytic hydrogen evolution performance in alkaline water/seawater electrolytes

Effective Hydrogen Production from Alkaline and Natural Seawater using WO3-x@CdS1-x Nanocomposite-Based Electrocatalysts.

Offshore hydrogen production through water electrolysis presents significant technical and economic challenges. Achieving an efficient hydrogen evolution reaction (HER) in alkaline and natural seawater environments remains daunting due to the sluggish kinetics of water dissociation. To address this issue, we synthesized electrocatalytic WO3-x@CdS1-x nanocomposites (WCSNCs) using ultrasonic-assisted laser irradiation. The synthesized WCSNCs with varying CdS contents were thoroughly characterized to investigate their structural, morphological, and electrochemical properties. Among the samples tested, the WCSNCs with 20 wt % CdS1-x in WO3-x (Wx@Sx-20%) exhibited superior electrocatalytic performance for hydrogen evolution in a 1 M KOH solution. Specifically, the Wx@Sx-20% catalyst demonstrated an overpotential of 0.191 V at a current density of -10 mA/cm2 and a Tafel slope of 61.9 mV/dec. The Wx@Sx-20% catalysts demonstrated outstanding stability and durability, maintaining their performance after 24 h and up to 1000 CV cycles. Notably, when subjected to natural seawater electrolysis, the Wx@Sx-20% catalysts outperformed in terms of electrocatalytic HER activity and stability. The remarkable performance enhancement of the prepared electrocatalyst can be attributed to the combined effect of sulfur vacancies in CdS1-x and oxygen vacancies in WO3-x. These vacancies promote the electrochemically active surface area, enhance the rate of charge separation and transfer, increase the number of electrocatalytic active sites, and accelerate the HER process in alkaline and natural seawater environments.

Unsaturated bi‐heterometal clusters in metal‐vacancy sites of 2D MoS2 for efficient hydrogen evolution

AbstractThe valence states and coordination structures of doped heterometal atoms in two‐dimensional (2D) nanomaterials lack predictable regulation strategies. Hence, a robust method is proposed to form unsaturated heteroatom clusters via the metal‐vacancy restraint mechanism, which can precisely regulate the bonding and valence state of heterometal atoms doped in 2D molybdenum disulfide. The unsaturated valence state of heterometal Pt and Ru cluster atoms form a spatial coordination structure with Pt–S and Ru–O–S as catalytically active sites. Among them, the strong binding energy of negatively charged suspended S and O sites for H+, as well as the weak adsorption of positively charged unsaturated heterometal atoms for H*, reduces the energy barrier of the hydrogen evolution reaction proved by theoretical calculation. Whereupon, the electrocatalytic hydrogen evolution performance is markedly improved by the ensemble effect of unsaturated heterometal atoms and highlighted with an overpotential of 84 mV and Tafel slope of 68.5 mV dec−1. In brief, this metal vacancy‐induced valence state regulation of heterometal can manipulate the coordination structure and catalytic activity of heterometal atoms doped in the 2D atomic lattice but not limited to 2D nanomaterials.

Construction of urchin-like bimetallic phosphides induced by carbon dots for efficient wide pH hydrogen production

The development of an efficient noble-metal-free and pH-universal electrocatalyst for the hydrogen evolution reaction (HER) would be highly significant for hydrogen (H2) production via electrocatalytic water splitting. However, developing such a catalyst remains a formidable task. Herein, a strategy is proposed for the in situ fabrication of a novel urchin-like NiCoP microsphere catalyst (0.5CDs-NiCoP/NF) on nickel foam (NF) using carbon dots (CDs) as a directing agent. The strong bonding between the CDs and metals provides additional active sites, giving 0.5CDs-NiCoP/NF excellent electrocatalytic hydrogen evolution performance in environments ranging from acidic to basic. Moreover, the unique structure of 0.5CDs-NiCoP/NF endows this catalyst with low Tafel slopes of 73, 146 and 74 mV dec−1 for HER in acidic, neutral and alkaline conditions, respectively. This performance exceeds that of numerous other reported non-precious HER catalysts. In summary, this work offers a novel and efficient strategy for the design and synthesis of low-cost, efficient, and robust transition metal phosphides (TMPs) electrocatalysts.

Synthesis of Fe Atom-Doped Monodisperse Co2P Nanorods with a Dual-Ligand Strategy for Excellent Electrocatalytic Hydrogen Evolution Performance.

Cobalt phosphide has been widely used in various catalytic reactions due to its excellent catalytic activity and stability. In contrast to the conventional synthesis of Co2P nanorods using expensive and toxic trioctylphosphine (TOP), this study employs a dual-ligand strategy to prepare iron-atom-doped monodisperse Co2P nanorods. The strategy involves the use of triphenylphosphite (TPOP) as a cost-effective and relatively less toxic strong ligand, alongside hexadecylamine (HDA) as a weaker ligand. The resultant atom-doped Co2P nanorods exhibited a large aspect ratio, providing a plentiful supply of active sites for electrocatalytic hydrogen evolution. In both alkaline and acidic electrolytes, achieving a current density of 10 mA cm-2 required overpotentials of 91 and 141 mV, respectively, with the optimal Co:Fe molar ratio of 1:0.2. The introduction of Fe atoms through doping increased the electron density at the Co atom sites, thereby enhancing H adsorption. This research offers a cost-effective and relatively low-toxicity method for the controlled fabrication of monodisperse transition-metal phosphide nanorods, enabling efficient catalytic reactions.

Amorphous nickel oxide electrodes with high-current-density electrocatalytic performance for hydrogen evolution

The widespread use of unsustainable fossil fuels has caused serious damage to the ecological environment. The development of sustainable clean energy is urgent. Producing hydrogen by water electrolysis can effectively solve fossil energy shortage and environmental pollution issues. The preparation of inexpensive, efficient, and stable electrocatalytic hydrogen evolution electrode materials is the key to achieving the application of electrocatalytic hydrogen evolution. Herein, the amorphous nickel oxide/nickel foam (NiOx/NF) hydrogen evolution electrode was prepared by a simple one-step hydrothermal method with hydrogen peroxide as an oxidant. The amorphous leaf array structure of NiOx/NF electrode can enrich the surface composition and expose more catalytic active sites. Further, hydrogen peroxide etching can optimize the electronic structure of NiOx, and accelerate the electron migration. Thus, NiOx/NF displays excellent alkaline hydrogen evolution activity with the low over potentials of 70, 318 and 361 mV at 10, 500 and 1000 mA cm−2, respectively, leading to high performance in alkaline HER than those of reported Ni-based electrodes and even surpasses commercial Pt/C at high current density. Our work provides a new approach for developing inexpensive electrocatalysts with excellent alkaline hydrogen evolution activity and stability.