Enhanced Hydrogen Evolution Reaction Research Articles

Structure tailorable and flexible electrospun Poly(vinylidene fluoride)@WS2 membrane with enhanced hydrogen evolution reaction activity and mechanical properties

The metallic 1T phase layered WS2 was feasible to electrocatalytic hydrogen evolution reaction (HER) compared with its 2H phase. Duo to the intrinsically stabile nature of 2H phase WS2, it is challenging to construct metallic WS2 on flexible polymeric substrate. Herein, a two-step method is proposed for constructing electrospun porous poly (vinylidene fluoride) fibers embedded with metallic WS2 an electrocatalyst. The hybrid catalysts exhibit excellent HER performance, and thanks to distinguished mechanical properties, the flexible electrocatalysts maintain their initial catalytic performance after mechanical twisting. It has been demonstrated by experimentation and COMSOL multiphysics simulations that the identity of catalytic activity not only benefits by the synergistic effect of metallic WS2, but also in favor of the three-dimensional (3D) hierarchical architectures ensuring efficacious and substantial geometric interface for catalyzing the HER. These findings expedite an unique approach to create phase-controlled flexible electrode which facilitates the blueprint of clean energy generation.

Enhanced hydrogen evolution reaction performance of MoS2 by dual metal atoms doping

Molybdenum disulfide (MoS2) has been considered a promising high-efficiency, low-cost hydrogen evolution reaction (HER) catalyst in acidic and alkaline media. However, the lack of active sites in the basal plane become the most significant obstacle hindering the widespread application of MoS2. Here, we systematically studied the HER performance of MoS2 plane or edge by co-doping Co atom and other 3d transition metals (TM = Ti–Fe, Ni) by density functional theory calculation methods. Interestingly, the dual atoms doping in both the basal plane and edges of MoS2 is a feasible fabrication with small or negative formation energies. Compared with the pristine MoS2 electrocatalyst, the HER performance in these doped systems is largely enhanced in both basal plane and edges due to the effective charge regulation on the S site by dual atom doping. Remarkably, close to zero H adsorption free energy (ΔGH = −0.161–0.119 eV) is identified for the TM-Co co-doped MoS2 basal, indicating that they are potential alternate HER electrocatalysts of Pt. Our study provides a new strategy to design highly efficient non-noble metal electrocatalysts accessibility for energy-related applications.

Three-dimensional flower-like NiS2/MoS2 assembly of randomly oriented nanoplate for enhanced hydrogen evolution reaction

The continually worsening energy crisis has stimulated research into energy conversion technology to produce pure hydrogen, H2. Transition metal-based compounds have attracted great attention as electrocatalysts for hydrogen evolution reaction (HER) as alternatives to commercial, high-cost, and scarce noble metal-based catalysts. In this work, a 3D flower-like NiS2/MoS2 is synthesized with the advantages of a three-dimensional (3D) morphology and the compositing of different metal compounds, thus leading to enhanced electrocatalytic performance. The structure of 3D flower-like NiS2/MoS2 augments the specific surface areas resulting from nanoplate assemblies as well as the heterointerface ascribed to two different phases of NiS2 and MoS2. These characteristics are confirmed by electrocatalytic measurements of the lower overpotential of 165 mV at 10 mA/cm2 with high charge transfer ability, thus demonstrating the structure's potential for advanced electrocatalysts for the HER.

Snowflake-Like Cu2S/MoS2/Pt heterostructure with near infrared photothermal-enhanced electrocatalytic and photoelectrocatalytic hydrogen production

Snowflake-like Cu2S/MoS2 heterostructures with varied compositions were constructed via a two-step hydrothermal method. The 45-Cu2S/MoS2 with 45 wt% Cu2S was found as the optimum catalyst, which displayed photothermal enhanced hydrogen evolution reaction (HER) performance under near infrared (NIR) irradiation. After electrochemical deposition of a tiny amount of Pt (45-Cu2S/MoS2/Pt-100s), Schottky barrier was formed between Pt nanoparticles and MoS2 nanosheets. Using 45-Cu2S/MoS2/Pt-100s as an electrocatalyst, low overpotential of 78 mV (@10 mV cm−2) and Tafel slope of 48 mV dec−1 were achieved with the assistance of NIR irradiation. The photoelectrochemical (PEC) hydrogen production performance of 45-Cu2S/MoS2/Pt-100s was also investigated. The optimal conversion efficiency of 45-Cu2S/MoS2/Pt-100s could reach 0.78% at 0.57 V (vs. reversible hydrogen electrode (RHE)). The control of the internal geometric and electronic structure of the catalysts and the aid of photothermal effect in this work provide new ideas for designing high-efficiency hydrogen evolution catalysts.

Interfacial synergies between single-atomic Pt and CoS for enhancing hydrogen evolution reaction catalysis

Despite the significant role of single atoms during the hydrogen evolution reaction (HER), the underlying nature of the synergetic effect between substrates and single atom is still unclear. Herein, through anchoring Pt single atoms on cobalt sulfide support (Pt@CoS), the roles of Pt single atoms and the substrate for alkaline HER catalysis are unfolded. Electrochemical studies demonstrate the remarkable catalytic performance of Pt @CoS catalysts with a 45-fold increase in mass current density compared to the benchmark Pt/C at 100 mV. The DFT calculation unravels that the anchored Pt SAs on CoS enable more unhybridized dz2 orbitals of surrounding cobalt sites through the interfacial synergetic effect, which benefits the water dissociation kinetics. Likewise, the Pt sites can also act as active sites to facilitate the subsequent H2 formation, thus synergistically promoting the alkaline HER catalysis. This work highlights the importance of the synergies effect between single atoms and substrate for rational catalyst design.

Urea electrooxidation-boosted hydrogen production on nitrogen-doped porous carbon nanorod-supported nickel phosphide nanoparticles

Urea electro-oxidation reaction (UEOR)-boosted water electrolysis can supplant the kinetics-restricted oxygen evolution reaction (OER) and provide an energy-saving method of hydrogen generation. However, low UEOR activity and the poisoning issue of the catalyst limit its practical application. Herein, a simple coordination reaction is used to synthesize the dimethylglyoxime-NiⅡ complex (DMG-NiⅡ), which efficiently serves as the initial precursor to synthesize nitrogen-doped carbon nanorod-supported nickel phosphide nanoparticle (Ni2P/N-Cnanorods) nanocomposites. The density functional theory calculations and electrochemical results reveal that nitrogen doping can weaken the adsorption of hydrogen and the generated CO2, resulting in an enhancement of hydrogen evolution reaction (HER) and UEOR activity. In addition, N-doping can also promote the generation of Ni3+, which can further promote the UEOR and HER performance. Concretely, the overpotential for the HER on Ni2P/N-Cnanorods-2h nanocomposites is only 201 mV at 10 mA cm−2, and the onset potential of the UEOR on Ni2P/N-Cnanorods-2h nanocomposites is only 1.34 V. Additionally, the Ni2P/N-Cnanorods nanocomposites also show excellent long-term stability due to the introduction of nitrogen-doped carbon material. Consequently, the symmetric Ni2P/N-Cnanorods-2h||Ni2P/N-Cnanorods-2h urea electrolyzer requires 1.41 V of electrolysis voltage for urea electrolysis, which can be applied in energy-saving H2 production and environment purification.

Temperature-Induced Structure Transformation from Co0.85Se to Orthorhombic Phase CoSe2 Realizing Enhanced Hydrogen Evolution Catalysis.

Transition-metal chalcogenides (TMC) have been widely studied as active electrocatalysts toward the hydrogen evolution reaction due to their suitable d-electron configuration and relatively high electrical conductivity. Herein, we develop a feasible method to synthesize an orthorhombic phase of CoSe2 (o-CoSe2) from the regeneration of Co0.85Se, where the temperature plays a key role in controlling the structure transformation. To the best of our knowledge, this is the first report about this synthetic route for o-CoSe2. The resulting o-CoSe2 catalysts exhibit enhanced hydrogen evolution reaction performance with an overpotential of 220 mV to reach 10 mA cm–2 in 1.0 M KOH. Density functional theory calculations further reveal that the change in the Gibbs free energy of hydrogen, water adsorption energy, and the downshifted d-band center make o-CoSe2 more suitable for accelerating the HER process.

Regulating the Heterostructure of Metal/Oxide toward the Enhanced Hydrogen Evolution Reaction

Regulating the Heterostructure of Metal/Oxide toward the Enhanced Hydrogen Evolution Reaction

Fabrication of phosphorus-mediated MoS2 nanosheets on carbon cloth for enhanced hydrogen evolution reaction

Molybdenum sulfide (MoS2) as a graphene-like sheet material has attracted wide attention owing to the potential for hydrogen evolution reaction (HER). However, the large-scale application of MoS2 is still difficult due to the inherent poor conductivity and insufficient active edge sites. Herein, we develop a simple method to grow P-doped MoS2 nanosheets on carbon cloth for high efficiency HER. The 2D carbon cloth can prevent the stacking of MoS2 nanosheets and improve the conductivity with the doping of P atoms. As a result, the P–MoS2/CC-300 shows the excellent electrocatalytic activity with an overpotential of 81 mV at 10 mA cm−2 and the lower Tafel slope of 98 mV/dec. Furthermore, it also shows the good electrocatalytic durability for 15 h. This work provides an opportunity for the design of excellent and robust MoS2-based catalyst via structural engineering and doping method.

Nanoporous TiCN with High Specific Surface Area for Enhanced Hydrogen Evolution Reaction

Transition-metal nitrides have attracted significant attention because of their unique electronic and surface properties and superior chemical and mechanical stability. Although various metal nitrides nanostructures have been realized, it remains challenging to introduce porosity and the high specific surface in these nanostructures, but they are required to expand the application possibility of these materials in energy storage and conversion. Here, we report the preparation of nanoporous titanium carbonitride using a high-nitrogen-containing mesoporous carbon nitride, C3N6 (MCN-4), as a reactive template and titanium tetrachloride as the titanium source. Nitrogen adsorption and microscopic results reveal that the prepared samples are highly nanoporous in nature, and the optimized sample exhibits a specific surface area of 700 m2/g and a high specific pore volume of 1.3 cm3/g. With the slight variation of the amount of MCN-4 in the synthesis mixture, the composition and the crystal structure of the nanoporous titanium carbonitride can be finely controlled. Near-edge X-ray absorption fine structure and Raman spectroscopic analyses of these samples confirm that the titanium atoms are strongly bonded with both carbon and nitrogen. The electrochemical hydrogen evolution reaction measurements of the optimized nanoporous titanium carbonitride loaded with 5 wt % of platinum in acidic medium reveal a high electrocatalytic performance with the overpotential of 27 mV at the current density of 10 mA cm–2, which is similar to that of commercially available Pt/C which contains 20 wt % of Pt. The combination of nanoporous structure together with the highly conducting carbon matrix in these metal carbonitride samples really helps to enhance the electrocatalytic activity. This research reveals a great opportunity for the design of porous metal nitride-based nanostructures with different composition and the potential for these materials to be used in energy storage and conversion technologies.

Origin of the Enhanced Hydrogen Evolution Reaction Activity of Grain Boundaries in MoS2 Monolayers

Origin of the Enhanced Hydrogen Evolution Reaction Activity of Grain Boundaries in MoS₂ Monolayers

Deposition of Cu on Ni3S2 nanomembranes with simply spontaneous replacement reaction for enhanced hydrogen evolution reaction

The integration of metal with transition metal disulfides (TMDs) is considered as one of the promising strategies to improve the hydrogen evolution reaction (HER) performance of TMDs through modifying the electrocatalytic kinetics. However, the deposition of metal on TMDs often requires reducing agents, surfactants or extra energy consumption, which increases the synthesis complexity and application cost. Here, metallic Cu was deposited on the Ni3S2 nanomembranes in situ grown on nickel foam (Cu/Ni3S2/NF), which is achieved through a simple replacement reaction between Cu2+ and Ni at room temperature. The microstructure characterizations reveal that Cu was uniformly distributed on Ni3S2 nanomembranes in amorphism. The XPS measurements indicate that the decoration of Cu makes the enrichment and depletion of electrons in S and Ni, respectively. Electrochemical testing shows that Cu/Ni3S2/NF has superior electrocatalytic activity with low overpotential of 130 mV to deliver a current density of 10 mA cm−2 for HER in 1.0 M KOH, and a Tafel slope of 84.19 mV dec-1. Furthermore, Cu/Ni3S2/NF possesses excellent electrocatalytic stability with nearly no increase in overpotential after continuously catalyzing for 48 h at a current density of −50 mA cm−2. This work paves the ways to prepare high-performance electrocatalysts based on metal modified TMDs with a simple and low-cost route, which is expected to promote the practical HER application of TMDs.

A simple method for synthesizing Co, P-codoped MoS2 nanoflowers as electrocatalysts to enhance hydrogen evolution reaction

A simple method for synthesizing Co, P-codoped MoS2 nanoflowers as electrocatalysts to enhance hydrogen evolution reaction

Electrochemically Reconstructed Cu‐FeOOH/Fe3O4 Catalyst for Efficient Hydrogen Evolution in Alkaline Media

AbstractSurface self‐reconstruction via incorporating an amorphous structure on the surface of a catalyst can induce abundant defects and unsaturated sites for enhanced hydrogen evolution reaction (HER) activity. Herein, an electrochemical activation method is proposed to reconstruct the surface of a Cu‐Fe3O4 catalyst. Following a “dissolution–redeposition” path, the defective FeOOH is formed under potential stimulation on the surface of the Cu‐Fe3O4 precursor during the electrochemical activation process. This Cu‐FeOOH/Fe3O4 catalyst exhibits excellent stability as well as extremely low overpotential toward the alkaline HER (e.g., 129 and 285 mV at the large current densities of −100 and 500 mA cm−2, respectively), much superior to the Pt/C catalyst. The experimental and density functional theory calculation results demonstrate that the Cu‐FeOOH/Fe3O4 catalyst has abundant oxygen vacancies, featuring optimized surface chemical composition and electronic structure for improving the active sites and intrinsic activity. Introducing defective FeOOH on the surface of a Cu‐Fe3O4 catalyst by means of an electrochemical activation method decreases the energy barrier of both H2O dissociation and H2 generation. Such a surface self‐reconstruction strategy provides a new avenue toward the production of efficient non‐noble metal catalysts for the HER.

Z-scheme MoO3-2D SnS nanosheets heterojunction assisted g-C3N4 composite for enhanced photocatalytic hydrogen evolutions

In this work, the 2D SnS/g-C3N4 nanosheets have been successfully prepared by a facile ultrasonic and microwave heating approach, which formed intimate interfacial contact and suitable energy band structure. The optimized sample displayed enhanced photocatalytic hydrogen evolution from water assisted with Pt co-catalyst, which is much higher than that of pure g-C3N4. After loaded with MoO3 particles, the stability of photocatalysts displayed significate improvement due to the formed Z-scheme heterojunction. With the characterization, the enhanced hydrogen evolution reaction (HER) performance might be ascribed to the improved light-harvesting capability of the composite, lowered charge-transfer resistance, increased electrical conductivity and the co-catalyst effect of SnS. This study provides insights about SnS assisted HER photocatalysts and a new strategy to improve the stability of metal sulfides photocatalysts.

Tuning the Electronic Structure of Tungsten Oxide for Enhanced Hydrogen Evolution Reaction in Alkaline Electrolyte

AbstractEngineering the electronic structure of HER catalysts has been suggested to improve the performance of noble metal‐free catalysts in alkaline electrolytes. Herein, we demonstrated that a suitable cation doping in the tungsten oxide catalyst modified the interfacial structure, surface chemical state and band gap value, which enhanced the HER performance. For the experiments, the cation (Ni, Co and Fe) doped tungsten oxide catalysts were synthesized on nickel foam, on which Ni‐based alloy was decorated. The Co doped catalyst (Co−WO) exhibited an extraordinary HER activity, with a low overpotential of 30 mV at a current density of 10 mA cm−2, Tafel slope of 32 mV dec−1. In this system, the Ni‐based alloy–tungsten oxide interface facilitated water dissociation. Moreover, the decreased band gap and improved conductivity induced by Co doping, further enhanced the charge transfer ability in the HER process. The regulated metal‐oxide heterostructure coupled with cation doping endowed the catalyst with efficient interface active sites, superior electrical conductivity, and enhanced electron transfer kinetics, facilitating the HER performance.

Micro Eddy Current Facilitated by Screwed MoS2 Structure for Enhanced Hydrogen Evolution Reaction

AbstractEddy current is a magnetic field effect generated in alternating magnetic field (AMF), which could trigger continuous local heating, reducing the energy consumption without impairing the life of the catalyst or reactor. Unfortunately, the investigation of eddy current effect on transition metal disulfides (TMDs) electrocatalysis is still in its infancy, and its actual electrocatalytic applications has been impeded by the multilayered structure of traditional layered TMDs. Typically, the step pyramid MoS2, with a layer‐by‐layer stacking structure just like the silicon steel plate in the transformer, showing an inevitable interlayer potential barrier will suppress the generation of eddy current and cause low efficiency of magnetic heating. In this work, the designed screw pyramid MoS2 can facilitate the formation of micro eddy current and maximize utilization of magnetic heating to boost electrocatalytic activity, benefiting from its eliminated interlayer potential barrier. This work provides a new thinking for the design of field‐assisted electrocatalytic reactions and development of the advanced catalyst technology.

Two-dimensional vanadium sulfide flexible graphite/polymer films for near-infrared photoelectrocatalysis and electrochemical energy storage

Modern wearable electronics require scalable, flexible, and conductive electrodes with tunable properties. Abundant materials such as graphite as a conductive component and polymer as a flexible component forming a composite film (electrode) via simple synthesis technique are particularly captivating. This approach conveniently satisfies the fundamental needs of an ideal electrode yet provides a conductive platform to accommodate a secondary material for various purposes in electrochemical energy conversion and storage. Accordingly, we optimize a graphite-polymer composite film with good conductivity and flexibility to incorporate two-dimensional (2D) VSx (mixed phase predominated by V5S8) as an active material within the film. We exemplify the dual functionalities of the VSx/graphite flexible electrode as i) a photo-electrocatalyst for enhanced hydrogen evolution reaction by visible and near-infrared light irradiation (overpotential ≈500 mV at the current density of −10 mA cm−2), and ii) a conductive electrode for symmetrical solid-state supercapacitor with pseudocapacitive charge storage mechanism (areal capacitance of 123 mF cm−2 and areal capacity of 34 µAh cm−2 at the current density of 0.5 mA cm−2). Our work demonstrates the versatility of graphite films in terms of size, shape, flexibility, and scalability, with tunable physical, optical, and electrical properties by integrating other secondary materials. We combine flexible graphite film and 2D vanadium sulfide with near-infrared photoresponse and pseudocapacitive properties, as an economically feasible avenue for energy harvesting, outer space application, and wearable devices.

Edge terminated and interlayer expanded pristine MoS2 nanostructures with 1T on 2H phase, for enhanced hydrogen evolution reaction

Pristine molybdenum disulfide (MoS 2 ) nanostructures with 1T on 2H phase have been prepared by tuning the growth time in hydrothermal synthesis. The optimized sample has an expanded interlayer and it exhibits striking kinetic metrics with an onset potential of - 0.13 V, Tafel slope of 49 mV/decade, and an exchange current density of 3.98 × 10 −3 mA, performing best among the pristine MoS 2 based hydrogen evolution reaction (HER) catalysts reported so far. The edge terminated structure, together with the expanded interlayer, is believed to modify the electronic structure to enhance the conductivity of the compound. The Mott-Schottky analysis of the optimized sample indicated a decrease in band bending and an enhancement in the charge transfer. The promising HER response obtained with sufficiently low growth time and growth temperature for the pristine MoS 2 nanostructures suggests a potential way to design high-performance HER catalysts based on the compound. • Fabricated edge terminated, interlayer expanded 1T on 2H MoS 2 nanostructures. • 1T phase with HER active (001) plane obtained without the addition of any dopant. • Optimized sample has lower onset potential of −0.13 V and Tafel slope of 49 mV/dec. • High exchange current density of 3.98 × 10 −3 mA for the optimized sample. • Durable HER catalyst with high stability using MoS 2 nanostructures.

A novel Ni–La-Nd-Y flim on Ni foam to enhance hydrogen evolution reaction in alkaline media

The exploration of non-precious metal catalysts has always been a hot topic. Here, a new type of Ni–La-Nd-Y film was electrodeposited on nickel foam (NF). The Ni–La-Nd-Y film shows outstanding HER activity and stability under alkaline conditions. La2NiO4 makes the electrode surface present a regular layered structure, which greatly increases the number of electrochemically active sites. Ni–La-Nd-Y only needs 46 mV overpotential driving current density of 10 mA cm−2 in 1MKOH solution, which is very close to the HER performance of metal Pt. By doping rare earth elements and taking advantage of the shrinkage characteristics of lanthanides, this work took advantage of the shrinkage characteristics of the lanthanide series and found new ideas for improving catalysts through the combination of different rare earth elements.