Zinc oxide functionalized molybdenum disulfide heterostructures as efficient electrocatalysts for hydrogen evolution reaction

Technology urges to replace the state-of-the-art catalysts such as platinum with low cost, earth abundant and durable electrocatalysts for efficient hydrogen evolution (HER) reaction which is going to become the major sustainable production of energy in future. Herein, we present the heterostructure based MoS₂.ZnO (MZO) heterostructures for successful electrochemical water splitting process. For HER, the prepared MoS₂.ZnO nanocomposites show the over potential as low as 239 mV at cathodic current density 10 mAcm⁻² with an exchange current density of 3.2 μAcm⁻². A Tafel slope of about 62 mV per decade suggested to have the Volmer-Heyrovsky mechanism for the HER process with MoS₂.ZnO nanocomposite as the catalyst. The small Tafel slope indicates a promising electrocatalyst for HER in practical application. The strong interface formation at the MoS₂.ZnO heterostructure facilitates higher catalytic activity and excellent cycling stability. The heterostructure formation based on semiconductor two dimensional (2D) transition metal dichalcogenides (TMDC) open up new avenues for effective manipulation of HER catalysts.     

Exposure of active edge structure for electrochemical H2 evolution from VS2/MWCNTs hybrid catalysts

Developing highly efficient and stable non-noble-metal catalysts for electrochemical hydrogen production is the main subject toward energy conversion systems. In this work, the vanadium disulfide/multi-walled carbon nanotubes (VS₂/MWCNTs) is synthesized by a facile hydrothermal process. The introducing of MWCNTs could provide abundant sites for the anchoring of VS₂ to expose more edge structure. Besides, the electron transfer from MWCNTs to VS₂ could increase the electron density of VS₂ and further enhance the HER performance of the composites. The optimized VS₂/MWCNTs composite exhibits excellent HER properties with a small η₁₀ of 123 mV and low Tafel slope of 40 mV dec^?1. Meanwhile, the cobwebby network of the hybrid could significantly improve the electron transfer and durability of the catalyst. This work provides an available route for further application of the transition metal dichalcogenides based nanostructure.     

Porous CoP nanostructure electrocatalyst derived from DUT-58 for hydrogen evolution reaction

The development of efficient, non-precious metal catalysts for preparing hydrogen by water decomposition, which is a perfect alternative for increasingly serious environmental pollution and energy needs. In this work, we report that a porous CoP-350 nanostructure material was prepared using Co-based metal organic frameworks (DUT-58) as the precursor by pyrolysis and low temperature phosphating. The porous CoP-350 nanostructure electrocatalyst in this report exhibits excellent performance with a small Tafel slope of 64 mV dec^?1, long-term durability and an overpotential of 126 mV at current density 10 mA cm^?2 in 0.5 M H₂SO₄ for the hydrogen evolution reaction (HER). All in all, this work provides an approach to synthesize porous CoP nanostructure as the transition metal phosphides catalyst.     

MOF-derived NiSe2 nanoparticles grown on carbon fiber as a binder-free and efficient catalyst for hydrogen evolution reaction

It is challenging to grow inexpensive cathode material with superior catalytic properties for hydrogen evolution reaction (HER). Metal-organic frameworks (MOFs) have emerged as powerful platforms to synthesize efficient and ultrastable catalysts for hydrogen production. In this research, NiSe₂ nanoparticles were derived from Ni-based MOF, which grown in situ on carbon fiber (NiSe₂/C/CF) through pyrolysis and selenization processes. NiSe₂/C/CF displays a higher HER performance than that of Ni/C/CF and Ni-MOF-74/CF. Notably, the NiSe₂/C/CF electrode gives a low overpotential of 209 mV, a Tafel slope of 74.1 mV/dec, and outstanding stability with slight decay after operating for 12 h. The high HER catalytic activity of NiSe₂/C/CF is mainly ascribed to the emerging effects of NiSe₂ nanoparticles and three-dimensional conductive substrate CF, facilitating active moieties exposure and electron transfer during the electrocatalytic process. Therefore, this work illustrates a novel approach for the preparation of transition metal chalcogenides as low-cost and stable catalysts for HER.     

Nanoscale engineering MoP/Fe2P/RGO toward efficient electrocatalyst for hydrogen evolution reaction

The preparation of hydrogen evolution reaction (HER) electrocatalyst with high catalytic performance is a huge challenge. In this work, we develop a MoP/Fe₂P/RGO composite as a electrocatalyst for HER. The MoP/Fe₂P/RGO exhibits excellent electrocatalytic performance with a Tafel slope and an onset overpotential of 51 mV/dec and 105 mV, respectively. To drive 10 mA/cm², it only requires a small over-potential of 156 mV. The high electrocatalytic HER activity is mainly due to the synergistic effect of MoP and Fe₂P. In addition, the introduction of RGO not only prevents particle aggregation and coalescence during high temperature phosphating, but also improves the conductivity of the catalyst.     

Interface regulation of Pt quantum dots doped nickel phosphide and cobalt hydroxide to promote electrocatalytic overall water splitting

The transition metal phosphates are earth-abundant minerals that have been shown to perform well in electrocatalytic water splitting, whereas these catalysts still tend to have excessively high overpotentials and slow kinetics in HER and OER processes. In the present work, hybrid catalysts consisting of Pt quantum dots doped NiP (NiP-Pt) nano-embroidery spheres and Co(OH)₂ nanosheets were successfully prepared by two-step electrodeposition method. The excellent catalytic performance of the catalyst relies principally on the synergistic interaction between NiP and Pt quantum dots. Additionally, the NiP-Pt exhibits strong electronic interactions at the interface with Co(OH)₂. Consequently, the catalyst has a strong catalytic performance in terms of HER and OER catalytic performance. In terms of HER, an overpotential of only 40 mV is required when the current density reaches 10 mA cm^?2, corresponding to a Tafel slope of 49.85 mV·dec^?1. At the same time, the catalyst also performs well at OER, with a current density of 10 mA cm^?2 at an overpotential of 186 mV and a Tafel slope of 53.049 mV·dec^?1 much less than most electrocatalysts. This study involving electrodeposition and doping of quantum dots provides a new idea for the efficient synthesis of fundamental HER and OER bifunctional catalysts.     

Self-supported molybdenum selenide nanosheets grown on urchin-like cobalt selenide nanowires array for efficient hydrogen evolution

The development of a highly efficient hybrid catalyst is desirable for the water splitting to produce hydrogen. MoSe₂ is one of the low-cost candidates; however, its activity for hydrogen evolution reaction (HER) is still not satisfactory due to the low conductivity and poor electrical contact with the charge collection substrate. Herein, we provide a simple approach of synthesizing vertically aligned MoSe₂ nanoplatelets on the urchin-like HER-active conductive CoSe₂ nanowire array. Nanostructured MoSe₂/CoSe₂ hybrid catalysts obtained a current density of 10 mA cm⁻² at overpotentials of only 129 mV, with a small Tafel slope of 38.2 mV dec⁻¹, which is superior to those of most transition metal dichalcogenides (MoSe₂, MoSe₂–CoSe₂ hybrids, and so on). The abundant exposed active sites of MoSe₂, as well as an efficient electrical contact between MoSe₂ nanosheets and CoSe₂ nanowires, which is beneficial for the outstanding HER performance of MoSe₂/CoSe₂ hybrid electrode.     

In-situ grown of Ni2P nanoparticles on 2D black phosphorus as a novel hybrid catalyst for hydrogen evolution

Nickel phosphide-based nanomaterials have been acted as efficient catalysts for the hydrogen evolution reaction (HER), however, the design of novel and high performance HER catalyst is still a challenge. Herein, we report a novel 2D material black phosphorus (BP) as support for constructing Ni₂P-based hybrid catalyst by a one-pot thermal decomposition approach. TEM results indicated that the monodispersed Ni₂P nanoparticles with small size and good dispersion supported on the surface of layered BP, which implied that more catalytic active sites may be exposed for HER. The as-synthesized Ni₂P/BP hybrid exhibits high HER electrocatalytic performance with low onset overpotential (70 mV), small Tafel slope (81 mV dec^?1), large double-layer capacitance (1.24 mF cm^?2), high conductivity and good stability, which can be assigned to the strong synergistic effect between Ni₂P and BP. Therefore, BP may be a suitable support for constructing excellent catalysts in electrocatalysis.     

Enhanced hydrogen evolution reaction of WS2–CoS2 heterostructure by synergistic effect

Transition metal dichalcogenides (TMDs) have attracted significant research interest due to its promising performance in hydrogen evolution reaction (HER). Synergistic effect between materials interface can improve the electrocatalytic properties. In this work, the WS₂–CoS₂ heterostructure supported on carbon paper (CP) was elaborately fabricated by a three-step method. Owing to the synergistic effect, WS₂–CoS₂ heterostructure exhibits an excellent electrocatalytic activity with a low overpotential of 245 mV at 100 mA/cm² and a small Tafel slope of 270 mV/dec toward HER. We demonstrate that the increased specific surface area and conductivity of the heterostructure play a key role in enhancing the overall catalytic efficiency. Moreover, the crystal lattice distortion in the heterostructure could induce charge redistribution and improve electron transfer efficiency, which may also benefit the whole HER activity.     

Atmosphere plasma treatment and Co heteroatoms doping on basal plane of colloidal 2D VSe2 nanosheets for enhanced hydrogen evolution

Structural engineering of highly efficient electrocatalysts based on 2D transition metal dichalcogenides (TMDs) for hydrogen evolution reaction (HER) is of great significance for sustainable energy conversion processes. Herein, a novel basal-plane engineering of 2D colloidal VSe₂ nanosheets has been developed for highly enhanced HER performance via a synergistic combination of atmosphere plasma (AP) treatment and Co basal-plane doping. Systematic experiments and theoretical calculations show that the AP treatment not only efficiently removes the organic ligands, but also introduces defects and cracks as more active sites on the basal plane; while the Co basal-plane doping and defects further optimize Gibbs free energy of hydrogen adsorbed on the Se sites. Such AP treated 5 % Co doped VSe₂ electrocatalyst exhibits onset overpotential of only 160 mV, Tafel slope of 42 mV/decade and turnover frequency (TOF) of 6.4 S⁻¹ at 260 mV, comparable to the most active TMDs electrocatalysts. This work provides fresh insights into the utilization of “clean surface”, defects/cracks and heteroatom doping on basal plane of 2D nanosheets for catalytic application.     

Facile preparing composite of CoSe2 wrapping N-doped mesoporous carbon with highly electrocatalytic activity for hydrogen evolution reaction

The composites of cobalt selenide (CoSe₂) wrapping nitrogen self-doped mesoporous graphitic carbon were facilely prepared by hydrothermally wrapping CoSe₂ on the carbon material derived from pyrolysis of N-containing zeolitic imidazolate framework. The composites exhibit excellent catalytic activities and durability for electrochemical hydrogen evolution reaction (HER) in 0.5 M H₂SO₄. The optimum composite catalyst needs only low overpotential of 159 mV to approach 10 mA/cm² and as low as 83 mV/dec of Tafel slope can be obtained. The results are among the most active for HER based on non-noble materials in acidic solution.     

Performance evaluation of molybdenum dichalcogenide (MoX2; X= S,Se, Te) nanostructures for hydrogen evolution reaction

Hydrogen evolution reaction (HER) using transition metal dichalcogenides (TMDs) have gained interest owing to their low-cost, abundancy and predominant conductivity. However, forthright comparisons of transition metal chalcogenides for HER are scarcely conducted. In this work, we report the synthesis of series of molybdenum chalcogenide nanostructures MoX₂ (X = S, Se, Te) via a facile hydrothermal method. Used as an electrocatalyst for HER, MoS₂ nanograins, MoSe₂ nanoflowers and MoTe₂ nanotubes could afford the benchmark current densities of 10 mA cm⁻² at the overpotentials of −173 mV, −208 mV and −283 mV with the measured Tafel slope values of 109.81 mV dec⁻¹, 65.92 mV dec⁻¹ and 102.06 mV dec⁻¹, respectively. Besides other factors influencing HER, the role of electronic conductivity in HER of these molybdenum dichalcogenides are elucidated. In addition, the presented molybdenum dichalcogenides in this work are also complimented with robustness as determined from high-current density stability measurements.     

Design of Ni/NiO–TiO2/rGO nanocomposites on carbon cloth conductors via PECVD for electrocatalytic water splitting

The facile synthesis and design of noble metal-free efficient catalysts to accelerate the sluggish kinetics of the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is still a big challenge for electrolytic water splitting. In that context, the preparation of efficient catalysts with superior catalytic activity from cheap raw materials on a large scale is crucial. Briefly, Ni/NiO/TiO₂/rGO is designed using the environmental-friendly and easily up-scalable PECVD technique. This trinary composite presents significance in regulating the crystalline structure, composition and electronic properties towards superior HER and OER activity in acidic solution as bifunctional electrocatalysts for efficient water splitting. Together with the promising long-term stability and durability, Ni/NiO/TiO₂/rGO displays excellent electrocatalytic activity towards HER with η₁₀ of 130 mv vs RHE and a Tafel slope of 40 mV/dec.     

A new hyperbranched water-splitting technique based on Co3O4/MoS2 nano composite catalyst for High-Performance of hydrogen evolution reaction

Due to the extensive use of fossil fuels & their direct influence on the environment, new ways of producing energy sources are highly needed. Hydrogen is the perfect candidate for renewable energy; however, H₂ gas production is associated with disadvantages due to a lack of efficient and active catalysts that could be cost-effective and comparable to platinum performance. Active hydrogen evolution reaction catalysts are needed to advance the development of a cheaper generation of solar fuels. Thus, outperformance, and stable earth abundant. And inexpensive catalysts are highly demanded. That is H₂ gas production from the electrolysis of water through HER. In this work, we present different analytical techniques that characterize an efficient and highly stable catalyst based on transition metal oxide Co₃O₄/MoS₂ nanostructures. And their composites for water splitting in harsh acidic conditions time and material chemical composition as like SEM, EDS, XRD, HRTEM & XPS. The composite material is highly best to produce HER at 10 mA cm^?2 and obtained 268 mV overpotential of nano Co₃O₄/MoS₂ (S3) and Tafel slope of 56 mv/dec. Faraday efficiencies of the hydrogen gas production measured for the 60 min and catalyst is highly durable for the 20 h. The presented catalysts are up to the mark of platinum metal performance and superior to several transition metal oxides. This fabrication technology is a new roadmap for developing active and scalable hydrogen-evolving catalysts by overcoming the issues of fewer catalytic edges, low density, and poor conductivity.     

Tungsten-molybdenum oxide nanowires/reduced graphene oxide nanocomposite with enhanced and durable performance for electrocatalytic hydrogen evolution reaction

Hydrogen has attracted huge interest globally as a durable, environmentally safe and renewable fuel. Electrocatalytic hydrogen evolution reaction (HER) is one of the most promising methods for large scale hydrogen production, but the high cost of Pt-based materials which exhibit the highest activity for HER forced researchers to find alternative electro-catalyst. In this study, we report noble metal free a 3D hybrid composite of tungsten-molybdenum oxide and reduced graphene oxide (GO) prepared by a simple one step hydrothermal method for HER. Benefitting from the synergistic effect between tungsten-molybdenum oxide nanowires and reduced graphene oxide, the obtained W-Mo-O/rGO nanocomposite showed excellent electro-catalytic activity for HER with onset potential 50 mV, a Tafel slope of 46 mV decade^?1 and a large cathodic current, while the tungsten-molybdenum oxide nanowires itself is not as efficient HER catalyst. Additionally, W-Mo-O/rGO composite also demonstrated good durability up to 2000 cycles in acidic medium. The enhanced and durable hydrogen evolution reaction activity stemmed from the synergistic effect broadens noble metal free catalysts for HER and provides an insight into the design and synthesis of low-cost and environment friendly catalysts in electrochemical hydrogen production.     

Highly efficient electrocatalytic hydrogen production via MoSx/3D-graphene as hybrid electrode

Molybdenum sulfide (MoS_x) has recently emerged as a promising catalyst for the hydrogen evolution reaction (HER) in water splitting that may replace the noble metal, such as platinum, as a cost-effective and high catalytic materials. It has been reported that two-dimensional structured MoS_x exhibit significant amount of exposed S-edge, which can be an active electrocatalytic catalyst for hydrogen production. However, the current reports mainly focusing on the planar electrode, where the catalyst utilization and the number of active sites are limited due to the lower exposed specific surface area (SSA) of supporting electrodes. In this work, we utilize the freeze-drying method to produce a porous three-dimensional (3D) structure assembled by graphene flakes. The as-prepared 3D graphene scaffold shows high surface area, high porosity while low density, which makes it as an ideal conductive electrode for supporting of MoS_x catalysts. Moreover, it was found out that the crystallinity of MoS_x, controlled by thermolysis temperature of thiosalts precursor ((NH₄)₂MoS₄), shows significantly influence the performance of HER. The optimized annealing temperature for the designed hybrid electrodes (MoS_x/3D-graphene) was found to create a lot of active sites, which facilitate the electrocatalytic performance for water splitting (overpotential of 163 mV @10 mA/cm² and a Tafel slope of 41 mV/dec). The study provides a potential material, which could pave the way for future applications of hydrogen energy.     

Extraordinarily high hydrogen-evolution-reaction activity of corrugated graphene nanosheets derived from biomass rice husks

The metal-free carbonaceous catalysts are one of the promising candidates for efficient electrocatalytic hydrogen production. Aiming at demonstrating the high electrocatalytic activity of the hydrogen evolution reaction (HER), we synthesized the biomass rice husk-derived corrugated graphene (RH-CG) nanosheets via the KOH activation. The 700 °C-activated RH-CG nanosheets exhibited the large specific surface area as well as the high electrical conductivity. When using the RH-CG nanosheets as a HER electrocatalyst in 0.5 M H₂SO₄, the excellent HER activities with a small overpotential (9 mV at 10 mA/cm²) and a small Tafel slope (31 mV/dec) were achieved. The results provide a new strategy for materializing the superb biomass-derived electrocatalyst for highly efficient hydrogen production.     

Growth of iron diselenide nanorods on graphene oxide nanosheets as advanced electrocatalyst for hydrogen evolution reaction

Advanced electrocatalysts for the fabrication of sustainable hydrogen from water splitting are innermost to energy research. Herein, we report the growth of iron diselenide (FeSe₂) nanorods on graphene oxide (GO) sheets using two-step process viz., simple hydrothermal reduction and followed by wet chemical process. The orthorhombic phase of FeSe₂ incorporated GO nanosheet was developed as a low-cost and efficient electrocatalyst for hydrogen evolution reaction (HER) by water splitting. The phase purity, crystalline structure, surface morphology and elemental composition of the synthesized samples have been investigated by UV–visible absorption spectroscopy (UV–vis), fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray analysis (EDS). Voltammetry and Tafel polarization methods have been utilized to assess the performance of various weight ratio of GO nanosheet in FeSe₂ nanorods towards H₂ evolution. Detailed electrochemical investigations revealed that the 30% FeSe₂/GO composite showed a tremendous electrocatalytic HER activity in acidic medium with high cathodic current density of 9.68 mA/cm² at η = 250 mV overpotential and with a Tafel slope of 64 mV/dec. The 30% FeSe₂/GO composite offers a high synergistic effect towards HER activity, which is mainly due to high electrochemical active catalytic sites, low charge-transfer resistance and enhanced electrocatalytic performances of H₂ production. The present analysis revealed the possible application of FeSe₂/GO composite as a promising low-cost alternative to platinum based electrocatalysts for H₂ production.     

Meritorious spatially on hierarchically Co3O4/MoS2 phase nanocomposite synergistically a high-efficient electrocatalyst for hydrogen evolution reaction performance: Recent advances & future perspectives

Hydrogen is zero-emission fuel production for a clean environment as alternative effective the energy source is still moreover, an effective challenge in near future due to the lack of efficient and inexpensive catalysts. An efficient electrocatalysts structure having logical design which holds a paramount significance for the hydrogen evolution reaction (HER) but rarely noble metal Pt-like activity achieved by the transition metal oxides electrocatalysts based on oxides matured and cooperative with coupling metal oxides could be considered as a desired substitute electrocatalysts to change Pt/C based nano composite materials. Herein, un-noble the metal oxides of hetero structure consisting of Co₃O₄/MoS₂ based-electrocatalysts nanocomposite material. The desirable out-comes show that Co₃O₄/MoS₂ composite material providing extraordinary efficient HER kinetics activity in different experimental designs. The Co₃O₄/MoS₂ based electro-catalyst increases the best activity of HER kinetics performance especially measured in 1 M KOH solution condition and offers an influential interfacing engineering strategy at very minute over potential of 348 mV evaluated and small Tafel slopes 46 mV/dec for HER performance. This work elucidates interest for efficient electrocatalysts for a broader range of scalable applications in the development of renewable energies, the functional materials such as solar cells, lithium sulphur-batteries and energy chemistry advancing.     

High-performance alkaline hydrogen evolution of NiMoP2 nanowire boosted by bimetallic synergic effect

Hydrogen evolution reaction (HER) in alkaline conditions usually requires a higher overpotential compared with acidic conditions due to the extra energy barrier originating from the additional water dissociation step. In this work, the theoretical calculation has confirmed that this challenge can be solved by the bimetallic synergic effect on binary transition metal catalysts. We report a simple method to synthesize NiMoP₂ nanowires with (100) plane which can precisely expose Ni and Mo atom. The synthesized NiMoP₂ nanowires exhibit a small overpotential of 87 mV to reach 10 mA cm⁻² with a low Tafel slope of 66 mV dec⁻¹ and long-term stability in alkaline solutions.