Superior Hydrogen Evolution Reaction Performance in 2H‐MoS2 to that of 1T Phase

In the hydrogen evolution reaction (HER), energy‐level matching is a prerequisite for excellent electrocatalytic activity. Conventional strategies such as chemical doping and the incorporation of defects underscore the complicated process of controlling the doping species and the defect concentration, which obstructs the understanding of the function of band structure in HER catalysis. Accordingly, 2H‐MoS₂ and 1T‐MoS₂ are used to create electrocatalytic nanodevices to address the function of band structure in HER catalysis. Interestingly, it is found that the 2H‐MoS₂ with modulated Fermi level under the application of a vertical electric field exhibits excellent electrocatalytic activity (as evidenced by an overpotential of 74 mV at 10 mA cm^?2 and a Tafel slope of 99 mV per decade), which is superior to 1T‐MoS₂. This unexpected excellent HER performance is ascribed to the fact that electrons are injected into the conduction band under the condition of back‐gate voltage, which leads to the increased Fermi level of 2H‐MoS₂ and a shorter Debye screen length. Hence, the required energy to drive electrons from the electrocatalyst surface to reactant will decrease, which activates the 2H‐MoS₂ thermodynamically.     

Interface Modulation of MoS2/Metal Oxide Heterostructures for Efficient Hydrogen Evolution Electrocatalysis

Developing efficient earth‐abundant MoS₂ based hydrogen evolution reaction (HER) electrocatalysts is important but challenging due to the sluggish kinetics in alkaline media. Herein, a strategy to fabricate a high‐performance MoS₂ based HER electrocatalyst by modulating interface electronic structure via metal oxides is developed. All the heterostructure catalysts present significant improvement of HER electrocatalytic activities, demonstrating a positive role of metal oxides decoration in promoting the rate‐limited water dissociation step for the HER mechanism in alkaline media. The as‐obtained MoS₂/Ni₂O₃H catalyst exhibits a low overpotential of 84 mV at 10 mA cm^?2 and small charge‐transfer resistance of 1.5 Ω in 1 m KOH solution. The current density (217 mA cm^?2) at the overpotential of 200 mV is about 2 and 24 times higher than that of commercial Pt/C and bare MoS₂, respectively. Additionally, these MoS₂/metal oxides heterostructure catalysts show outstanding long‐term stability under a harsh chronopotentiometry test. Theoretical calculations reveal the varied sensitivity of 3d‐band in different transition oxides, in which Ni‐3d of Ni₂O₃H is evidently activated to achieve fast electron transfer for HER as the electron‐depletion center. Both electronic properties and energetic reaction trends confirm the high electroactivity of MoS₂/Ni₂O₃H in the adsorption and dissociation of H₂O for highly efficient HER in alkaline media.     

Interface Density Engineering on Heterogeneous Molybdenum Dichalcogenides Enabling Highly Efficient Hydrogen Evolution Catalysis and Sodium Ion Storage

Constructing active heterointerfaces is powerful to enhance the electrochemical performances of transition metal dichalcogenides, but the interface density regulation remains a huge challenge. Herein, MoO₂/MoS₂ heterogeneous nanorods are encapsulated in nitrogen and sulfur co-doped carbon matrix (MoO₂/MoS₂@NSC) by controllable sulfidation. MoO₂ and MoS₂ are coupled intimately at atomic level, forming the MoO₂/MoS₂ heterointerfaces with different distribution density. Strong electronic interactions are triggered at these MoO₂/MoS₂ heterointerfaces for enhancing electron transfer. In alkaline media, the optimal material exhibits outstanding hydrogen evolution reaction (HER) performances that significantly surpass carbon-covered MoS₂ nanorods counterpart (η₁₀: 156 mV vs 232 mV) and most of the MoS₂-based heterostructures reported recently. First-principles calculation deciphers that MoO₂/MoS₂ heterointerfaces greatly promote water dissociation and hydrogen atom adsorption via the O–Mo–S electronic bridges during HER process. Moreover, benefited from the high pseudocapacitance contribution, abundant “ion reservoir”-like channels, and low Na⁺ diffusion barrier appended by high-density MoO₂/MoS₂ heterointerfaces, the material delivers high specific capacity of 888 mAh g⁻¹, remarkable rate capability and cycling stability of 390 cycles at 0.1 A g⁻¹ as the anode of sodium ion battery. This work will undoubtedly light the way of interface density engineering for high-performance electrochemical energy conversion and storage systems.     

Gram‐Scale Aqueous Synthesis of Stable Few‐Layered 1T‐MoS2: Applications for Visible‐Light‐Driven Photocatalytic Hydrogen Evolution

Most recently, much attention has been devoted to 1T phase MoS₂ because of its distinctive phase‐engineering nature and promising applications in catalysts, electronics, and energy storage devices. While alkali metal intercalation and exfoliation methods have been well developed to realize unstable 1T‐MoS₂, but the aqueous synthesis for producing stable metallic phase remains big challenging. Herein, a new synthetic protocol is developed to mass‐produce colloidal metallic 1T‐MoS₂ layers highly stabilized by intercalated ammonium ions (abbreviated as N‐MoS₂). In combination with density functional calculations, the X‐ray diffraction pattern and Raman spectra elucidate the excellent stability of metallic phase. As clearly depicted by high‐angle annular dark‐field imaging in an aberration‐corrected scanning transmission electron microscope and extended X‐ray absorption fine structure, the N‐MoS₂ exhibits a distorted octahedral structure with a 2a ₀ × a ₀ basal plane superlattice and 2.72 Å Mo–Mo bond length. In a proof‐of‐concept demonstration for the obtained material's applications, highly efficient photocatalytic activity is achieved by simply hybridizing metallic N‐MoS₂ with semiconducting CdS nanorods due to the synergistic effect. As a direct outcome, this CdS:N‐MoS₂ hybrid shows giant enhancement of hydrogen evolution rate, which is almost 21‐fold higher than pure CdS and threefold higher than corresponding annealed CdS:2H‐MoS₂.     

Structure Engineering of MoS2 via Simultaneous Oxygen and Phosphorus Incorporation for Improved Hydrogen Evolution

Oxygen and phosphorus dual‐doped MoS₂ nanosheets (O,P‐MoS₂) with porous structure and continuous conductive network are fabricated using a one‐pot NaH₂PO₂‐assisted hydrothermal approach. By simply changing the precursor solution, the chemical composition and resulting structure can be effectively controlled to obtain desired properties toward the hydrogen evolution reaction (HER). Thanks to the beneficial structure and strong synergistic effects between the incorporated oxygen and phosphorus, the optimal O,P‐MoS₂ exhibit superior electrocatalytic performances compared with those of oxygen single‐doped MoS₂ nanosheets (O‐MoS₂). Specifically, a low HER onset overpotential of 150 mV with a small Tafel slope of 53 mV dec^?1, excellent conductivity, and long‐term durability are achieved by the structural engineering of MoS₂ via O and P co‐doping, making it an efficient HER electrocatalyst for water electrocatalysis. This work provides an alternative strategy to manipulate transition metal dichalcogenides as advanced materials for electrocatalytic and related energy applications.     

Aligned Heterointerface‐Induced 1T‐MoS2 Monolayer with Near‐Ideal Gibbs Free for Stable Hydrogen Evolution Reaction

1T‐phase molybdenum disulfide (1T‐MoS₂) exhibits superior hydrogen evolution reaction (HER) over 2H‐phase MoS₂ (2H‐MoS₂). However, its thermodynamic instability is the main drawback impeding its practical application. In this work, a stable 1T‐MoS₂ monolayer formed at edge‐aligned 2H‐MoS₂ and a reduced graphene oxide heterointerface (EA‐2H/1T/RGO) using a precursor‐in‐solvent synthesis strategy are reported. Theoretical prediction indicates that the edge‐aligned layer stacking can induce heterointerfacial charge transfer, which results in a phase transition of the interfacial monolayer from 2H to 1T that realizes thermodynamic stability based on the adhesion energy between MoS₂ and graphene. As an electrocatalyst for HER, EA‐2H/1T/RGO displays an onset potential of ?103 mV versus RHE, a Tafel slope of 46 mV dec^?1 and 10 h stability in acidic electrolyte. The unexpected activity of EA‐2H/1T/RGO beyond 1T‐MoS₂ is due to an inherent defect caused by the gliding of S atoms during the phase transition from 2H to 1T, leading the Gibbs free energy of hydrogen adsorption (ΔG_H*) to decrease from 0.13 to 0.07 eV, which is closest to the ideal value (0.06 eV) of 2H‐MoS₂. The presented work provides fundamental insights into the impressive electrochemical properties of HER and opens new avenues for phase transitions at 2D/2D hybrid interfaces.     

A Universal Strategy for Intimately Coupled Carbon Nanosheets/MoM Nanocrystals (M = P,S, C,and O) Hierarchical Hollow Nanospheres for Hydrogen Evolution Catalysis and Sodium‐Ion Storage

Intimately coupled carbon/transition‐metal‐based hierarchical nanostructures are one of most interesting electrode materials for boosting energy conversion and storage applications owing to the strong synergistic effect between the two components and appealing structural stability. Herein, a universal method is reported for making hierarchical hollow carbon nanospheres (HCSs) with intimately coupled ultrathin carbon nanosheets and Mo‐based nanocrystals. The in situ and confined reaction of the synthetic strategy can not only allow the aggregation of the nanocrystals to be impeded, but also endows extremely intimate coupled interaction between the conductive carbon nanosheets and the nanocrystals MoM (M = P, S, C and O). As a proof of concept, the as‐prepared MoP/C HCSs exhibit extraordinary hydrogen evolution reaction electrocatalytic activity with small overpotential and robust durability in both acidic and alkaline solutions. In addition, the unique sheet‐on‐sheet MoS₂/C HCSs as an anode demonstrate high capacity, great rate capabilities, and long‐term cycles for sodium‐ion batteries (SIBs). The capacity can be maintained at 410 mA h g^?1 even after 1000 cycles even at a high current density of 4 A g^?1, one of the best reported values for MoS₂‐based electrode materials for SIBs. The present work highlights the importance of designing and fabricating functional strongly coupled hybrid materials for enhancing energy conversion and storage applications.     

Coupling Interface Constructions of MoS2/Fe5Ni4S8 Heterostructures for Efficient Electrochemical Water Splitting

Water splitting is considered as a pollution‐free and efficient solution to produce hydrogen energy. Low‐cost and efficient electrocatalysts for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) are needed. Recently, chemical vapor deposition is used as an effective approach to gain high‐quality MoS₂ nanosheets (NSs), which possess excellent performance for water splitting comparable to platinum. Herein, MoS₂ NSs grown vertically on FeNi substrates are obtained with in situ growth of Fe₅Ni₄S₈ (FNS) at the interface during the synthesis of MoS₂. The synthesized MoS₂/FNS/FeNi foam exhibits only 120 mV at 10 mA cm^?2 for HER and exceptionally low overpotential of 204 mV to attain the same current density for OER. Density functional theory calculations further reveal that the constructed coupling interface between MoS₂ and FNS facilitates the absorption of H atoms and OH groups, consequently enhancing the performances of HER and OER. Such impressive performances herald that the unique structure provides an approach for designing advanced electrocatalysts.     

Engineering 2D Metal–Organic Framework/MoS2 Interface for Enhanced Alkaline Hydrogen Evolution

2D metal–organic frameworks (MOFs) have been widely investigated for electrocatalysis because of their unique characteristics such as large specific surface area, tunable structures, and enhanced conductivity. However, most of the works are focused on oxygen evolution reaction. There are very limited numbers of reports on MOFs for hydrogen evolution reaction (HER), and generally these reported MOFs suffer from unsatisfactory HER activities. In this contribution, novel 2D Co‐BDC/MoS₂ (BDC stands for 1,4‐benzenedicarboxylate, C₈H₄O₄) hybrid nanosheets are synthesized via a facile sonication‐assisted solution strategy. The introduction of Co‐BDC induces a partial phase transfer from semiconducting 2H‐MoS₂ to metallic 1T‐MoS₂. Compared with 2H‐MoS₂, 1T‐MoS₂ can activate the inert basal plane to provide more catalytic active sites, which contributes significantly to improving HER activity. The well‐designed Co‐BDC/MoS₂ interface is vital for alkaline HER, as Co‐BDC makes it possible to speed up the sluggish water dissociation (rate‐limiting step for alkaline HER), and modified MoS₂ is favorable for the subsequent hydrogen generation step. As expected, the resultant 2D Co‐BDC/MoS₂ hybrid nanosheets demonstrate remarkable catalytic activity and good stability toward alkaline HER, outperforming those of bare Co‐BDC, MoS₂, and almost all the previously reported MOF‐based electrocatalysts.     

Nickel@Nitrogen‐Doped Carbon@MoS2 Nanosheets: An Efficient Electrocatalyst for Hydrogen Evolution Reaction

Developing cheap, abundant, and easily available electrocatalysts to drive the hydrogen evolution reaction (HER) at small overpotentials is an urgent demand of hydrogen production from water splitting. Molybdenum disulfide (MoS₂) based composites have emerged as competitive electrocatalysts for HER in recent years. Herein, nickel@nitrogen‐doped carbon@MoS₂ nanosheets (Ni@NC@MoS₂) hybrid sub‐microspheres are presented as HER catalyst. MoS₂ nanosheets with expanded interlayer spacings are vertically grown on nickel@nitrogen‐doped carbon (Ni@NC) substrate to form Ni@NC@MoS₂ hierarchical sub‐microspheres by a simple hydrothermal process. The formed Ni@NC@MoS₂ composites display excellent electrocatalytic activity for HER with an onset overpotential of 18 mV, a low overpotential of 82 mV at 10 mA cm^?2, a small Tafel slope of 47.5 mV dec^?1, and high durability in 0.5 H₂SO₄ solution. The outstanding HER performance of the Ni@NC@MoS₂ catalyst can be ascribed to the synergistic effect of dense catalytic sites on MoS₂ nanosheets with exposed edges and expanded interlayer spacings, and the rapid electron transfer from Ni@NC substrate to MoS₂ nanosheets. The excellent Ni@NC@MoS₂ electrocatalyst promises potential application in practical hydrogen production, and the strategy reported here can also be extended to grow MoS₂ on other nitrogen‐doped carbon encapsulated metal species for various applications.     

Stabilizing the MXenes by Carbon Nanoplating for Developing Hierarchical Nanohybrids with Efficient Lithium Storage and Hydrogen Evolution Capability

The MXenes combining hydrophilic surface, metallic conductivity and rich surface chemistries represent a new family of 2D materials with widespread applications. However, their poor oxygen resistance causes a great loss of electronic properties and surface reactivity, which significantly inhibits the fabrication, the understanding of the chemical nature and full exploitation of the potential of MXene‐based materials. Herein we report a facile carbon nanoplating strategy for efficiently stabilizing the MXenes against structural degradation caused by spontaneous oxidation, which provides a material platform for developing MXene‐based materials with attractive structure and properties. Hierarchical MoS₂/Ti₃C₂‐MXene@C nanohybrids with excellent structural stability, electrical properties and strong interfacial coupling are fabricated by assembling carbon coated few‐layered MoS₂ nanoplates on carbon‐stabilized Ti₃C₂ MXene, exhibiting exceptional performance for Li storage and hydrogen evolution reaction (HER). Remarkably, ultra‐long cycle life of 3000 cycles with high capacities but extremely slow capacity loss of 0.0016% per cycle is achieved for Li storage at a very high rate of 20 A g^?1. They are also highly active HER electrocatalyst with very positive onset potential, low overpotential and long‐term stability in acidic solution. Superb properties highlight the great promise of MXene‐based materials in cornerstone applications of energy storage and conversion.     

Balancing Volmer Step by Superhydrophilic Dual-Active Domains for Enhanced Hydrogen Evolution

The reaction kinetics of hydrogen evolution reaction (HER) is largely determined by balancing the Volmer step in alkaline media. Bifunctionality as a proposed strategy can divide the work of water dissociation and intermediates (OH* and H*) adsorption/desorption. However, sluggish OH* desorption plagues water re-adsorption, which leads to poisoning effects of active sites. Some active sites may even directly act as spectators and do not participate in the reaction. Furthermore, the activity comparison under approximate nanostructure between bifunctional effect and single-exposed active sites is not fully understood. Here, a facile three-step strategy is adopted to successfully grow molybdenum disulfide (MoS₂) on cobalt-containing nitrogen-doped carbon nanotubes (Co-NCNTs), forming obvious dual active domains. The active sites on domains of Co-NCNTs and MoS₂ and the tuned electronic structure at the heterointerface trigger the bifunctional effect to balance the Volmer step and improve the catalytic activity. The HER driven by the bifunctional effect can significantly optimize the Gibbs free energy of water dissociation and hydrogen adsorption, resulting in fast reaction kinetics and superior catalytic performance. As a result, the Co-NCNTs/MoS₂ catalyst outperforms other HER electrocatalysts with low overpotential (58 and 84 mV at 10 mA cm⁻² in alkaline and neutral conditions, respectively), exceptional stability, and negligible degradation.     

Highly Robust Non‐Noble Alkaline Hydrogen‐Evolving Electrocatalyst from Se‐Doped Molybdenum Disulfide Particles on Interwoven CoSe2 Nanowire Arrays

Developing efficient non‐noble and earth‐abundant hydrogen‐evolving electrocatalysts is highly desirable for improving the energy efficiency of water splitting in base. Molybdenum disulfide (MoS₂) is a promising candidate, but its catalytic activity is kinetically retarded in alkaline media due to the unfavorable water adsorption and dissociation feature. A heterogeneous electrocatalyst is reported that is constructed by selenium‐doped MoS₂ (Se‐MoS₂) particles on 3D interwoven cobalt diselenide (CoSe₂) nanowire arrays that drives the hydrogen evolution reaction (HER) with fast reaction kinetics in base. The resultant Se‐MoS₂/CoSe₂ hybrid exhibits an outstanding catalytic HER performance with extremely low overpotentials of 30 and 93 mV at 10 and 100 mA cm^–2 in base, respectively, which outperforms most of the inexpensive alkaline HER catalysts, and is among the best alkaline catalytic activity reported so far. Moreover, this hybrid catalyst shows exceptional catalytic performance with very low overpotentials of 84 and 95 mV at 10 mA cm^–2 in acidic and neutral electrolytes, respectively, implying robust pH universality of this hybrid catalyst. This work may provide new inspirations for the development of high‐performance MoS₂‐based HER electrocatalysts in unfavorable basic media for promising catalytic applications.     

3D 1T‐MoS2/CoS2 Heterostructure via Interface Engineering for Ultrafast Hydrogen Evolution Reaction

Metallic phase (1T) MoS₂ has been regarded as an appealing material for hydrogen evolution reaction. In this work, a novel interface‐induced strategy is reported to achieve stable and high‐percentage 1T MoS₂ through highly active 1T‐MoS₂/CoS₂ hetero‐nanostructure. Herein, a large number of heterointerfaces can be obtained by interlinked 1T‐MoS₂ and CoS₂ nanosheets in situ grown from the molybdate cobalt oxide nanorod under moderate conditions. Owing to the strong interaction between MoS₂ and CoS₂, high‐percentage of metallic‐phase (1T) MoS₂ of 76.6% can be achieved, leading to high electroconductivity and abundant active sites compared to 2H MoS₂. Furthermore, the interlinked MoS₂ and CoS₂ nanosheets can effectively disperse the nanosheets so as to enlarge the exposed active surface area. The near zero free energy of hydrogen adsorption at the heterointerface can also be achieved, indicating the fast kinetics and excellent catalytic activity induced by heterojunction. Therefore, when applied in hydrogen evolution reaction (HER), 1T‐MoS₂/CoS₂ heterostructure delivers low overpotential of 71 and 26 mV at the current density of 10 mA cm^?2 with low Tafel slops of 60 and 43 mV dec^?1, respectively in alkaline and acidic conditions.     

Surface Engineering of MoS2 via Laser‐Induced Exfoliation in Protic Solvents

With excellent performance in the hydrogen evolution reaction (HER), molybdenum disulfide (MoS₂) is considered a promising nonprecious candidate to substitute Pt‐based catalysts. Herein, pulsed laser irradiation in liquid is used to realize one‐step exfoliation of bulk 2H‐MoS₂ to ultrastable few‐layer MoS₂ nanosheets. Such prepared MoS₂ nanosheets are rich in S vacancies and metallic 1T phase, which significantly contribute to the boosted catalytic HER activity. Protic solvents play a pivotal role in the production of S vacancies and 2H‐to‐1T phase transition under laser irradiation. MoS₂ exfoliated in an optimal solvent of formic acid exhibits outstanding HER activity with an overpotential of 180 mV at 10 mA cm^?2 and Tafel slope of 54 mV dec^?1.     

Facile and Scalable Mechanochemical Synthesis of Defective MoS2 with Ru Single Atoms Toward High-Current-Density Hydrogen Evolution

Designing a facile strategy to prepare catalysts with highly active sites are challenging for large-scale implementation of electrochemical hydrogen production. Herein, a straightforward and eco-friendly method by high-energy mechanochemical ball milling for mass production of atomic Ru dispersive in defective MoS₂ catalysts (Ru₁@D-MoS₂) is developed. It is found that single atomic Ru doping induces the generation of S vacancies, which can break the electronic neutrality around Ru atoms, leading to an asymmetrical distribution of electrons. It is also demonstrated that the Ru₁@D-MoS₂ exhibits superb alkaline hydrogen evolution enhancement, possibly attributing to this electronic asymmetry. The overpotential required to deliver a current density of 10 mA cm⁻² is as low as 107 mV, which is much lower than that of commercial MoS₂ (C-MoS₂, 364 mV). Further density functional theory (DFT) calculations also support that the vacancy-coupled single Ru enables much higher electronic distribution asymmetry degree, which could regulate the adsorption energy of intermediates, favoring the water dissociation and the adsorption/desorption of H*. Besides, the long-term stability test under 500 mA cm⁻² further confirms the robust performance of Ru₁@D-MoS₂. Our strategy provides a promising and practical way towards large-scale preparation of advanced HER catalysts for commercial applications.     

In Situ Synthesis of MoP Nanoflakes Intercalated N‐Doped Graphene Nanobelts from MoO3–Amine Hybrid for High‐Efficient Hydrogen Evolution Reaction

Molybdenum phosphide (MoP) is a promising non‐noble‐metal electrocatalyst in the hydrogen evolution reaction (HER), but practical implementation is impeded by the sluggish HER kinetics and poor chemical stability. Herein, a novel high‐efficiency HER electrocatalyst comprising MoP nanoflakes intercalated nitrogen‐doped graphene nanobelts (MoP/NG), which are synthesized by one‐step thermal phosphiding organic–inorganic hybrid dodecylamine (DDA) inserted MoO₃ nanobelts, is reported. The intercalated DDA molecules are in situ carbonized into the NG layer and the sandwiched MoO₃ layer is converted into MoP nanoflakes which are intercalated between the NG layers forming the alternatingly stacked MoP/NG hybrid nanobelts. The MoP nanoflakes provide abundant edge sites and the sandwiched MoP/NG hybrid enables rapid ion/electron transport thus yielding excellent electrochemical activity and stability for HER. The MoP/NG shows a low overpotential of 94 mV at 10 mA cm⁻², small Tafel slope of 50.1 mV dec⁻¹, and excellent electrochemical stability with 99.5% retention for over 22 h.     

Unveiling Active Sites for the Hydrogen Evolution Reaction on Monolayer MoS2

Here, the hydrogen evolution reaction (HER) activities at the edge and basal‐plane sites of monolayer molybdenum disulfide (MoS₂) synthesized by chemical vapor deposition (CVD) are studied using a local probe method enabled by selected‐area lithography. Reaction windows are opened by e‐beam lithography at sites of interest on poly(methyl methacrylate) (PMMA)‐covered monolayer MoS₂ triangles. The HER properties of MoS₂ edge sites are obtained by subtraction of the activity of the basal‐plane sites from results containing both basal‐plane and edge sites. The catalytic performances in terms of turnover frequencies (TOFs) are calculated based on the estimated number of active sites on the selected areas. The TOFs follow a descending order of 3.8 ± 1.6, 1.6 ± 1.2, 0.008 ± 0.002, and 1.9 ± 0.8 × 10^?4 s^?1, found for 1T′‐, 2H‐MoS₂ edges, and 1T′‐, 2H‐MoS₂ basal planes, respectively. Edge sites of both 2H‐ and 1T′‐MoS₂ are proved to have comparable activities to platinum (≈1–10 s^?1). When fitted into the HER volcano plot, the MoS₂ active sites follow a trend distinct from conventional metals, implying a possible difference in the reaction mechanism between transition‐metal dichalcogenides (TMDs) and metal catalysts.     

Penne‐Like MoS2/Carbon Nanocomposite as Anode for Sodium‐Ion‐Based Dual‐Ion Battery

The dual‐ion battery (DIB) system has attracted great attention owing to its merits of low cost, high energy, and environmental friendliness. However, the DIBs based on sodium‐ion electrolytes are seldom reported due to the lack of appropriate anode materials for reversible Na⁺ insertion/extraction. Herein, a new sodium‐ion based DIB named as MoS₂/C‐G DIB using penne‐like MoS₂/C nanotube as anode and expanded graphite as cathode is constructed and optimized for the first time. The hierarchical MoS₂/C nanotube provides expanded (002) interlayer spacing of 2H‐MoS₂, which facilitates fast Na⁺ insertion/extraction reaction kinetics, thus contributing to improved DIB performance. The MoS₂/C‐G DIB delivers a reversible capacity of 65 mA h g^?1 at 2 C in the voltage window of 1.0–4.0 V, with good cycling performance for 200 cycles and 85% capacity retention, indicating the feasibility of potential applications for sodium‐ion based DIBs.     

P and Se Binary Vacancies and Heterostructures Modulated MoP/MoSe2 Electrocatalysts for Improving Hydrogen Evolution and Coupling Electricity Generation

It is not enough to develop an ideal hydrogen evolution reaction (HER) electrocatalysts by single strategy. Here, the HER performances are significantly improved by the combined strategies of P and Se binary vacancies and heterostructure engineering, which is rarely explored and remain unclear. As a result, the overpotentials of MoP/MoSe₂-H heterostructures rich in P and Se binary vacancies are 47 and 110 mV at 10 mA cm⁻² in 1 m KOH and 0.5 m H₂SO₄ electrolytes, respectively. Especially, in 1 m KOH, the overpotential of MoP/MoSe₂-H is very close to commercial Pt/C at the beginning and even better than Pt/C when current density is over 70 mA cm⁻². The strong interactions between MoSe₂ and MoP facilitate electrons transfer from P to Se. Thus, MoP/MoSe₂-H possesses more electrochemically active sites and faster charge transfer capability, which are all in favor of high HER activities. Additionally, Zn-H₂O battery with MoP/MoSe₂-H as cathode is fabricated for simultaneous generation of hydrogen and electricity, which displays the maximum power density of up to 28.1 mW cm⁻² and stable discharging performance for 125 h. Overall, this work validates a vigorous strategy and provides guidance for the development of efficient HER electrocatalysts.