Active Basal Planes Research Articles

Two-dimensional platinum borides: A Dirac nodal line quantum electrocatalyst for efficient hydrogen evolution reaction

Two-dimensional (2D) catalysts exhibiting high carrier mobility, near-zero Gibbs free energy (ΔGH*), and an active basal plane are highly desirable for optimizing the hydrogen evolution reaction (HER). However, fusing these attributes within a solitary material encounters profound difficulties. Utilizing density functional theory (DFT) calculations, we have identified the PtB2 monolayer is such a candidate, demonstrating exceptional dynamical, thermal, and mechanical stability. The band structure analysis reveals that the PtB2 monolayer features double Dirac points along its high-symmetry lines. The estimated Fermi velocity of the PtB2 monolayer is as high as 7.8×105m/s, close to that of graphene. By scanning the Dirac points in the first Brillouin Zone, the Dirac points constitute a nodal-line semimetal with a loop centered at the Γ point. This nodal line is anticipated to facilitate charge transfer between the catalyst surfaces and reaction intermediates, potentially enhancing catalytic efficiency. Importantly, PtB2 monolayer boasts superior HER performance, with a nearly zero ΔGH* of 0.057 eV at its boron-dominant sites. The application of a subtle 1% strain serves to reduce its ΔGH* to an even more favorable −0.003 eV, suggesting significantly improved HER capabilities. When layered in a bilayer form, the PtB2 exhibits van der Waals (vdW) type interlayer interactions. Remarkably, we found that varying the stacking order can effectively alter the nodal line's shape and, accordingly, the PtB2 layer's catalytic properties. The distinctive combination of a Dirac nodal line, ideal Gibbs free energy, and expansive active sites positions the PtB2 monolayer as a competitive 2D quantum catalyst for hydrogen production.

Nanotubes and other nanostructures of VS2, WS2, and MoS2: Structural effects on the hydrogen evolution reaction

Vanadium sulfide (VS2) is a layered transition metal dichalcogenide (TMD), comparable in crystal structure to the well-known MoS2 and WS2. Theoretical predictions attribute much potential to VS2, since it is metallic-like and has an active basal plane, essential for catalytic performance. However, it is much less studied than other members of the TMD family due to the difficulties in synthesizing specific structures with controlled properties. Here we present unique structures of VS2 nanotubes and conduct a comparative study with other well-known inorganic nanotubes and nanostructures of MoS2 and WS2. We evaluate the effect of the curvature and strain, the abundance of surface defects, and the availability of surface sites in various structures by electrochemical methods. We show that MoS2 has the best intrinsic activity, which is enhanced by an extensive electrochemical surface area. The woven-like structure of the MoS2 nanotube walls provides a combined effect of strain, crystallinity, and defects. For WS2 structures, the strained surface of the nanotubes results in sites with higher intrinsic activity than the edge sites, but structures such as the nano-triangles, which provide a higher number of edge sites, exhibit competing activity. As for the VS2 structures, although theoretical calculations predict optimal active sites for the hydrogen evolution reaction (HER), they are extremely sensitive to stoichiometry variations that hamper their catalytic activity. Our findings contribute insights to the improvement and design of VS2–based nanocatalysts for the HER and shed light on the general factors that govern the activity in the unique TMD nanotubes family.

Monolayer Ta2Se: A low-cost catalyst with enhanced stability and high basal plane activity for oxygen reduction reaction

The search for cost-effective two-dimensional (2D) electrocatalysts is accelerating as these materials emerge as pivotal alternatives to traditional energy technologies for fuel cells. In this work, we report a low-cost, high-performance Ta2Se monolayer as an electrocatalyst for the oxygen reduction reaction (ORR) through first-principles calculations. The Ta2Se monolayer exhibits notable stability and low cleavage energy, underscoring its practical potential for experimental synthesis. Our computations show that the Ta2Se monolayer has a metallic band structure with substantial electronic states at the Fermi level, which suggests the favorable electron transport properties. Remarkably, the outer Ta atoms in the basal plane of Ta2Se monolayer are identified as ORR active sites, exhibiting a competitive selection for dissociative and associative four-electron pathways alongside outstanding catalytic activity. Through examining the surface coverage impacts on ORR, we disclose that at a moderate oxygen coverage, the Ta2Se monolayer's limiting potential reaches approximately 0.9 eV, outstripping the conventional Pt electrodes, thus confirming its superior ORR catalytic capability. The low cost, active basal plane sites, and high ORR activity make the Ta2Se monolayer a competitive candidate for advanced fuel cell components.

Promotion of Sulfur Vacancies and Mn Substitution in Few-Layered Molybdenum Disulfide Towards Superior Hydrogen Evolution in Acid

The superior features of hydrogen as an energy source with high energy density (120 MJ kg-1) and zero CO2 emission, makes it a strong candidate for replacing fossil fuels. Recently the European Commission has pledged to invest €470 billion in renewable hydrogen technologies by 2050, with a significant portion of this investment expected to be allocated for the deployment of renewable hydrogen electrolyzers by 2030. Water electrolysis via Proton Exchange Membrane (PEM) with Pt/Pd-based noble metals as a cathode, is currently the most effective method for hydrogen production, but alternatives are highly needed due to the scarcity and the higher cost of these metals. One of the promising classes of electrocatalysts for hydrogen evolution reaction (HER) is transition metal dichalcogenides (TMDs), and among them molybdenum disulfide (MoS2) has shown promising properties as an electrocatalyst for hydrogen production. MoS2 has different phases of 1T, 2H, and 3R with 2H-MoS2 being the most promising electrocatalyst for hydrogen production due to its semiconductive behavior and long-term stability. However, the poor conductivity, large band gap and no active basal plane towards HER limits the applications of 2H-MoS2 for water electrolysis in PEM cells. Strategies such as introduction of defects, S-vacancies, edge engineering and doping can result in enhanced HER activity of 2H-MoS2. Incorporating different transition metals (Ni, Co, Mn, Fe) into MoS2 lattice can increase the number of active sites and improve charge transfer during the electrocatalytic reaction. Based on Density Functional Theory (DFT) studies, insertion of Mn into MoS2 layer can decrease the bandgap to zero, resulting in large number of available electronic states around the Fermi level. In this work we introduce Mn doped MoS2 produced via a cost-effective microwave-assisted solid-state approach to explore the potential of few-layered MoS2, doped with different levels of manganese (5%, 10% and 15% at.) for HER in acidic media. The electrocatalytic activity towards HER reveals that 10% at. Mn incorporation into MoS2 lattice, reduces the overpotential (η10) from 210 mV for pristine MoS2 to 148 mV for 10%Mn-MoS2, respectively. In addition, Tafel slope analysis has confirmed a faster kinetics of 10%Mn-MoS2 (53 mV dec-1) compared to MoS2 (75 mV dec-1) revealing the Volmer–Heyrovsky mechanism as the rate determining step (rds). Further characterization by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and DFT studies show that Mn substitution promotes the creation of sulfur vacancies, which in turn enhances the catalytic activity towards HER. Additionally, the 10% Mn-doped MoS2 demonstrates remarkable activity in a single-cell PEM electrolyzer with long-term durability. This study highlights the potential of Mn doped MoS2 as an efficient, low-cost electrocatalyst for hydrogen production, with implications for the development of a sustainable hydrogen economy. Figure 1

Combination strategy of large interlayer spacing and active basal planes for regulating the microwave absorption performance of MoS2/MWCNT composites at thin absorber level

Recently, molybdenum disulfide (MoS2)/carbon has become a promising candidate for efficient microwave absorption. However, it is still challenging to simultaneously optimize the synergy of impedance matching and loss capability at the level of a thin absorber. Here, a new adjustment strategy is proposed by changing the concentration of precursor l-cysteine for MoS2/multi-walled carbon nanotubes (MWCNT) composites to unlock the basal plane of MoS2 and expand the interlayer spacing from 0.62 nm to 0.99 nm, leading to improved packing of MoS2 nanosheets and more active sites. Therefore, the tailored MoS2 nanosheets exhibit abundant sulfur-vacancies, lattice-oxygen, more metallic 1T-phase, and higher surface area. Such sulfur-vacancies and lattice-oxygen promote the electronic asymmetric distribution at the solid-air interface of MoS2 crystals and induce stronger microwave attenuation through interface/dipole polarization, which is further verified by first-principles calculations. In addition, the expansion of the interlayer spacing induces more MoS2 to deposit on the MWCNT surface and increases the roughness, improving the impedance matching and multiple scattering. Overall, the advantage of this adjustment method is that while optimizing impedance matching at the thin absorber level, composite still maintains a high attenuation capacity, which means enhancing the attenuation performance of MoS2 itself offsets the weakening of the composite's attenuation ability caused by the decrease in the relative content of MWCNT components. Most importantly, adjusting impedance matching and attenuation ability can be easily implemented by separate control of l-cysteine content. As a result, the MoS2/MWCNT composites achieve a minimum reflection loss value of −49.38 dB and an effective absorption bandwidth of 4.64 GHz at a thickness of only 1.7 mm. This work provides a new vision for the fabrication of thin MoS2-carbon absorbers.

Interface modulation induced by the 1T Co-WS2 shell nanosheet layer at the metallic NiTe2/Ni core–nanoskeleton: Glib electrode-kinetics for HER, OER, and ORR

The metallic (1T) transition metal dichalcogenides (TMDCs) are known for their superior electrocatalytic performance, due to their high conductivity, active basal-planes, and exposed edges. Our novel approach of coupling a metallic-NiTe2/Ni nano-skeleton with 1T-Co-WS2 nanosheet in a core–shell arrangement to develop a hybrid heterostructure (1T Co-WS2/NiTe2/Ni) has helped to outperform the trifunctional-electrocatalytic activity (HER, OER, and ORR). 1T-Co-WS2/NiTe2/Ni only requires ultralow overpotential (ηHER = 88 mV@10, ηOER = 290 mV@30), higher half-wave potential for ORR (E1/2 = 0.781 V vs RHE), small Tafel slopes (HER = 68 mV dec-1, OER = 98 mV dec-1, and ORR = 63 mV dec-1) with high electrocatalytic surface area and robust stability in corresponding half-cell reactions. The designed heterostructured electrocatalyst (1T Co-WS2/NiTe2/Ni) presented exceptional total water-splitting performance, requiring a low voltage of 1.521 V to yield 10 mA cm−2 current with extensive structural and electrochemical durability. Such performance could be attributed towards improved nanochannel morphology with exposed active edge, fluent electrode-kinetics, facile adsorption–desorption of reaction intermediates owing to the intrinsically tuned 1T-WS2 by cobalt-doping, and hybridized NiTe2/Ni nano-skeleton. The DFT study confirmed that the incorporation of Co atoms in basal plane and the edge sites of WS2 lattice induces the redistribution and modulation of electronic structure for fast electron/charge transfer and the synergistic coupling of 1T NiTe2 heterostructures bolstered the electrocatalytic activity of the as-prepared catalysts. These outcomes provide a prospect towards the design and application of efficient 2D/2D heterostructured electrocatalyst for zero emission energy goal.

Fe 5 Ge 2 Te 2 : Iron‐rich Layered Chalcogenide for Highly Efficient Hydrogen Evolution

Recent research on van der Waals (vdW) metal chalcogenides electrocatalysts for the hydrogen evolution reaction (HER) has been devoted to finding new catalysts with active basal planes. Here, we report on experimental and theoretical investigations of the HER activity of a recently discovered iron-rich vdW spintronic material, Fe5Ge2Te2 (FG2T) in alkaline media (1 M KOH). We show that a densified electrode of FG2T requires an overpotential of only −90.5 mV to drive a current density of 10 mA/cm2. Free energy calculations of hydrogen adsorption using density functional theory (DFT) proved that the numerous sites present on the hexagonal Te layer are more active than those found in the recently proposed Fe3GeTe2 (FGT) catalyst, supporting higher activity for the new Fe-richer catalyst. Like in FGT, XPS analysis has found that a thin oxide layer covers the active FG2T layers, suggesting the real active surface to be a hybrid FG2T/oxide layer. These results strengthen the idea of continued screening of iron-based vdW materials to replace the non-abundant platinum group electrocatalysts toward HER and other electrocatalytic processes.

Bifunctional P-Intercalated and Doped Metallic (1T)-Copper Molybdenum Sulfide Ultrathin 2D-Nanosheets with Enlarged Interlayers for Efficient Overall Water Splitting.

Metallic (1T) molybdenum disulfide (MoS2) is a much better electrocatalyst than the semiconducting (2H) MoS2 because of its superior conductivity, presence of active basal planes, and bulky interlayers. However, the lack of thermodynamic stability has hindered its practical uses. The insertion of transition metals and nonmetals in the interlayers and the crystal is known to improve both the thermodynamic stability and the catalytic efficacy of 1T-MoS2. In this study, for the first time we have developed an electrocatalyst for water splitting based on metallic copper molybdenum sulfide (1T-CMS). The present catalyst, P-doped and intercalated 1T-CMS ultrathin 2D nanosheets on carbon cloth (P-1T-CMS@CC), demonstrates excellent catalytic efficacy for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). It required an overpotential of 95 mV for HER and of 284 mV for OER at a current density of 10 mA cm-2. The P-1T-CMS@CC(+ -) device also shows excellent performance, requiring a cell voltage of only 1.51 V at a current density of 10 mA cm-2.

P and Se-codopants triggered basal plane active sites in NbS2 3D nanosheets toward electrocatalytic hydrogen evolution

Promoting the intrinsic activity and accessibility of basal plane sites in transition metal dichalcogenides (TMDs) is an important way to optimize their catalytic performance for energy conversion and storage. Here, a simple liquid-phase phosphating selenization pyrolysis method is developed to prepare P and Se co-doped niobium disulfide (NbS2) 3D nanosheets with active basal plane for efficient catalyzing hydrogen evolution reaction (HER). Experimental results indicate that the P and Se co-doped NbS2 3D nanosheets exhibit significantly enhanced HER activity and stability compared to their undoped counterparts. It realizes 165 mV decreased overpotential at 10 mA cm−2 and a stable durability over 40 h continuous operation at 14 mA cm−2 without observable fading. Density functional theory (DFT) studies suggest that the P dopant is to activate the adjacent original inert Nb sites, where both S and Nb sites in P, Se co-doped NbS2 monolayer can together act as the active sites for HER. Furthermore, the addition of selenium can stabilize the catalytic activity. Our work provides a promising approach and theoretical framework for improving the electrocatalytic HER performance of NbS2, and may have general guidelines for other transition metal disulfides.

Directly anchoring non-noble metal single atoms on 1T-TMDs with tip structure for efficient hydrogen evolution

Owing to tip effect can introduce localized enhanced electric field and reduce interfacial energy barrier, design of atomic tip structure in single-atom catalysts (SACs) may be a fascinating strategy to further improve its electrocatalytic activity. However, conventional synthesis methods, such as defect-trapping or substitution, only lead to the formation of planar geometry of SACs without tip atoms. Good conductive 1T-TMDs with electrocatalytically active basal plane can provide platform to directly stabilize single atoms (SAs) on the top sites of its surface to form atomic tip structure. Herein, a universal Laser-molecular beam epitaxy (L-MBE) method for precisely controlling non-noble metal SAs directly immobilizing on the Cr top site of 1T-CrS2 metallic basal plane is developed. In case of Mo, the Mo SAs@1T-CrS2 with single-atom tip structure can exhibit enhanced electric field surrounding Mo atoms and an almost zero hydrogen adsorption free energy, resulting in superior HER performance together with high stability. This work provides a general way to design varieties of SACs in widely catalytic application.

MX Anti-MXenes from Non-van der Waals Bulks for Electrochemical Applications: The Merit of Metallicity and Active Basal Plane.

Two-dimensional transition-metal compounds (2DTMCs) are promising materials for electrochemical applications, but 2DTMCs with metallicity and active basal planes are rare. In this work, we proposed a simple and effective strategy to extract 2DTMCs from non-van der Waals bulk materials and established a material library of 79 2DTMCs, which we named as anti-MXenes since they are composed of one M atomic layer sandwiched by two X atomic layers. By means of density functional theory computations, 24 anti-MXenes were confirmed to be thermodynamically, dynamically, mechanically, and thermally stable. The metallicity and active basal plane endow these anti-MXenes with potential as excellent electrode materials, for example, as electrocatalysts for hydrogen evolution reactions (HER). Among the noble-metal free anti-MXenes with favorable H-binding, CuS can boost HER at the whole range of H coverages, while CoSi, FeB, CoB, and CoP show promise for HER at some specific H coverages. The active sites are the tetra-coordinating nonmetal atoms at the basal planes, thus rendering a very high density of active sites for these materials. CoB is also a promising anode material for lithium-ion batteries, showing low Li diffusion energy barriers, a very high capacity, and a suitable open circuit voltage. This work promotes the "computational exfoliation" of 2D materials from non-van der Waals bulks and exemplifies the applications of anti-MXenes in various electrochemical processes.

Hierarchical fibrous bimetallic electrocatalyst based on ZnO-MoS2 composite nanostructures as high performance for hydrogen evolution reaction

To understand new fundamental questions related to electrocatalyst design to achieve very efficient and stable nonprecious catalysts for water splitting and to strengthen renewable energy reservoirs and nonprecious nanocomposites for efficient water splitting will strengthen the renewable energy reservoirs, thereby it will bring more sustainable and environment friendly society with minimum global warming effect. The synthesized nanocomposite material demonstrates efficient catalytic kinetics for HER, due to the exposure of best active edge sites of MoS 2. The as prepared the nanocomposite was characterized successfully by XRD, SEM, TEM, XPS & EDS were executed that elucidates the crystalline nature of the synthesized nanocomposite material. In an acidic medium, ZnO 30% providing the best ZnO-MoS 2 content achieved at 0.26 V. The ZnO-MoS 2 Tafel slope is 56 mV/decades the ever reported for hydrogen production in an acidic media for ZnO-MoS 2 -based electrocatalysts. The electrocatalyst exhibit excellent stability and durability. Chronopotentiometry at 10 mA/cm 2 current density suffers not a significant loss in the potential for 10 h in an acidic media, respectively. The sample of less ZnO concentration results in increased catalytic properties for MoS 2 , by providing active basal planes for hydrogen evolution reaction along with Mo and S-edges, as predicted by theoretical studies. Interestingly, the catalyst material, architecture and use of nanostructured catalysts have been found useful for improving the efficiency by showing high active reaction sites and the electrical connection of these sites for swift charge kinetics. Therefore, the morphology and structure of fabricated electrocatalysts can have advantageous features for catalysis performance. These findings provide a new stable and efficient electrocatalysts for the development of electro catalyzer devices for the hydrogen gas production based on cost-effective methodology and earth-abundant materials. This work will open a new gateway for the development of functional catalysts in renewable energy reservoirs, which will be scientifically significant and will also provide a roadmap for the development of industrial catalysts.

Enhancement of basal plane electrocatalytic hydrogen evolution activity via joint utilization of trivial and non-trivial surface states

Transition metal dichalcogenide semiconductors, particularly MoS2, are known as promising alternative non-precious hydrogen evolution reaction (HER) electrocatalysts to high-cost Pt. However, their performance is strongly limited by the poor conductivity and lack of active sites in the basal plane. Therefore, it is desirable to find alternatives with active basal plane sites or develop facile strategies to optimize the inert basal plane. In this work, we study the HER over topological semimetal Nb2S2C based on its basal plane. We report the first successful activation and optimization of the basal plane of Nb2S2C by synergistic using trivial surface states (SSs) and nontrivial topological surface states (TSSs). We find that the binding strength towards hydrogen adsorption of the easily cleaved sulfur(S)-terminated Nb2S2C surface can be stronger than that of 2H-MoS2, attributing to the presence of trivial SSs and nontrivial TSSs in Nb2S2C. By creating S vacancy on the basal plane, the binding strength towards hydrogen adsorption can be greatly optimized. The TSSs together with dangling-bonds reduce the Gibbs free energy to 0.31 eV, close to the peak of the volcano plot. This study provides a promising strategy for the joint utilization of the basal plane trivial SSs and TSSs for the HER.

Unveiling active sites by structural tailoring of two‐dimensional niobium disulfide for improved electrocatalytic hydrogen evolution reaction

Here we report, unveiling the active sites for improved electrocatalytic hydrogen evolution reaction (HER) by structural tailoring of Niobium Disulfide (NbS2). NbS2 synthesized by chemical vapor deposition method, structural deformation is carried out by post-argon plasma and annealing treatment. Plasma-treated (P.T) NbS2 exhibits layer-by-layer stacked (≈250 nm) long and (≈200 nm) wide flakes, which show more edge sites and demonstrates low hydrogen evolution activity. Annealed NbS2 flakes are enlarged in size (≈1 μm) having more surface area which shows additional active basal plane sites and demonstrate remarkable HER performance at 10 mA cm−2. As the thickness of NbS2 is reduced, more basal planes are exposed hence improved HER activity was achieved. This enhanced electrocatalytic change demonstrates that the basal planes are the main active sites for HER in NbS.

High-Throughput Identification of Exfoliable Two-Dimensional Materials with Active Basal Planes for Hydrogen Evolution

Two-dimensional (2D) materials with intrinsically active basal planes are promising alternative catalysts to the Pt-group noble metals for large-scale hydrogen production. Herein, we perform a comp...

Covalent doping of Ni and P on 1T-enriched MoS2 bifunctional 2D-nanostructures with active basal planes and expanded interlayers boosts electrocatalytic water splitting

Fabrication of 1T-Ni0.2Mo0.8S1.8P0.2 nanoflowers and 1T-Ni0.2Mo0.8S1.8P0.2 freestanding nanosheets with active basal planes and expanded interlayers as superior bifunctional electrocatalysts for water splitting.

Design of basal plane active MoS2 through one-step nitrogen and phosphorus co-doping as an efficient pH-universal electrocatalyst for hydrogen evolution

The exploration of low-cost, stable, and highly active noble-metal-free electrocatalyst for hydrogen evolution reaction (HER) in a wide pH range is crucial but still challenging task for renewable energy techniques. MoS2-based materials have been considered as a promising electrocatalyst for HER. However, corresponding studies have been hampered by the lack of effective routes to fully utilize the large number of inert basal plane for catalyzing HER, especially under alkaline media. Herein, a novel ammonia ions-guided-nitrogenization-phosphorization strategy is developed to prepare N and P co-doped MoS2 with active basal plane for efficient catalyzing HER with a quite low overpotential of 116 and 78 mV in 0.5 M H2SO4 and 1.0 M KOH to achieve a current density of 10 mA cm−2, respectively. Experimental studies and theoretical calculations confirm Mo-N-P sites in the basal plane of MoS2 can not only accelerate HER kinetics, but also result in energetic favorability and structure stability. Furthermore, outstanding performances are also obtained under both sea and river water, vastly broadening the application prospects.

Template-Driven Phase Selective Formation of Metallic 1T-MoS2 Nanoflowers for Hydrogen Evolution Reaction

The exploration of MoS2 based catalyst has been growing over the recent years, mainly focusing on fine-tuning the metallic phases for improved catalytic activity in the hydrogen evolution reaction (HER). Considering the synthesis of MoS2, the 2H phase (trigonal prismatic, D3h) is more stable than the 1T phase (octahedral, Oh). Still, with the increased electronic conductivity, hydrophilic nature, and the presence of electrochemically active basal planes, the 1T phase shows enhanced catalytic activity compared to the 2H phase which shows semiconducting nature with only edge sites being active. So far, one of the best ways to synthesize 1T-MoS2 is the alkali metal exfoliation, but a setback to this method is that there are many issues like intercalation of alkali ions, self-heating, and pyrophoric nature associated with it. Moreover it requires undesirable and expensive organic solvent to produce 1T phase. The aqueous phase synthesis of 1T-MoS2 is still hampered by the low extent of 1T enrichment and reprod...

Active basal plane in ZT-phased MX2 (M = Mo, W; X = S, Se, Te) catalysts for the hydrogen evolution reaction: A theoretical study

Two-dimensional layered structure of Transition Metal Dichalcogenides (TMDs), MoS2 for example, show superior performance of catalysis for hydrogen evolution reaction (HER) as noble-metal free catalysts. However, the active sites of 2H-phased TMDs mainly located at the edge of layered structures, and the basal planes of the materials present inert properties. Therefore, the increase of active sites and improvement of catalytic efficiency for hydrogen evolution reaction by TMDs are of significant importance in the clean energy production. In this study, we identify that the ZT phase of TMDs can be outstanding candidates for HER catalysts by employing density functional theory (DFT), and the phase transition from 2H to ZT can be achieved by mechanical deformations. We obtained the free energy ΔGH of ZT phased MoSe2 and WS2 are −0.04 eV and 0.03 eV, respectively, suggesting promising HER activity of the two systems. Moreover, the HER activity is further analyzed by p-band center theory and the hydrogen coverage effect on the HER performance is evaluated as well. This study opens a new window for the application of 2D ZT-phased TMDs and provides a new class of candidates for noble metal-free catalysts for HER.

Hydrogen Evolution Catalyzed by a Molybdenum Sulfide Two-Dimensional Structure with Active Basal Planes.

Molybdenum disulfide has been demonstrated as a promising catalyst for hydrogen evolution reaction (HER). However, its performance is limited by fractional active edge sites and the strong dependence on hydrogen coverage. In this study, we find an enhanced HER performance in a two-dimensional substoichiometric molybdenum sulfide. Both first-principles calculations and experimental results demonstrate that the basal plane is catalytically active toward HER, as evidenced by an optimum Gibbs free energy and a low reaction overpotential. More interestingly, the HER performance is insensitive to hydrogen coverage and can be improved under compressive in-plane biaxial strains. Our results suggest not only an improved HER performance of substoichiometric molybdenum sulfide due to its chemical reactive basal plane but also a way to tune the performance.