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Why BET surface area smaller but materials have higher HER activety for MoS2?

Electrochemistry

Oxygen evolution

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The smaller BET surface area of MoS2 materials can paradoxically result in higher hydrogen evolution reaction (HER) activity due to specific structural features. Smaller MoS2 nanosheets with a high electrochemical active surface area and edge sites exhibit superior HER performance compared to larger sizes, showcasing lower overpotentials and Tafel slopes . Strategies to enhance HER activity in MoS2 involve activating the inert basal plane, increasing active edge sites, and improving conductivity through defect engineering and carbon supports . Additionally, MoS2 nanosheet arrays supported on hollow rGO spheres demonstrate enhanced HER performance due to expanded interlayer spacing and exposed electroactive edges, despite a smaller BET surface area . These findings highlight that specific structural characteristics and defect engineering play crucial roles in enhancing HER activity, even with a smaller BET surface area in MoS2 materials.

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Open access•Journal Article•DOI Electrochemical and SECM Investigation of MoS2/GO and MoS2/rGO Nanocomposite Materials for HER Electrocatalysis Sriram Kumar, Prasanta Kumar Sahoo, Ashis K. Satpati, Ashis K. Satpati - Show less +3 more 02 Nov 2017 36 Citations	The higher HER activity of MoS2/GO despite smaller BET surface area suggests catalytic current is influenced by inherent characteristics of the catalyst's substrate rather than just surface area.
Journal Article•DOI Defects Enhance the Electrocatalytic Hydrogen Evolution Properties of MoS 2 -based Materials Yaojia Cheng, Haoqiang Song, Han Wu, Panke Zhang, Zhiyong Tang, Siyu Lu - Show less +5 more 16 Oct 2020-Chemistry-an Asian Journal 39 Citations	Defects in MoS2 materials enhance HER activity by activating the inert basal plane, increasing active edge sites, and improving conductivity, compensating for the smaller BET surface area.
Open access•Journal Article•DOI One-Step Preparation of Large Area Films of Oriented MoS2 Nanoparticles on Multilayer Graphene and Its Electrocatalytic Activity for Hydrogen Evolution Jinbao He, Cristina Fernández, Ana Primo, Hermenegildo García - Show less +3 more 22 Jan 2018-Materials 220 Citations	The higher hydrogen evolution reaction (HER) activity of MoS2 despite a smaller BET surface area is attributed to the loading, particle size, and amount of exposed active sites influencing catalytic activity.
Open access•Journal Article•DOI MoS 2 Nanosheet Arrays Rooted on Hollow rGO Spheres as Bifunctional Hydrogen Evolution Catalyst and Supercapacitor Electrode Shizheng Zheng, Lijun Zheng, Zhengyou Zhu, Jian Chen, Jianli Kang, Zhulin Huang, Dachi Yang - Show less +6 more 09 Jul 2018-Nano-micro Letters 86 Citations	The enhanced hydrogen evolution reaction (HER) activity of MoS2 despite a smaller BET surface area is due to expanded interlayer spacing and increased conductivity in the hierarchical architecture.
Open access•Journal Article•DOI Size Effects of MoS2 on Hydrogen and Oxygen Evolution Reaction 28 Feb 2022-Journal of electrochemical science and technology 5 Citations	The smaller MoS2 nanosheets have higher HER activity despite a smaller BET surface area due to their high electrochemical active surface area with edge sites, enhancing catalytic behavior.

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Related Questions

How does doping affect the electrical properties of MoS2?5 answersDoping significantly impacts the electrical properties of MoS2. Area-selective doping using 1,2-dichloroethane (DCE) solution enhances field-effect mobility and reduces subthreshold swing, leading to improved performance. N-type doping with poly (vinylidene fluoride-co-trifluoroethylene) (P (VDF-TrFE)) and polar polymer increases field effect mobility, shifts the threshold voltage negatively, and boosts the on-current in MoS2 field-effect transistors. Doping with various elements alters the band gap of MoS2, with halogen non-metals inducing n-type conduction, showcasing the tunability of MoS2 for semiconductor applications. Transition metal (TM) and nitrogen (N) mono-doping and co-doping reduce the band gap, introduce impurity levels, and enable infrared light photoresponse, enhancing the potential of MoS2 in IR photodetectors and photovoltaic devices. Overall, doping plays a crucial role in tailoring the electrical properties of MoS2 for diverse electronic applications.

Mo vacancy meaning in MoS2?5 answersIn the context of MoS2, a Mo vacancy refers to a vacancy in the lattice structure where a molybdenum (Mo) atom is missing. These vacancies significantly impact the properties of monolayer MoS2. The presence of Mo vacancies can induce chalcogen vacancies, affecting the material's behavior and properties. Mo vacancies can also serve as active sites for catalytic reactions, such as CO oxidation, when doped with other atoms like Co. Understanding the behavior and mobility of vacancies, such as S-vacancies, is crucial for optimizing the catalytic activity of MoS2-based materials. Operando spectroscopy techniques have been used to study the formation and impact of clustered S-vacancies on the basal plane of MoS2, shedding light on their electronic and geometric structures.

Can mos2 be tuned by the stark effect?4 answersYes, molybdenum disulfide (MoS2) can be tuned by the Stark effect. The Stark effect refers to the shift in energy levels of excitons in response to an applied electric field. In the case of MoS2, the quantum confined Stark effect (QCSE) can be observed, where the exciton can be polarized by a vertical electric field. This polarization leads to a quadratic shift in the photoluminescence emission energies of the excitons with the applied electric field. The tuning range achieved is about 120 meV, indicating a significant control over the exciton transition energy. The exciton polarizability, which quantifies the response of the exciton to the electric field, has been measured to be (7.8 ± 1.0) × 10–10 D m V–1 for neutral excitons and (6.4 ± 0.9) × 10–10 D m V–1 for charged excitons in MoS2. These findings demonstrate the potential for manipulating the optical properties of MoS2 through the Stark effect.

What is the significance of MoS2 in metal-CO2 batteries?5 answersMoS2 is significant in metal-CO2 batteries because it acts as a catalyst to improve the performance of the battery. The MoS2/SnS2 composite cathode catalyst reduces the overpotential and improves the cyclic stability of Na-CO2 batteries. The MoS2/NCF framework serves as a substrate for Na deposition in sodium-metal batteries, enabling uniform Na deposition and controlled Na diffusion. Ni1/MoS2 catalysts exhibit high catalytic activity for CO2 reduction reactions, making them suitable for CO2RR to methanol. Additionally, Mo2C-CNTs catalytic cathodes in Mg-CO2 batteries reduce the charge overpotential and improve the selectivity towards MgC2O4, resulting in exceptional low voltage hysteresis. Overall, MoS2 plays a crucial role in enhancing the performance and efficiency of metal-CO2 batteries.

How MoS2 is acting as catalyst for metal air batteries?5 answersMoS2 acts as a catalyst for metal-air batteries by promoting the formation and decomposition of discharge products during the charging and discharging cycle, specifically the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The catalytic activity of MoS2 is enhanced by its unique electronic structures, which enable fast reaction kinetics, high electrical transport rate, and proliferated catalytic active sites. Additionally, MoS2 nanosheets encapsulated in a Mo-N/C framework with interfacial Mo-N coupling centers exhibit robust multifunctional electrocatalytic activity and stability, making them highly efficient cathode electrocatalysts for metal-air batteries. The hierarchical pore framework of MoS2 allows for fast mass transport, contributing to its outstanding electrocatalytic properties. Overall, MoS2-based electrocatalysts show promise for the development of high-performance and cost-effective metal-air batteries.

How can the photoluminescence of MoS2 be enhanced through defect engineering and oxygen bonding?5 answersThe photoluminescence (PL) of MoS2 can be enhanced through defect engineering and oxygen bonding. The introduction of oxygen doping and defect passivation effectively suppresses the nonradiative recombination of excitons, leading to enhanced radiative recombination and PL properties of MoS2. Additionally, plasmon-induced electron injection into MoS2 can increase the overall signal intensity and blue shift the PL spectrum. Furthermore, the layer sequence in heterostructures can significantly affect the PL enhancement, with MoS2 supported by photochemically functionalized graphene (F-G/MoS2) showing a 5-fold PL enhancement compared to MoS2 stacked underneath F-G (MoS2/F-G). The photoluminescent properties of MoS2 nanosheets can also be improved through chemical functionalization, which is of high practical importance for enhancing MoS2 PL properties. Finally, the optimal energy band alignment in van der Waals heterostructures can preserve the light emission of MoS2 and enhance its photoluminescence intensity.

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