Recent progress and strategies of non-noble metal electrocatalysts based on MoS2/MOF for the hydrogen evolution reaction in water electrolysis: an overview
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Abstract
Recently, hydrogen has emerged as a prominent energy source that can be used in various technologies. Molybdenum disulfide (MoS2) is a typical catalyst material with two-dimensional groups that exhibit Pt-like hydrogen evolution reaction (HER) performance. In addition, metal-organic frameworks (MOFs) are a group of materials with ultrahigh porosity and enormous internal surface area, which are also highly beneficial for electrochemical processes. Therefore, catalysts based on MoS2 and MOF materials have been extensively investigated for the production of hydrogen gases. Numerous studies have indicated that a combination of MoS2 and MOF materials can dramatically boost the catalytic activity of these heterostructures. In this paper, the unique properties of MoS2 and MOF materials and the progress and strategies to improve the HER efficiency of catalysts based on MoS2/MOF hybrid materials are discussed. Furthermore, the challenges and future perspectives of these catalysts for HER are presented.
Keywords
INTRODUCTION
Over the last few decades, the overuse of fossil fuels, such as coal, oil, and petroleum products, has become a critical challenge due to numerous unexpected phenomena, including global warming, greenhouse effects, drought, and flooding[1,2]. As technologies rapidly develop, many smart devices and materials have been employed to overcome the energy crisis, including green energy, energy-saving, and renewable energy technologies[3-10]. Among them, hydrogen has various advantages such as environmental friendliness, earth abundance, high energy density, and renewability material[11-14]. Therefore, hydrogen can be used in many fields such as fertilizers, transportation, green energy, hydrogen power stations, and energy storage. To date, numerous methods have been studied to improve the efficiency of the hydrogen evolution reaction (HER) process[15,16]. In the last decade, conventional techniques, such as water electrolysis, have remained the most popular route for hydrogen production. Using low voltage, water molecules can be decomposed into oxygen and hydrogen. The efficiency of the process is highly dependent on the properties of the electrode materials where the gas can be released. Therefore, effective electrode materials that can boost the hydrolysis rate are desirable. In the past, noble metals, such as platinum group metals, have been used to produce hydrogen gas because of their fast kinetics, low hydrogen binding energy, and superb intrinsic conductivity[17,18]. However, there are also drawbacks to these groups, including scarce and expensive materials, as well as poor stability of these materials on an industrial scale.
Researchers have been intensively investigating the preparation of other catalysts with superior stability that could be alternatives to noble metals[18-20]. At the cutting edge of catalyst technologies, transition metal dichalcogenide (TMD) and metal-organic framework (MOF) materials have been intensively studied for the HER because of their unique properties and catalytic activity[21-25]. Molybdenum disulfide (MoS2) is one of the most typical TMD materials, exhibiting various advantages. MoS2 is significantly cheaper and more abundant than Pt, making it a more economical choice for large-scale applications. Additionally, MoS2 demonstrates excellent catalytic activity, especially in HER, and its properties can be further enhanced through methods such as doping or creating nanostructures, including low cost and remarkable catalytic stability[26-28]. MOF can provide a large surface area for the absorption-desorption process, which is the main process in the water electrolysis reaction[29,30]. The combination of MoS2 and MOF materials used to prepare the heterostructure catalyst for the HER is illustrated in Figure 1. These heterostructures provide numerous benefits for hydrogen technology and electrocatalytic applications. The properties, structural engineering, and HER performance of MoS2, MOF, and hybrid catalysts based on MoS2/MOF will be discussed in this paper. In addition, the challenges and future prospects of MoS2/MOF catalysts are briefly presented.
Figure 1. Electrocatalysts for HER application based on heterostructure MOF/MoS2 materials.
HYDROGEN EVOLUTION REACTION
Mechanism
Water splitting occurs when a small potential is applied. Electrochemical hydrolysis is used to produce hydrogen gas. Figure 2A shows the mechanism of the water-splitting process using an electrochemical technique[31]. Hydrolysis releases oxygen at the anode and hydrogen at the cathode. The theoretical free energy of water splitting is 1.23 eV at 25 °C and pressure of 1 atm. Because of the kinetic barrier for the reaction, the applied potential should be higher than 1.23 eV to overcome the kinetic barrier, and the process can proceed[32].
Figure 2. (A) Water splitting mechanism[31]. Copyright 2020, American Chemical Society. (B) HER mechanism[33]. Copyright 2018, Springer Nature. (C) Role of catalyst[39]. Copyright 2012. American Chemical Society. (D) Hydrogen binding energy of various materials[40]. Copyright 2005, American Chemical Society.
In the electrochemical hydrolysis process, the reaction mechanism is complicated and highly dependent on the electrolyte and/or electrode materials. Various mechanisms have been proposed and discussed in the literature. As shown in Figure 2B, different mechanisms of the HER can occur in acidic and alkaline media[33]. The mechanism of the HER is highly dependent on the media conditions in which the two-electron transfer process can occur at the cathode. The following three steps can be described for acidic media[34,35]:
The first is the Volmer step (1a), which produces adsorbed hydrogen. The HER can then proceed via the Heyrovsky step (1b), Tafel step (1c), or both to produce H2.
In an alkaline environment, two steps can occur: the Volmer step (2a) and the Heyrovsky step (2b).
Catalysts play a critical role in chemical processes. By using catalysts, the energy consumed for chemical reactions can be dramatically decreased, and the rate of the reaction can be significantly boosted[36-38]. Several studies have shown that the sluggish reaction kinetics of the HER, because of its high overpotential and small active surface area, are the main barriers to practical hydrogen production. The effects of the catalyst are illustrated in Figure 2C[39]. Therefore, it is challenging to produce hydrogen from commercial materials. Among the numerous non-noble metal catalysts, MoS2 is one of the most well-known two-dimensional catalysts, possessing numerous active sites and good catalytic activity. As shown in Figure 2D, the free energy of MoS2 is calculated and compared with different materials, which show a small free energy similar to that of Pt materials[40].
HER parameters
Various parameters must be considered to evaluate the performance of catalysts. Four crucial factors are often calculated to evaluate and compare the catalytic activities, as shown in Figure 3.
Figure 3. HER parameters, (A) LSV curves of various catalysts[41]. Copyright 2020, Springer Nature. (B) Tafel slope of catalysts[43]. Copyright 2016, Springer Nature. (C) Nyquist semicircle of catalyst[45]. Copyright 2021. American Chemical Society. (D) Stability of catalysts[47]. Copyright 2018, Springer Nature.
(1) Overpotential [Figure 3A]: In theory, for the HER, the required thermal dynamic potential is 1.23 V. To overcome the intrinsic activation barriers caused by the anode and cathode, an overpotential must be added[41]. The added overpotential of the catalysts is an important parameter for comparing their performance. The lower the overpotential, the better the catalytic material[42].
(2) Tafel slope [Figure 3B]: The Tafel slope could unveil the mechanism of the HER process; the lower the Tafel slope, the faster the electrocatalytic reaction kinetics[43]. This implied that catalysts with small Tafel slopes are desirable for HER applications[44].
(3) Conductivity [Figure 3C]: The conductivity of the catalysts is another crucial parameter for evaluating the efficiency of the catalyst activities[45]. The higher the conductivity of the catalysts, the easier the two-electron transfer. Therefore, hydrogen could be easily released[46].
(4) Stability [Figure 3D]: Catalyst stability is a key factor in evaluating the prospects of materials for commercial products[47]. High performance and superior stability of catalysts are the targets of research in the field of catalysis[48,49].
MoS2 CATALYSTS: STRUCTURE, PROPERTIES, AND HER PERFORMANCE
Structure and properties
MoS2 is a typical material with two-dimensional dichalcogenide (TMD) groups, which can be formed using MX2 (M = Transition metals; Ti, Zr, Hf, V, Nb, Ta, Mo, W, Tc, Re, Co, Rh, Ir, Ni, Pd, and Pt),
Figure 4. Structural features and properties of MoS2. (A) 3D structure[51]. Copyright 2011, Springer Nature. (B) Top view and side view of 2H and 1T MoS2[52]. Copyright 2017, American Chemical Society. (C) Lattice constant of MoS2[53]. Copyright 2016, Taylor & Francis. (D) Band structures of MoS2[59]. Copyright 2011, American Physical Society. (E) HER volcano plot of MoS2 and metal[61]. Copyright 2017, The American Association for the Advancement of Science.
Synthesis process and HER performance of catalysts based on MoS2
To prepare catalysts based on MoS2 materials, various techniques and processes have been developed to optimize the efficiency of those materials.
Exfoliation
Exfoliation is the most conventional technique for preparing effective materials for catalytic, electrochemical storage, and sensor applications. Using the exfoliation process, bulk MoS2 could be detached into a few layers, bilayers, or monolayers, which could exhibit a direct bandgap compared with the indirect bandgap of bulk MoS2[63-65]. Layered MoS2 is an ideal catalyst for electrochemical processes, such as the HER, because it can provide numerous active sites on the edge of the layers and the super intrinsic conductivity of the MoS2 layer[66,67]. Figure 5A presents the mechanism of the exfoliation process based on the MoS2 material using sonication in n-butyllithium for 1.5 h[68]. During sonication, lithium ions were intercalated into the bulk MoS2, and the layered MoS2 gradually detached to form a monolayer catalyst. The main advantages of this route include a simple process, low cost, and highly pure catalyst. However, several drawbacks limit the use of this method, such as time consumption, the danger of using lithium materials, and the restacking of exfoliated MoS2. Another major challenge was to effectively transfer the exfoliated MoS2 monolayer onto the surface of the cathode. This is because the catalyst coated on the electrode was unstable and nonuniform.
Chemical vapor deposition
To date, the chemical vapor deposition (CVD) process is preferred for the preparation of large-area and high-quality MoS2 layers that can be used for various applications[69-71]. Figure 5B shows the mechanism that could occur in a glass chamber at high temperatures[72]. Using this technique, the number of MoS2 layers can be controlled, which is beneficial for the HER. In the CVD process, there are several approaches for preparing MoS2 thin films, such as sulfurization of the deposited molybdenum or molybdenum oxide, vapor-solid growth based on MoS2 bulk materials, and sulfurization of coated thiomolybdate compounds. The main barriers to this technique are its complexity and high cost. Low product yield is another drawback of this technique.
Hydro/solvothermal process
To prepare catalytic materials, the hydro/solvothermal process is considered the most favorable strategy for synthesizing, doping, or even structure-engineering catalysts[73-75]. The source materials, after pretreatment, could be put into a Teflon-lined stainless-steel autoclave at a high temperature (150-300 °C) for a long reaction time (10-30 h). The structure and morphology of the catalysts can be easily prepared or modified by changing the synthesis conditions, such as the temperature, time, and ratio of raw materials. Using this method, heterostructures of various catalysts can be easily prepared. The main disadvantage of this process is the elemental content of the products, which could affect the properties of the synthesized materials. Figure 5C presents the mechanism of the hydro/solvothermal process for preparing MoS2 nanoflowers, which have been intensively investigated for HER with excellent catalytic activities[76].
HER performance of catalysts based on MoS2
Catalysts based on MoS2 show excellent performance in HER applications. Figure 6 shows the HER performance of various structures of MoS2 prepared by different processes. Figure 6A demonstrates the performance of MoS2 catalysts prepared by the exfoliation technique[77]. As can be seen, after the exfoliation process, the 2H form of MoS2 could be converted into 1T form which is metallic and more conductive compared with the initial form. Therefore, the catalytic activity of the material was drastically enhanced. The 1T MoS2 exhibits great performance with the electrocatalytic current density of 10 mA cm-2 at a low overpotential of -187 mV vs. the reversible hydrogen electrode (RHE) and a Tafel slope of 43 mV dec-1 while the performance of 2H MoS2 demonstrated the electrocatalytic current density of 10 mA cm-2 at an overpotential of -320 mV vs. RHE and a Tafel slope of 110 mV dec-1. This improvement can be attributed to the metallic MoS2 polymorph form, which exhibits facile electrode kinetics and low-loss electrical transport and possesses a proliferated density of catalytically active sites. Another route, the hydro/thermal solution process, has been intensively used to synthesize and/or modify different catalyst structures based on MoS2 materials.
As shown in Figure 6B, Van Nguyen et al. reported a unique process to synthesize and modify the MoS2 morphology by changing the pH and temperature; different morphologies of MoS2 were successfully prepared[78]. Among them, the small flower MoS2 with dimensions of less than 100 nm presented a significant improvement compared to that of the normal nanoflower MoS2 (900-1,500 nm). MoS2 small flowers exhibit superior electrocatalytic activity toward HER with a low Tafel slope of 49 mV dec-1 and an overpotential of 270 mV at a current density of 50 mA cm-2. In this case, the catalytic improvement can be attributed to the large surface area, which was caused by the uniformity and small size of the flower catalysts.
The most effective technique for preparing a MoS2-catalyst for the HER is the CVD process, as shown in Figure 6C. The CVD process can provide the most effective catalyst based on MoS2 because monolayer or bilayer MoS2 can be synthesized and/or modified. The super thin film MoS2 exhibits superior catalytic activity for two-dimensional materials such as MoS2. Xu et al. studied the performance of monolayer MoS2 for HER applications based on the Frekel defect: FD-MoS2[79]. At the current density of 10 mA cm-2, the optimal Frenkel-defected monolayer MoS2 exhibits a lower overpotential (164 mV) than either pristine monolayer MoS2 surface plane (358 mV) or Pt-single-atom doped MoS2 (211 mV). The FD-MoS2 presented a low Tafel slope (36 mV dec-1) which may be owing to the performance of Pt. The existence of Frenkel defects in MoS2 could lead to a unique charge distribution that changes the H adsorption sites and provides moderate H* adsorption energy for FD-MoS2.
MOF MATERIALS: PROCESS AND PROPERTIES
Synthesis process and properties
MOF materials are a class of ultrahigh-porosity materials that can be formed between metal ions bonded by organic ligand linkers[80,81]. MOF materials could provide up to 90% of the free volume with a large surface area, which could be extended to over 6,000 m2/g. The combination of organic and inorganic elements in super porous MOFs could be beneficial for many potential applications such as clean energy, hydrogen technology, and storage technology[82-86].
MOFs are porous materials made up of metal centers and organic ligands with infinite lattice structures that enhance their catalytic performance through various methods[87]. The specific surface area of MOFs enhances catalytic performance in HER processes due to their tailorable porous structures[88]. MOFs bridge the gap between mesoporous materials and microporous zeolites, offering highly controllable pore sizes and large surface areas that facilitate selective catalysis and enhance molecule adsorption. In addition, the porous structure of MOFs allows electrolytes to penetrate and reach inner active sites, thus accelerating catalytic performance. Furthermore, modulating the electronic structure of active sites, including spin ordering and energy band structures, further improves intrinsic electrocatalytic properties[89]. Techniques such as lattice strain engineering and pore partitioning further enhance catalytic efficiency by creating adaptive hetero-junctions and introducing novel heterometallic species. Moreover, embedding nanoparticles, such as Pt, Pd, or Ru, within MOFs introduces unique catalytic properties and synergistic effects, where the high surface area and stability of MOFs support the high catalytic activity of nanoparticles[90]. The uniform dispersion of nanoparticles within the MOF matrix prevents aggregation and ensures stable catalytic performance. Additionally, the tailored pore environments of MOFs can preferentially allow specific reactants to access the nanoparticles, enhancing selectivity, while facilitating electron transfer processes that improve reactivity.
The mechanism of the MOF process is shown in Figure 7A, in which the node-space arrangement is formed by organic linkers that can connect metal ions or clusters[91]. Therefore, synthesized materials present various advantages such as high porosity and large surface area, which could be beneficial for different technologies, particularly electrochemical processes.
To synthesize and/or engineer the structure of MOF, in recent decades, researchers have investigated and developed numerous MOF types using different techniques, which are briefly discussed below. The synthesis method of MOFs can significantly influence their specific surface area and catalytic properties, which are crucial for their applications in gas storage, separation, and catalysis. Different synthesis conditions, such as temperature, solvent, and reaction time, can be adjusted to control the pore size and surface area of MOFs. The catalytic properties of MOFs can also be post-synthetically modified by incorporating different metal ions or functional groups, to enhance their catalytic activity and performance[92,93].
Microwave-assisted methods
Microwave-assisted methods are usually employed with electromagnetic radiation (0.3-300 GHz). The advantages of microwave assistance include high yields, excellent control, and fast reaction times. Bu et al. reported the microwave-assisted synthesis of (FeNiP)/P-doped graphene[94]. In this study, various MOFs (phosphide/graphene composites with adjustable heterostructures, including transition metal
Electrochemical process
A thin film with controllable thickness based on MOF materials can be easily prepared using electrochemical techniques. The benefits of these routes are the high quality and homogeneity of thin-film materials. Alagar et al. developed a process for synthesizing CuZn-MOFs via controlled electrodeposition[95]. In this study, CuZ-BTC-250 (BTC = 1,3,5-benzenetricarboxylate) was successfully prepared, which shows a significant increase in HER application with the onset potential of 1.37 V, whereas the commercially available RuO2‖Pt/C exhibits 1.38 V in alkaline solutions during the overall water splitting.
Ultrasonic synthesis
This process can be performed using high energy unbound to a reaction mixture. The benefits of this process are its low cost, simplicity, and nonuse of toxic materials. Eliwa reported a process for producing a Pb-MOF catalyst via ultrasonication for 60-75 min. The synthesized catalyst was then investigated for HER application which showed good performance with the current density of 50 mA cm-2 at an overpotential of
Hydrothermal/solvothermal methods
The process could occur in closed systems, such as an autoclave, which could use different solvents at high temperatures (100-250 °C) and for a long time (10-30 h). This is the simplest, high-yield method for the preparation of MOF catalysts, which has been intensively investigated in previous studies[96-100]. Ma et al. reported a MOF-derived flower-like MoS2@TiO2 nanohybrid, which benefited the HER process, using a simple hydrothermal method[101]. Using this technique, the ratio of materials can be easily controlled. The authors concluded that at a ratio of 14.6% MoS2, the synthesized material could show the significant performance of HER with an onset overpotential of -300 mV (vs. RHE) and a Tafel slope of ~81 mV dec-1. The increased performance of the prepared catalyst could be attributed to the in-situ formation of active sites and uniform dispersion, as well as the strong connection between MoS2 and TiO2, which can facilitate electron transfer in the electrochemical process.
In general, as shown in Figure 7B, various types of MOFs have been synthesized and reported to apply to energy storage and saving[102]. The unit cells and frameworks of typical MOFs are shown in Figure 7C[103].
MOF materials for HER application
Owing to their many advantageous properties that could benefit electrochemical processes, such as high porosity and large surface areas, MOF materials have recently been extensively applied in the HER. As seen in Figure 8, the most effective way to utilize the benefits of MOF for HER applications is to dope highly catalytic metals, such as Ru and Pt, into the MOF framework. As shown in Figure 8A, the Ru-doped MOF material based on Cu-BTC forms Ru-Cu@C[104]. The optimized Ru-Cu@C-2 catalyst shows superior HER performance with an extremely low overpotential (20 mV at 10 mA cm-2), ultralow Tafel slope
MOF/MoS2 HETEROSTRUCTURE: SYNTHESIS PROCESS AND HER ACTIVITIES
Synthesis strategies of catalysts based on MOF/MoS2 materials
To exploit the advantages of both MoS2 and MOF materials, heterostructure materials based on MoS2 and MOF have been investigated. These hybrid catalysts show excellent catalytic activity toward HER applications. Therefore, different processes have been used to prepare these catalysts. There are two conventional processes for preparing heterostructure catalysts based on MOFs and MoS2, as illustrated in Figure 9. As shown in Figure 9A, The MOF/MoS2 catalyst was effectively synthesized in one step by CVD[106]. In addition, MOF and MoS2 materials can be separately synthesized using various techniques, and the synthesized MOF or MoS2 can be placed into the prepared solution to form a heterostructure of
HER activities of catalysts based on MOF/MoS2 materials
Catalysts based on MOF/MoS2 heterostructures show significant performance compared to other catalysts. As can be seen in Figure 10, for various heterostructures of MOF/MoS2 prepared by different routes, the performance of the synthesized heterostructures dramatically increased compared with that of the initial materials. The synthesis strategy used for formation of MoS2/MOF heterostructures significantly affects their properties and performance[108-110]. Hydrothermal/solvothermal methods yield high crystallinity heterostructures with strong interactions but require high temperatures and long reaction times. Mechanical exfoliation and mixing are simple and cost-effective but may result in weaker interactions and less uniform distribution. CVD provides high-purity, well-controlled MoS2 layers with excellent electronic properties but is complex and costly. Electrochemical deposition allows precise, uniform MoS2 coverage and is cost-effective, though it may need optimization for consistent quality. Thus, the choice of method depends on the desired properties, scalability, and application requirements.
Figure 10A shows the one-step process for synthesizing the heterostructure of a catalyst based on
As shown in Figure 10B and C, heterostructure catalysts based on MoS2/MOF were prepared by a multistep process. In these processes, MoS2 could be separately synthesized in the first step and then combined with MOF source materials to form heterostructure materials. The heterostructure catalysts MoS2 and MOF showed HER improvements similar to those of the pure MoS2 and MOF materials. The main reason for this is the benefits of both MOF and MoS2 and the synergistic effect between multiple elements in binary catalysts.
Strategies to increase HER performance of catalysts based on MoS2/MOF materials
The outstanding properties of MoS2 and MOF materials are discussed in detail. The performance improvement of MoS2/MOF materials arises from several synergistic mechanisms. First, the high surface area and tunable porosity of MOFs enhance the dispersion of MoS2, increasing the number of accessible active sites. This structural feature also facilitates efficient mass transport and diffusion of reactants to these active sites. Additionally, the electronic properties of MoS2, such as high conductivity and catalytic activity, complement the stability and structural support provided by the MOFs. Thus, the intimate contact between MoS2 and MOFs enhances electron transfer efficiency, reducing charge recombination and boosting overall catalytic performance[111]. The results indicated that the combination of the two materials could be used as a catalyst for HER applications. However, the performance of the prepared products remains quite different from that of practical materials. Therefore, several strategies can be adopted to improve the efficiency of catalysts based on MoS2/MOF materials. Various strategies have been studied to increase the catalytic activity of MOF/MoS2 materials [Figure 11]. Noble metal-Pt-doped MoS2/MOF is the most effective for increasing the performance of catalysts based on the excellent characteristics of Pt. In this study, Rong et al. prepared a rose-like structured CuSNC@MoS2-Pt electrocatalyst Figure 11A[112]. Thus, the performance of the synthesized materials was significantly improved. The results indicated that the synergistic effects of
Nonmetal doping is another potential strategy for improving the performance of catalysts. Various processes have been reported to improve catalytic activity by adding small amounts of P, N, or S. As shown in Figure 11B, the HER performance of the P-doped catalyst was significantly better than that of the undoped MoS2/MOF catalyst. The results indicated that the P-doped catalyst based on MoS2/MOF shows increased HER activity with a low overpotential of 84 mV compared to those of NiCoC-MOF,
Another effective technique that could be employed to improve the performance of catalysts based on
CONCLUSION AND PERSPECTIVE
Among several non-noble metal catalysts, MoS2 is the most popular and has been intensively investigated for different applications because of its unique structure and special properties. For HER applications, MoS2 is considered to be a prominent catalyst that could replace the Pt group in the electrochemical process because of its d-band electronic structure, analogous to that of noble metals. Many routes and techniques have been used to synthesize and enhance the performance of catalysts based on MoS2 to produce hydrogen gas. The application of catalysts based on MoS2 for the HER is still being conducted in the laboratory. Some barriers exist to the commercial preparation of hydrogen gas using these catalysts because of the low efficiency and/or stability of the desired performance of practical materials.
Emerging as a unique material, the MOF group exhibits high porosity and possesses a superlarge surface area. High porosity and a large surface area are critical points in the electrochemical process for releasing gases. Recently, MOF-based catalysts have been extensively investigated for HER applications. However, the main drawbacks of these catalysts are their low conductivities and poor stability in strong electrolytes. Therefore, increasing the conductivity and lifetime of MOF catalysts is a key challenge in the preparation of practical materials for hydrogen technologies. Various methods, including structural modification, nonmetal and/or metal-doped catalysts, and heterostructures with other materials, have been thoroughly investigated.
The integration of the two most promising materials, MoS2 and MOF, to prepare catalysts for the HER process is an outstanding strategy that utilizes the advantages of both materials. The stability and good catalytic activity of MoS2 and the highly porous and large active sites of the MOF materials are important for the synthesis of effective catalysts for hydrogen production. Catalysts based on the MoS2/MOF heterostructure present the benchmark HER performance and could be considered industrial-scale catalysts soon. However, some challenges need to be overcome, such as the conductivity and catalytic activities, which are still unworthy of practical application. Technological developments and various strategies, such as metal/nonmetal doping in heterostructure catalysts, could create a synergistic effect or increase the conductivity and improve the catalytic activities of MoS2/MOF catalysts. After clearing these barriers, there is no doubt that, soon, catalysts based on MoS2/MOF could play a crucial role as a promising technology for catalyst applications.
DECLARATIONS
Authors’ contributions
Conceptualization, investigation, writing - original draft: Van Nguyen T
Conceptualization, investigation, Writing: Tekalgne MA
Conceptualization: Van Le Q, Van Tran C
Supervision, writing - review & editing: Ahn SH
Project administration, supervision, writing - review & editing: Kim SY
Availability of data and materials
Not applicable.
Financial support and sponsorship
This research was supported by the National Research Foundation of Korea (NRF), which was funded by the Korean government (2022M3H4A1A01012712).
Conflict of Interest
All authors declared that there are no conflicts of interest.
Ethical approval and consent to participate
Not applicable.
Consent for publication
Not applicable.
Copyright
© The Author(s) 2024.
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Van, Nguyen T.; Tekalgne M.; Van Le Q.; Van Tran C.; Ahn S. H.; Kim S. Y. Recent progress and strategies of non-noble metal electrocatalysts based on MoS2/MOF for the hydrogen evolution reaction in water electrolysis: an overview. Microstructures. 2024, 4, 2024046. http://dx.doi.org/10.20517/microstructures.2024.24
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