Hydrothermally Synthesized MoS2 Nanoclusters for Hydrogen Evolution Reaction (original) (raw)
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Hydrothermal synthesis of 2D MoS2 nanosheets for electrocatalytic hydrogen evolution reaction
Nanostructured molybdenum disulfide (MoS2) is a very promising catalyst for producing molecular hydrogen by electrochemical methods. Herein, we have designed and synthesized highly electocatalytically active 2D MoS2 nanosheets (NS) from molybdenum trioxide (MoO3) by a facile hydrothermal method and have compared their electrocatalytic activities for hydrogen evolution reaction (HER). The electrochemical characterization was performed using linear sweep voltammetry (LSV) in acidic medium. The MoS2 NS show a HER onset potential at about 80 mV vs. reversible hydrogen electrode (RHE) which is much lower than MoO3 (300 mV). The MoS2 NS and MoO3 show a current density of 25 mA cm2 and 0.3 mA cm2, respectively at an overpotential of 280 mV vs. RHE. The MoS2 NS showed an 83 times higher current density when compared to MoO3. The Tafel slopes of the MoS2 NS and MoO3 were about 90 mV per dec and 110 mV per dec respectively. This suggests that MoS2 NS are a better electrocatalyst when compared to MoO3 and follow the Volmer–Heyrovsky mechanism for HER.
Conducting MoS2 Nanosheets as Catalysts for Hydrogen Evolution Reaction
Nano Letters, 2013
We report chemically exfoliated MoS 2 nanosheets with a very high concentration of metallic 1T phase using a solvent free intercalation method. After removing the excess of negative charges from the surface of the nanosheets, highly conducting 1T phase MoS 2 nanosheets exhibit excellent catalytic activity toward the evolution of hydrogen with a notably low Tafel slope of 40 mV/dec. By partially oxidizing MoS 2 , we found that the activity of 2H MoS 2 is significantly reduced after oxidation, consistent with edge oxidation. On the other hand, 1T MoS 2 remains unaffected after oxidation, suggesting that edges of the nanosheets are not the main active sites. The importance of electrical conductivity of the two phases on the hydrogen evolution reaction activity has been further confirmed by using carbon nanotubes to increase the conductivity of 2H MoS 2 .
High-performance hydrogen evolution electrocatalysis by layer-controlled MoS2 nanosheets
RSC Advances
Hydrogen is considered as an important clean energy carrier for the energy future and electrocatalytic splitting of water is one of the most efficient technologies for hydrogen production. As one potential alternative to Pt-based catalysts in hydrogen evolution reaction (HER), two-dimensional (2D) molybdenum sulfide (MoS2) nanomaterials have evoked enormous research interest while it remains a great challenge in the structure control for high-performance HER electrocatalysis due to the lack of efficient preparation techniques. Herein, we reported a one-pot chemical method to directly synthesize 2D MoS2 with controllable layers. Multiply-layer MoS2 (ML-MoS2), few-layer MoS2 (FL-MoS2) and single-layer MoS2 coating on carbon nanotubes (SL-MoS2-CNTs) can be efficiently prepared through the modulation of experimental conditions. The enhanced catalytic activity is demonstrated in HER with the layer number of MoS2 nanosheets reducing. Remarkably, the optimized SL-MoS2-CNTs sample showed lo...
ACS applied materials & interfaces, 2015
Molybdenum disulfide (MoS2) is a promising catalyst for hydrogen evolution reaction (HER) because of its unique nature to supply active sites in the reaction. However, the low density of active sites and their poor electrical conductivity have limited the performance of MoS2 in HER. In this work, we synthesized MoS2 nanosheets on three-dimensional (3D) conductive MoO2 via a two-step chemical vapor deposition (CVD) reaction. The 3D MoO2 structure can create structural disorders in MoS2 nanosheets (referred to as 3D MoS2/MoO2), which are responsible for providing the superior HER activity by exposing tremendous active sites of terminal disulfur of (in MoS2) as well as the backbone conductive oxide layer (of MoO2) to facilitate an interfacial charge transport for the proton reduction. In addition, the MoS2 nanosheets could protect the inner MoO2 core from the acidic electrolyte in the HER. The high activity of the as-synthesized 3D MoS2/MoO2 hybrid material in HER is attributed to the ...
ACS Omega, 2018
The design and fabrication of inexpensive highly efficient electrocatalysts for the production of hydrogen via the hydrogen evolution reaction (HER) underpin a plethora of emerging clean energy technologies. Herein, we report the fabrication of highly efficient electrocatalysts for the HER based on magnetron-sputtered MoS 2 onto a nanocarbon support, termed MoS 2 /C. Magnetron sputtering time is explored as a function of its physiochemical composition and HER performance; increased sputtering times give rise to materials with differing compositions, i.e., Mo 4+ to Mo 6+ and associated S anions (sulfide, elemental, and sulfate), and improved HER outputs. An optimized sputtering time of 45 min was used to fabricate the MoS 2 /C material. This gave rise to an optimal HER performance with regard to its HER onset potential, achievable current, and Tafel value, which were −0.44 (vs saturated calomel electrode (SCE)), −1.45 mV s −1 , and 43 mV dec −1 , respectively, which has the highest composition of Mo 4+ and sulfide (MoS 2). Electrochemical testing toward the HER via drop casting MoS 2 /C upon screen-printed electrodes (SPEs) to electrically wire the nanomaterial is found to be mass coverage dependent, where the current density increases up to a critical mass (ca. 50 μg cm −2), after which a plateau is observed. To allow for a translation of the bespoke fabricated MoS 2 /C from laboratory to new industrial applications, MoS 2 /C was incorporated into the bulk ink utilized in the fabrication of SPEs (denoted as MoS 2 /C-SPE), thus allowing for improved electrical wiring to the MoS 2 /C and resulting in the production of scalable and reproducible electrocatalytic platforms. The MoS 2 /C-SPEs displayed far greater HER catalysis with a 450 mV reduction in the HER onset potential and a 1.70 mA cm −2 increase in the achievable current density (recorded at −0.75 V (vs SCE)), compared to a bare/unmodified graphitic SPE. The approach of using magnetron sputtering to modify carbon with MoS 2 facilitates the production of mass-producible, stable, and effective electrode materials for possible use in electrolyzers, which are cost competitive to Pt and mitigate the need to use timeconsuming and low-yield exfoliation techniques typically used to fabricate pristine MoS 2 .
Efficient Electrocatalytic Hydrogen Evolution from MoS2-Functionalized Mo2N Nanostructures
ACS Applied Materials & Interfaces, 2017
Molybdenum-based compounds and their composites were investigated as an alternative to Pt for hydrogen evolution reactions. The presence of interfaces and junctions between Mo 2 N and MoS 2 grains in the composites were investigated to understand their role in electrochemical processes. Here we found that the electrocatalytic activity of Mo 2 N nanostructures was enhanced remarkably by conjugation with few-layer MoS 2 sheets. The electrocatalytic performance of Mo 2 N−MoS 2 composites in the hydrogen evolution reaction (HER) was revealed from the high catalytic current density of ∼175 mA cm −2 (at 400 mV) and good electrochemical stability (more than 18 h) in acidic media. Increasing the amount of MoS 2 in the composite, decreases the HER activity. The mechanism and kinetics of the HER process on the Mo 2 N−MoS 2 surface were analyzed using Tafel slopes and charge transfer resistance.
Chemistry of Materials, 2016
Herein, we report a unique thermal synthesis method to prepare a novel two-dimensional (2D) hybrid nanostructure consisted of ultrathin and tiny-sized molybdenum disulfide nanoplatelets homogenously inlaid in graphene sheets (MoS /G) with excellent electrocatalytic performance for HER. In this process, molybdenum oleate served as the source of both molybdenum and carbon, while crystalline sodium sulfate (Na 2 SO 4) served as both reaction template and sulfur source. The remarkable integration of MoS 2 and graphene in well-assembled 2D hybrid architecture provided large electrochemically active surface area and a huge number of active sites and also exhibited extraordinary collective properties for electron transport and H + trapping. The MoS 2 /G inlaid nanosheets deliver ultrahigh catalytic activity towards HER among the existing electrocatalysts with similar compositions, presenting a low onset overpotential approaching 30 mV, a current density of 10 mA/cm 2 at ~110 mV, and a Tafel slope as small as 67.4 mV/dec. Moreover, the strong bonding between MoS 2 nanoplatelets and graphene enabled outstanding long-term electrochemical stability and structural integrity, exhibiting almost 100% activity retention after 1,000 cycles and ~97% after 100,000 seconds of continuous testing (under static overpotential of-0.15 V). The synthetic strategy is simple, inexpensive and scalable for large-scale production, and also can be extended to diverse inlaid 2D nano-architectures with great potential for many other applications.
C, 2017
Hydrogen is an efficient fuel which can be generated via water splitting, however hydrogen evolution occurs at high overpotential, and efficient hydrogen evolution catalysts are desired to replace state-of-the-art catalysts such as platinum. Here, we report an advanced electrocatalyst that has low overpotential, efficient charge transfers kinetics, low Tafel slope and durable. Carbon nanofibers (CNFs), obtained by carbonizing electrospun fibers, were decorated with MoS 2 using a facile hydrothermal method. The imaging of catalyst reveals a flower like morphology that allows for exposure of edge sulfur sites to maximize the HER process. HER activity of MoS 2 decorated over CNFs was compared with MoS 2 without CNFs and with commercial MoS 2. MoS 2 grown over CNFs and MoS 2-synthesized produced about 374 and 98 times higher current density at −0.30 V (vs. Reversible Hydrogen Electrode, RHE) compared with the MoS 2-commercial sample, respectively. MoS 2-commercial, MoS 2-synthesized and MoS 2 grown over CNFs showed a Tafel slope of 165, 79 and 60 mV/decade, capacitance of 0.99, 5.87 and 15.66 mF/cm 2 , and turnover frequency of 0.013, 0.025 and 0.54 s −1 , respectively. The enhanced performance of MoS 2-CNFs is due to large electroactive surface area, more exposure of edge sulfur to the electrolyte, and easy charge transfer from MoS 2 to the electrode through conducting CNFs.
ChemistrySelect, 2017
MoS 2 nanospheres were formed using a template free hydrothermal process, which exhibit high catalytic activity towards hydrogen evolution reaction (HER). The extend of defect sites are probed by extended X-ray absorption fine structure which found decrease in coordination number at Mo site rather than at S site. DFT calculations identified an uneven strain and defect distribution between two S planes of curved MoS 2. Based on hydrogen adsorption on various sites, we identify a new pathway called "extended activity @ shielded defects", for Volmer-Tafel and Volmer-Heyrovsky mechanisms, where H adsorption occurs at exposed S layer driven by defects in underneath S layer of nanosphere. Having higher defect concentration it exhibited excellent HER activity with overpotential of À0.12 V, Tafel slope of 90 mV/decade, and higher turnover frequency. Our findings provide an avenue to design and engineer advanced nanostructures for catalysis, electronic devices, and other potential applications.