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Hierarchical Ni-Mo-S nanosheets on carbon fiber cloth: A flexible electrode for efficient hydrogen generation in neutral electrolyte.

Miao J, Xiao FX, Yang HB, Khoo SY, Chen J, Fan Z, Hsu YY, Chen HM, Zhang H, Liu B - Sci Adv (2015)

Bottom Line: The incorporation of Ni atoms in Mo-S plays a crucial role in tuning its intrinsic catalytic property by creating substantial defect sites as well as modifying the morphology of Ni-Mo-S network at atomic scale, resulting in an impressive enhancement in the catalytic activity.Furthermore, the Ni-Mo-S/C electrode has excellent electrocatalytic stability over an extended period, much better than those of MoS2/C and Pt plate electrodes.The intuitive comparison test was designed to reveal the superior gas-evolving profile of Ni-Mo-S/C over that of MoS2/C, and a laboratory-scale hydrogen generator was further assembled to demonstrate its potential application in practical appliances.

View Article: PubMed Central - PubMed

Affiliation: School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore 637459, Singapore.

ABSTRACT
A unique functional electrode made of hierarchal Ni-Mo-S nanosheets with abundant exposed edges anchored on conductive and flexible carbon fiber cloth, referred to as Ni-Mo-S/C, has been developed through a facile biomolecule-assisted hydrothermal method. The incorporation of Ni atoms in Mo-S plays a crucial role in tuning its intrinsic catalytic property by creating substantial defect sites as well as modifying the morphology of Ni-Mo-S network at atomic scale, resulting in an impressive enhancement in the catalytic activity. The Ni-Mo-S/C electrode exhibits a large cathodic current and a low onset potential for hydrogen evolution reaction in neutral electrolyte (pH ~7), for example, current density of 10 mA/cm(2) at a very small overpotential of 200 mV. Furthermore, the Ni-Mo-S/C electrode has excellent electrocatalytic stability over an extended period, much better than those of MoS2/C and Pt plate electrodes. Scanning and transmission electron microscopy, Raman spectroscopy, x-ray diffraction, x-ray photoelectron spectroscopy, and x-ray absorption spectroscopy were used to understand the formation process and electrocatalytic properties of Ni-Mo-S/C. The intuitive comparison test was designed to reveal the superior gas-evolving profile of Ni-Mo-S/C over that of MoS2/C, and a laboratory-scale hydrogen generator was further assembled to demonstrate its potential application in practical appliances.

No MeSH data available.


High-magnification SEM images.(A) Ni-Mo-S/C (3:1). (B) Ni-Mo-S/C (1:1). (C) Ni-Mo-S/C (1:3). (D) MoS2/C. All scale bars, 500 nm.
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Figure 3: High-magnification SEM images.(A) Ni-Mo-S/C (3:1). (B) Ni-Mo-S/C (1:1). (C) Ni-Mo-S/C (1:3). (D) MoS2/C. All scale bars, 500 nm.

Mentions: To gain more detailed insights into the morphological evolution, we further compared the high-magnification SEM images of different Ni-Mo-S/C samples. Figure 3A reveals that the nanostructured film in Ni-Mo-S/C (3:1) is composed of numerous nanosheets and large aggregated nanoparticles, which tightly stack onto the surface of carbon fibers. When the Ni-to-Mo ratio in the precursor solution is reduced to 1:1, a uniform nanostructured film composed of abundant edge-exposing nanosheets with an average thickness of 8 to 10 nm is formed, which develops into a nanoscale 3D network (Fig. 3B). The 3D nanostructure of Ni-Mo-S/C (1:1) is expected to benefit its HER application (22). Further increase in the Mo content in the growth solution (Ni/Mo, 1:3) results in the formation of bulky aggregates, which significantly decreases the density of exposed edge structures (Fig. 3C). If no Ni2+ is introduced into the synthesis, freely grown MoS2 can easily form large aggregates, which folded together and resembled the morphology of crumpled paper balls (Fig. 3D). The average thickness of MoS2 nanosheets is about 20 to 30 nm, which is about three times thicker than the edges in Ni-Mo-S (1:1) (Fig. 3B). The morphologies of different aggregates in different samples were compared (see fig. S5). It was found that the aggregates in MoS2/C, Ni-Mo-S/C (1:3), and Ni-Mo-S/C (1:1) are morphologically similar, and are all evolved from crumpled 2D-layered structures. In contrast, although the aggregates in Ni-Mo-S/C (3:1) and NiSx are similar in appearance, both of the aggregates are formed from nanoparticles. Obviously, the introduction of Ni2+ during the synthesis plays important roles in regulating the development of Ni-Mo-S nanostructures. The added Ni2+ may suppress the MoS2 crystal growth along the basal planes, thus lowering the probability of formation of stack-ups and coalescences among the nanosheets. However, overwhelming Ni2+ will prevent the formation of preferable 3D nanostructures on carbon fibers. Therefore, the optimized Ni-to-Mo precursor ratio in our synthesis is 1:1.


Hierarchical Ni-Mo-S nanosheets on carbon fiber cloth: A flexible electrode for efficient hydrogen generation in neutral electrolyte.

Miao J, Xiao FX, Yang HB, Khoo SY, Chen J, Fan Z, Hsu YY, Chen HM, Zhang H, Liu B - Sci Adv (2015)

High-magnification SEM images.(A) Ni-Mo-S/C (3:1). (B) Ni-Mo-S/C (1:1). (C) Ni-Mo-S/C (1:3). (D) MoS2/C. All scale bars, 500 nm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4643797&req=5

Figure 3: High-magnification SEM images.(A) Ni-Mo-S/C (3:1). (B) Ni-Mo-S/C (1:1). (C) Ni-Mo-S/C (1:3). (D) MoS2/C. All scale bars, 500 nm.
Mentions: To gain more detailed insights into the morphological evolution, we further compared the high-magnification SEM images of different Ni-Mo-S/C samples. Figure 3A reveals that the nanostructured film in Ni-Mo-S/C (3:1) is composed of numerous nanosheets and large aggregated nanoparticles, which tightly stack onto the surface of carbon fibers. When the Ni-to-Mo ratio in the precursor solution is reduced to 1:1, a uniform nanostructured film composed of abundant edge-exposing nanosheets with an average thickness of 8 to 10 nm is formed, which develops into a nanoscale 3D network (Fig. 3B). The 3D nanostructure of Ni-Mo-S/C (1:1) is expected to benefit its HER application (22). Further increase in the Mo content in the growth solution (Ni/Mo, 1:3) results in the formation of bulky aggregates, which significantly decreases the density of exposed edge structures (Fig. 3C). If no Ni2+ is introduced into the synthesis, freely grown MoS2 can easily form large aggregates, which folded together and resembled the morphology of crumpled paper balls (Fig. 3D). The average thickness of MoS2 nanosheets is about 20 to 30 nm, which is about three times thicker than the edges in Ni-Mo-S (1:1) (Fig. 3B). The morphologies of different aggregates in different samples were compared (see fig. S5). It was found that the aggregates in MoS2/C, Ni-Mo-S/C (1:3), and Ni-Mo-S/C (1:1) are morphologically similar, and are all evolved from crumpled 2D-layered structures. In contrast, although the aggregates in Ni-Mo-S/C (3:1) and NiSx are similar in appearance, both of the aggregates are formed from nanoparticles. Obviously, the introduction of Ni2+ during the synthesis plays important roles in regulating the development of Ni-Mo-S nanostructures. The added Ni2+ may suppress the MoS2 crystal growth along the basal planes, thus lowering the probability of formation of stack-ups and coalescences among the nanosheets. However, overwhelming Ni2+ will prevent the formation of preferable 3D nanostructures on carbon fibers. Therefore, the optimized Ni-to-Mo precursor ratio in our synthesis is 1:1.

Bottom Line: The incorporation of Ni atoms in Mo-S plays a crucial role in tuning its intrinsic catalytic property by creating substantial defect sites as well as modifying the morphology of Ni-Mo-S network at atomic scale, resulting in an impressive enhancement in the catalytic activity.Furthermore, the Ni-Mo-S/C electrode has excellent electrocatalytic stability over an extended period, much better than those of MoS2/C and Pt plate electrodes.The intuitive comparison test was designed to reveal the superior gas-evolving profile of Ni-Mo-S/C over that of MoS2/C, and a laboratory-scale hydrogen generator was further assembled to demonstrate its potential application in practical appliances.

View Article: PubMed Central - PubMed

Affiliation: School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore 637459, Singapore.

ABSTRACT
A unique functional electrode made of hierarchal Ni-Mo-S nanosheets with abundant exposed edges anchored on conductive and flexible carbon fiber cloth, referred to as Ni-Mo-S/C, has been developed through a facile biomolecule-assisted hydrothermal method. The incorporation of Ni atoms in Mo-S plays a crucial role in tuning its intrinsic catalytic property by creating substantial defect sites as well as modifying the morphology of Ni-Mo-S network at atomic scale, resulting in an impressive enhancement in the catalytic activity. The Ni-Mo-S/C electrode exhibits a large cathodic current and a low onset potential for hydrogen evolution reaction in neutral electrolyte (pH ~7), for example, current density of 10 mA/cm(2) at a very small overpotential of 200 mV. Furthermore, the Ni-Mo-S/C electrode has excellent electrocatalytic stability over an extended period, much better than those of MoS2/C and Pt plate electrodes. Scanning and transmission electron microscopy, Raman spectroscopy, x-ray diffraction, x-ray photoelectron spectroscopy, and x-ray absorption spectroscopy were used to understand the formation process and electrocatalytic properties of Ni-Mo-S/C. The intuitive comparison test was designed to reveal the superior gas-evolving profile of Ni-Mo-S/C over that of MoS2/C, and a laboratory-scale hydrogen generator was further assembled to demonstrate its potential application in practical appliances.

No MeSH data available.