Plasma functionalization can increase the efficiency of MoSe2 in the hydrogen evolution reaction (HER) by providing multiple species but the interactions between the plasma and catalyst are not well understood. In this work, the effects of the ion energy and plasma density on the catalytic properties of MoSe2 nanosheets are studied. The through‐holes resulting from plasma etching and multi‐vacancies induced by plasma‐induced damage enhance the HER efficiency as exemplified by a small overpotential of 148 mV at 10 mA cm–2 and Tafel slope of 51.6 mV dec–1 after the plasma treatment using a power of 20 W. The interactions between the plasma and catalyst during etching and vacancies generation are evaluated by plasma simulation. Finite element and first‐principles density functional theory calculations are also conducted and the results are consistent with the experimental results, indicating that the improved HER catalytic activity stems from the enhanced electric field and more active sites on the catalyst, and reduced bandgap and adsorption energy arising from the etched through‐holes and vacancies, respectively. The results convey new fundamental knowledge about the plasma effects and means to enhance the efficiency of catalysts in water splitting as well insights into the design of high‐performance HER catalysts.
In bone implants, antibacterial biomaterials with nonleaching surfaces are superior to ones based on abrupt release because systemic side effects arising from the latter can be avoided. In this work, a nonleaching antibacterial concept is demonstrated by fabricating 2D nanoflakes in situ on magnesium (Mg). Different from the conventional antibacterial mechanisms that depend on Mg2+ release and pH increase, the nanoflakes exert mechanical tension onto the bacteria membranes to destroy microorganisms on contact and produce intracellular stress via physical interactions, which is also revealed by computational simulations. Moreover, the nanoflake layer decelerates the corrosion process resulting in mitigated Mg2+ release, weaker alkalinity in the vicinity, and less hydrogen evolution, in turn inducing less inflammatory reactions and ensuring the biocompatibility as confirmed by the in vivo study. In this way, bacteria are killed by a mechanical process causing very little side effects. This work provides information and insights pertaining to the design of multifunctional biomaterials.
MoSe 2 is an efficient catalyst for the hydrogen evolution reaction (HER) and can potentially replace conventional catalysts composed of noble metals such as Pt. The HER activity of MoSe 2 originates mainly from the edge sites of Se atoms, but the low concentration of Se exposed to the electrolyte hampers the performance. Hence, activating a larger portion of the basal plane of Se atoms is an effective way to improve the HER properties. Herein, a 3D hierarchic nanoflower structure comprising MoSe 2 with atomic-scale interlayered graphene layers in the nanosheets is designed and prepared to improve the electron conductivity and decrease the proportions of inactive basal planes. Raman scattering, transmission electron microscopy, and energy-dispersive X-ray spectroscopy verify effective insertion of graphene layers in MoSe 2 , and the HER characteristics are improved as exemplified by a small overpotential of 175 mV at 10 mA cm −2 , small Tafel slope of 58 mV dec −1 , and excellent durability with only small deterioration of 10 mV after 10,000 cycles. First-principles density functional theory and finite element method calculations corroborate the experimental results, revealing better conductivity and hydrogen adsorption/desorption ability rendered by the graphene layers. Our results reveal a new and effective strategy to optimize the structure and composition and reduce the hydrogen adsorption energy barrier in the pursuit of high-efficiency non-noble metal catalysts.
The response of immune systems is crucial to the success of biomedical implants in vivo and in particular, orthopedic implants must possess proper immunomodulatory functions to allow sufficient osteointegration. In...
Inexpensive and efficient catalysts are crucial to industrial adoption of the electrochemical hydrogen evolution reaction (HER) to produce hydrogen. Although two‐dimensional (2D) MoS2 materials have large specific surface areas, the catalytic efficiency is normally low. In this work, Ag and other dopants are plasma‐implanted into MoS2 to tailor the surface and interface to enhance the HER activity. The HER activty increases initially and then decreases with increasing dopant concentrations and implantation of Ag is observed to produce better results than Ti, Zr, Cr, N, and C. At a current density of 400 mA cm−2, the overpotential of Ag500‐MoS2@Ni3S2/NF is 150 mV and the Tafel slope is 41.7 mV dec−1. First‐principles calculation and experimental results reveal that Ag has higher hydrogen adsorption activity than the other dopants and the recovered S sites on the basal plane caused by plasma doping facilitate water splitting. In the two‐electrode overall water splitting system with Ag500‐MoS2@Ni3S2/NF, a small cell voltage of 1.47 V yields 10 mA cm−2 and very little degradation is observed after operation for 70 hours. The results reveal a flexible and controllable strategy to optimize the surface and interface of MoS2 boding well for hydrogen production by commercial water splitting.
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