| 1. |
- Najafi, Leyla, et al.
(author)
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Microwave-Induced Structural Engineering and Pt Trapping in 6R-TaS2 for the Hydrogen Evolution Reaction
- 2020
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In: Small. - : Wiley. - 1613-6810 .- 1613-6829. ; 16:50
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Journal article (peer-reviewed)abstract
- The nanoengineering of the structure of transition metal dichalcogenides (TMDs) is widely pursued to develop viable catalysts for the hydrogen evolution reaction (HER) alternative to the precious metallic ones. Metallic group-5 TMDs have been demonstrated to be effective catalysts for the HER in acidic media, making affordable real proton exchange membrane water electrolysers. Their key-plus relies on the fact that both their basal planes and edges are catalytically active for the HER. In this work, the 6R phase of TaS2 is "rediscovered" and engineered. A liquid-phase microwave treatment is used to modify the structural properties of the 6R-TaS2 nanoflakes produced by liquid-phase exfoliation. The fragmentation of the nanoflakes and their evolution from monocrystalline to partly polycrystalline structures improve the HER-activity, lowering the overpotential at cathodic current of 10 mA cm(-2) from 0.377 to 0.119 V. Furthermore, 6R-TaS2 nanoflakes act as ideal support to firmly trap Pt species, which achieve a mass activity (MA) up 10 000 A g(Pt)(-1) at overpotential of 50 mV (20 000 A g(Pt)(-1) at overpotentials of 72 mV), representing a 20-fold increase of the MA of Pt measured for the Pt/C reference, and approaching the state-of-the-art of the Pt mass activity.
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| 2. |
- Palei, Milan, et al.
(author)
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Photoluminescence enhancement and high accuracy patterning of lead halide perovskite single crystals by MeV ion beam irradiation
- 2020
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In: Journal of Materials Chemistry C. - : Royal Society of Chemistry (RSC). - 2050-7526 .- 2050-7534. ; 8:29, s. 9923-9930
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Journal article (peer-reviewed)abstract
- Focused ion beam (FIB) has recently been used to tune the optical properties of lead halide perovskites (LHPs), opening an interesting avenue for applications in optoelectronic devices. However, it has remained an open question to date whether FIB can be used to locally enhance the photoluminescence (PL) of LHPs. In this work we irradiate MAPbBr(3)(MA = methylammonium) single crystals with a high energy micron-sized ion probe of different ionic masses (3 MeV He+, 12.5 MeV Br5+, and 20 MeV I7+) and study the PL as a function of the damage induced by the ion beam. We find that at low damage levels the PL is enhanced about six times with respect to the pristine material, while increasing the damage level produces a progressive PL decrease, and, above a threshold, the PL is finally quenched below the value of the pristine crystal. We attribute this behavior to the interaction of free carriers with irradiation induced surface defects: at low damage levels the migration of carriers toward the bulk is inhibitedviatrapping-detrapping events at surface defects, allowing their radiative recombination near the surface; at higher damage, though, the probability for non-radiative recombination increases and gradually becomes dominant. We thus present a method to locally increase the PL of bulk LHP, which could be applied in a wide range of fields, such as highly sensitive ion beam detection or future optoelectronic device design.
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