| 1. |
- Li, Guowei, et al.
(författare)
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Carbon-Tailored Semimetal MoP as an Efficient Hydrogen Evolution Electrocatalyst in Both Alkaline and Acid Media
- 2018
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Ingår i: Advanced Energy Materials. - : WILEY-V C H VERLAG GMBH. - 1614-6832 .- 1614-6840. ; 8:24
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Tidskriftsartikel (refereegranskat)abstract
- The electrolysis processes such as hydrogen evolution reaction (HER) require high efficient catalysts with robust surface stability. A high conductivity is also necessary to speed up the charge transport between the catalyst and the electrolyte. Recently, the observation of exceedingly high conductivity in the topological semimetal MoP, has provided a model catalyst to investigate the correlation between the electrical transport and the electrocatalytic activity for the HER. Thus, MoP is encapsulated in a Mo, P codoped carbon layer (MoP@C). This composite material exhibits outstanding HER performance, with an extremely low overpotential of 49 mV at a current density of 10 mA cm(-2) and a Tafel slope of 54 mV dec(-1) in an alkaline medium. In addition, electron transport analysis indicates that MoP exhibits high conductivity and mobility due to the existence of triple-point fermions and a complex Fermi surface. Furthermore, the presence of P-C and Mo-C bonds at the interface between the carbon layer and the MoP particles modulates the band structure of MoP@C and facilitates fast electron transfer, accumulation, and subsequent delocalization, which are in turn responsible for the excellent HER activity.
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| 2. |
- Li, Guowei, et al.
(författare)
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Dirac Nodal Arc Semimetal PtSn4: An Ideal Platform for Understanding Surface Properties and Catalysis for Hydrogen Evolution
- 2019
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Ingår i: Angewandte Chemie International Edition. - : WILEY-V C H VERLAG GMBH. - 1433-7851 .- 1521-3773.
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Tidskriftsartikel (refereegranskat)abstract
- Conductivity, carrier mobility, and a suitable Gibbs free energy are important criteria that determine the performance of catalysts for a hydrogen evolution reaction (HER). However, it is a challenge to combine these factors into a single compound. Herein, we discover a superior electrocatalyst for a HER in the recently identified Dirac nodal arc semimetal PtSn4. The determined turnover frequency (TOF) for each active site of PtSn4 is 1.54 H-2 s(-1) at 100 mV. This sets a benchmark for HER catalysis on Pt-based noble metals and earth-abundant metal catalysts. We make use of the robust surface states of PtSn4 as their electrons can be transferred to the adsorbed hydrogen atoms in the catalytic process more efficiently. In addition, PtSn4 displays excellent chemical and electrochemical stabilities after long-term exposure in air and long-time HER stability tests.
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| 3. |
- Li, Guowei, et al.
(författare)
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Synergistically creating sulfur vacancies in semimetal-supported amorphous MoS2 for efficient hydrogen evolution
- 2019
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Ingår i: Applied Catalysis B. - : Elsevier. - 0926-3373 .- 1873-3883. ; 254
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Tidskriftsartikel (refereegranskat)abstract
- The presence of elemental vacancies in materials are inevitable according to statistical thermodynamics, which will decide the chemical and physical properties of the investigated system. However, the controlled manipulation of vacancies for specific applications is a challenge. Here we report a facile method for creating large concentrations of S vacancies in the inert basal plane of MoS2 supported on semimetal CoMoP2. With a small applied potential, S atoms can be removed in the form of H2S due to the optimized free energy of formation. The existence of vacancies favors electron injection from the electrode to the active site by decreasing the contact resistance. As a consequence, the catalytic current is increased by 221% with the vacancy-rich MoS2 as electrocatalyst for hydrogen evolution reaction (HER). A small overpotential of 75 mV is needed to deliver a current density of 10 mA cm(-2), which is considered among the best values achieved for MoS2. It is envisaged that this work may provide a new strategy for utilizing the semimetal phase for structuring MoS2 into a multi-functional material.
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| 4. |
- Vennström, Marie
(författare)
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Crystal Chemistry of the Ti3Sn-D, Nb4MSi-D and Pd-Ni-P Systems
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Future energy systems based on hydrogen as energy carrier require reliable ways for storing hydrogen gas in safe, clean and efficient ways. Metal hydrides absorb hydrogen gas reversibly, making them suitable for storage applications. Investigations of the crystal structures of these materials contribute to an understanding of the factors which can influence the absorption. Three systems, Ti3Sn-D, Nb4MSi-D (M=Co or Ni) and Pd-Ni-P, have been investigated in this thesis. Various solid state synthesis techniques have been used for sample preparation. The crystal structures have been studied using x-ray and neutron diffraction techniques. Three metal hydride phases were found in the Ti3Sn-D system upon hydrogenation. Deuterium occupies titanium octahedra and the applied deuterium pressure induces the phase transitions. The distances between the deuterium atoms increase from 2.47 Å in orthorhombic Ti3SnD0.80 to 4.17 Å in cubic Ti3SnD. The Nb4MSi-D system (M=Co or Ni) readily absorbs deuterium at room temperature and 90 kPa deuterium pressure to give a deuterium content of Nb4MSiD~2.5. Two interstitial voids, both coordinated by four niobium atoms arranged in a tetrahedral configuration, accommodate deuterium atoms. Two ternary phases and a solid solution of nickel in Pd3P have been synthesised and the crystal structures determined. PdNi2P is orthorhombic and crystallises in the MgCuAl2-type structure: an ordered derivative of the Re3B-type structure. Pd8Ni31P16 is a tetragonal high-temperature phase stable at 700°C with 110 atoms in the unit cell. Pd2.7Ni0.3P0.94 has the cementite-type structure with mixed occupancy of palladium and nickel at one of the two non-equivalent crystallographic metal positions.
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