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Abstract Abundant transition metal borides are emerging as substitute electrochemical hydrogen evolution reaction (HER) catalysts for noble metals. Herein, an unusual canonic‐like behavior of theclattice parameter in the AlB2‐type solid solution Cr1–xMoxB2(x= 0, 0.25, 0.4, 0.5, 0.6, 0.75, 1) and its direct correlation to the HER activity in 0.5 M H2SO4solution are reported. The activity increases with increasingx, reaching its maximum atx= 0.6 before decreasing again. At high current densities, Cr0.4Mo0.6B2outperforms Pt/C, as it needs 180 mV less overpotential to drive an 800 mA cm−2current density. Cr0.4Mo0.6B2has excellent long‐term stability and durability showing no significant activity loss after 5000 cycles and 25 h of operation in acid. First‐principles calculations have correctly reproduced the nonlinear dependence of theclattice parameter and have shown that the mixed metal/B layers, such as (110), promote hydrogen evolution more efficiently forx= 0.6, supporting the experimental results.
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Ferrimagnetism and Half-metallicity in Cr-substituted Mn 4–x Cr x Al 11
Abstract Single crystals of disordered Mn4–xCrxAl11have been synthesized via the flux method. EDS on several crystals of various sizes and shapes revealed an average molar ratio of 17:9:74 for Mn:Cr:Al, while X-ray diffraction on three different crystals yield compositions Mn2.26Cr1.74Al11(Mn4–xCrxAl11,x= 1.74), Mn0.83Cr3.17Al11, and Mn1.07Cr2.93Al11. This compound crystallizes in space groupP–1, isostructural with both Mn4Al11and Cr4Al11. Magnetic measurements on several crystals show that this disordered compound is ferrimagnetic with a low effective moment ofμeff≈1.012±0.004 μB/f.u. and a non-reachable transition temperature. DFT calculations display opening of a bandgap in the spin-up channel near the Fermi level with increasing Cr content, an indication of half-metallicity.
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- PAR ID:
- 10590476
- Publisher / Repository:
- IOP Publishing
- Date Published:
- Journal Name:
- Journal of Physics: Condensed Matter
- ISSN:
- 0953-8984
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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