Synthesis and reaction sintering of WB

Matsudaira, Tsuneaki; Itoh, Hideaki; Naka, Shigeharu; Hamamoto, Hiroshi; Obayashi, Mikio

doi:10.1016/0267-3762(87)90114-7

Cited by 1 publication

(2 citation statements)

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“…Tungsten borides have earth-abundant compositions and are known for their mechanical hardness and thermal/electrical properties. , Tungsten borides with varying stoichiometries, including W 2 B, W 2 B 5 , and WB 4 , have been synthesized by a solid reaction between tungsten and amorphous boron powders. , Among these tungsten borides, WB was found to exist in a single crystalline phase, and the crystallinity was found to be enhanced with increasing both the time and the temperature of heat treatment . WB crystallizes in either an orthorhombic high-temperature phase or a tetragonal low-temperature phase.…”

Section: Introductionmentioning

confidence: 99%

“…13,14 Among these tungsten borides, WB was found to exist in a single crystalline phase, and the crystallinity was found to be enhanced with increasing both the time and the temperature of heat treatment. 14 WB crystallizes in either an orthorhombic high-temperature phase or a tetragonal lowtemperature phase. The latter is stable up to 2170 °C, when the phase transition occurs.…”

Section: ■ Introductionmentioning

confidence: 99%

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Hydrogen Evolution on Restructured B-Rich WB: Metastable Surface States and Isolated Active Sites

Zhang¹,

Cui²,

Jimenez−Izal

et al. 2020

ACS Catal.

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Borides have been recently identified to be a class of earth-abundant and low-cost materials that are surprisingly active towards oxidative dehydrogenation, and hydrogen evolution reaction (HER) catalysis. Here we explain from first principle calculations the HER activity of WB, an industrial material known for its superior physical properties and chemical inertness. We find that, compared to bulk termination, a major surface reconstruction takes place, leading to the offstoichiometric B-rich surface termination that contains the active sites. The hydrogen adsorbate configurations are further investigated under various adsorbate coverages. Many competing configurations appear to be accessible in reaction conditions, and thus, a grand canonical ensemble is established to describe the catalytic system. A phase diagram of adsorbate coverages is constructed as a function of pH and applied potential. A complex reaction network is presented based on the ensemble-averaged reaction rates, and the electrocatalytic activities are evaluated under different overpotentials. The major contributors to the activity are found to be a few metastable surface states with distinct electronic structure that are only accessible at high adsorbate coverages in reaction conditions. In addition, while the activity of the dominant active site is nearly the same as on the unreconstructed WB, the B-rich formations play an important role of isolating the active sites, and preventing the passivation of the surface with bubble of forming H 2 .

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