Designing Boride Electrocatalysts for Hydrogen Evolution скачать в хорошем качестве

Designing Boride Electrocatalysts for Hydrogen Evolution

Abstract: The electrolysis of water is considered as a clean mean for large scale hydrogen gas production. However, this large-scale production is still hindered by the high cost and scarcity of noble metal catalysts such as Pt. Recently, non-noble metal materials have emerged as highly active electrocatalysts (AlB2-type) for the hydrogen evolution reaction (HER) to produce hydrogen. Our recent research found that a‑MoB2 [1] exhibits high HER activity. In addition, density functional theory (DFT) calculations show that several surfaces of MoB2 are active and the optimum evolution of H2 occurs on the graphene-like B-terminated {001} surface. Furthermore, DFT and experiments demonstrate that a‑MoB2 is more HER active than b-MoB2 [2], due to the presence of 50% more graphene-like boron layers in the former It was recently also found that FeB2 is highly active for overall water splitting in basic solution. However, TiB2 is not as active as MoB2 for HER. To examine the distinct activities of metal diboride as HER electrocatalysts and how the metals could affect the graphene-like boron layer, DFT was applied to investigate the H-surface adsorption process on MB2 (M = Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W). Our results indicate that the H-surface binding energy decreases as the electronegativity of the metal increases. Therefore, the electron transfer between metal and boron is one of the key parameters to control the HER activity of MB2. Using a recently developed synthesis, [3] we were able to synthesize most of the above-mentioned diborides at the nanoscale. VB2 behaves similarly to MoB2, thus it was predicted by DFT to be a highly active HER catalyst candidate and confirmed by experiments. Subsequently, an unexpected boron-chain dependency of the HER activity was discovered in vanadium borides, that enabled not only the prediction of the HER activity of unstudied V2B3 but also those of other hypothetical “VxBy” were predicted using an exponential equation that predicts the overpotentials of known and hypothetical VxBy phases containing at least a boron chain. [4] We have also recently discovered an unexpected lattice parameter-dependency on HER of ternary variants with the AlB2-type structure that has enabled an excellent boride HER electrocatalyst that outperforms Pt/C at high current density. [5] Keywords: Hydrogen evolution, Borides, Electrocatalysis, AlB2-type, Current density. Full Article: https://www.proceedings.iaamonline.or...