All molybdenum borides with various phases such as Mo₂B, α-MoB, β-MoB, and MoB₂ have been found to possess excellent electrocatalytic hydrogen evolution reaction (HER) activity. Ultrathin two-dimensional (2D) borides are expected to have both maximized surface active sites and fast electron transport, ensuring higher HER activity. Here we report the large-area preparation of ultrathin hexagonal Mo₃B films of 6.48 nm thickness on Mo foils by chemical vapour deposition using a mixture of boron and boron oxide powders as the boron source, and hydrogen gas as both the carrier and reducing gas. The ultrathin film exhibits fantastic stability in acidic solution and has a small Tafel slope of 52 mV dec⁻¹ which is the lowest value so far reported for molybdenum boride catalysts. Furthermore, our first-principles calculations show that the ultrathin Mo₃B film is metallic, which facilitates fast electron transport along the active edges of the thin film for enhancing the HER activity.

中文翻译：

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超薄硼化钼薄膜，用于高效催化析氢反应

已发现所有具有各种相的硼化钼（例如Mo ₂ B，α-MoB，β-MoB和MoB _2）都具有出色的电催化放氢反应（HER）活性。预计超薄二维（2D）硼化物将具有最大化的表面活性位点和快速的电子传输能力，从而确保更高的HER活性。在这里，我们报告了通过使用硼和氧化硼粉末的混合物作为硼源以及氢气作为载流子和还原性气体的混合物进行化学气相沉积，在Mo箔上大面积制备厚度为6.48 nm的超薄六角形Mo ₃ B膜的方法。超薄薄膜在酸性溶液中表现出出色的稳定性，并具有5​​2 mV dec ^-1的小Tafel斜率这是迄今为止报道的硼化钼催化剂的最低值。此外，我们的第一性原理计算表明，超薄Mo ₃ B膜是金属的，这有助于沿着薄膜的活性边缘快速进行电子传输，从而增强HER活性。