Ultrafast Synthesis of Nanoscale Metal Borides for Efficient Hydrogen Evolution

Nanoscale metal borides, with exceptional physicochemical properties, have been attracted widespread attention. However, traditional synthesis methods of metal borides often lead to surface coking and large particle sizes. Herein, we have employed a flash Joule heating (FJH) technique to enable the ultrafast synthesis of metal boride nanomaterials. The synthesized materials encompass a wide range of diverse categories, including alkaline-earth metal borides (CaB₆), transition metal borides (TiB₂, VB₂, CrB₂, MoB, MoB₂, MnB₂, MnB₄, FeB, CoB, NiB), noble-metal borides (RuB₂, RuB_1.1), and rare-earth metal borides (LaB₆, CeB₆). As an example, the RuB₂ demonstrates highly desirable electrocatalytic performance for all-pH hydrogen evolution reaction (HER). Especially, under the acidic condition, it exhibits an overpotential as low as 15 mV at a current density of 10 mA cm^-2, with a nearly 100 % faradic efficiency. Additionally, in situ Raman spectra confirm that both Ru and B sites serve as active sites for the HER. Moreover, the stability of RuB₂ can be further enhanced by optimizing the microenvironments of the anolyte composition (H⁺, K⁺). More importantly, the experimental and density functional theory (DFT) calculations reveal that the co-existence of H⁺ and K⁺ localized around the RuB₂ plays a crucial role in further enhancing the stability.