Solid-Solution Engineering of Earth-Abundant Metal Borides of Y(TM₁TM₂)B₄‑Type as Durable High-Current-Density Electrocatalysts for HER

Herein, we develop a series of arc-melted solid-solution transition-metal borides, YCr_1–<i>x</i>Mo_<i>x</i>B₄, YCr_1–<i>x</i>W_<i>x</i>B₄, and YMo_1–<i>x</i>W_<i>x</i>B₄ (<i>x</i> = 0.25, 0.5, and 0.75), as robust HER electrocatalysts for acidic media.

Through solid-solution engineering, the catalytic performance of the parent borides is significantly improved, with each composition outperforming commercial 20 wt % Pt/C at high current density. Notably, YCr_0.25W_0.75B₄ exhibits the best overall HER performance, requiring only 0.449 V overpotential to reach 1000 mA/cm², compared with 0.742 V for 20 wt % Pt/C. The enhanced activity is further supported by a high double-layer capacitance of 54 mF/cm², reflecting increased electrochemically accessible surface area and abundant exposed HER-active sites.