High hydrogen evolution of metastable AlB2-type WB2 and its Fe-containing solid solution

Abstract

Theoretical calculations have shown that AlB₂-type WB₂ (P6/mmm, α-WB₂) exhibits superior hydrogen evolution reaction (HER) performance compared to WB₂-type (P6₃/mmc, β-WB₂). However, due to its metastable nature and the challenges associated with large-scale synthesis, α-WB₂ has been largely overlooked. In the present work, α-W_1−xFe_xB₂ (x = 0, 0.1, 0.2, and 0.3) powders were synthesized using high-energy ball milling (HEBM) technology. Self-supporting electrodes were then prepared via spark plasma sintering (SPS) at 750 °C in an Ar atmosphere. Experimental results showed that α-WB₂ demonstrated a high catalytic activity with an overpotential of 108.1 mV, which is much lower than that of β-WB₂ (141.6 mV) at a current density of 10 mA cm⁻² in an acidic medium. Furthermore, the sample doped with 20 mol% Fe achieved better HER performance, with an overpotential as low as 88.1 mV. The experimental results confirmed that the fully layered structure of α-WB₂ possessed excellent HER performance. Combined with transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) analysis, it can be concluded that Fe doping enhances the catalytic activity of active sites.