Transition metal-based high entropy alloy microfiber electrodes: Corrosion behavior and hydrogen activity

Highlights: • Ultra-high corrosion resistance down to 1.85 µm yr^–1 of TiZrNbVTa(Hf) HEAs in 1 M KOH. • Formation of a few nanometers passive oxide layer accounts for corrosion stability. • High hydrogen activity due to low cathodic Tafel slope & large transfer coefficient. • Gas-solid reactions confirm high hydrogen storage of 1.7 wt%. • High corrosion stability in 0.5 M H₂SO₄ (0.148 mm yr^–1) & 0.9 wt% NaCl (0.081 mm yr^–1). This contribution reveals ultra-high corrosion resistance of high entropy alloys (HEAs), i.e. Ti₂₀Zr₂₀Nb₁₅V₁₅Hf₁₅Ta₁₅ of 1.85 µm yr^–1 in alkaline environment, adverting their use for battery/fuel cell components. Formation of several nanometers passive oxide layer confirmed by scanning transmission electron microscopy accounts for corrosion resistance which increases with TiO_x content. Cathodic Tafel slope of 67 mV dec^–1 and large transfer coefficient of 0.82 obtained for Ti₂₀Zr₂₀Nb₂₀V₂₀Ta₂₀ suggest its use for hydrogen electrocatalysis. High amounts of hydrogen storage, 1.7 wt% in Ti₂₅Zr₂₅Nb₁₅V₁₅Ta₂₀, were confirmed by gas-solid reactions. This HEA also has high corrosion resistance in acidic and saline environments ideal for coatings and surgical tools/implants.