Ni/Mo Regulated Nb₃₅Hf₃₀Co₁₅Ni_20-xMo_x High-Entropy Alloy Membranes for High Hydrogen Permeability and Hydrogen Embrittlement Resistance

Efficient hydrogen separation and purification technology plays a crucial role in the hydrogen energy industry. VB-group alloy membranes have demonstrated favorable hydrogen permeability, but their hydrogen embrittlement resistance remains generally insufficient. This work designed Nb₃₅Hf₃₀Co₁₅Ni_20-xMo_x high-entropy alloy (HEA) membranes with regulated Ni and Mo contents. The influences of HEA compositions on microstructures, hydrogen permeability and hydrogen embrittlement resistance were systematically analyzed. On the one hand, the doping of Mo increased the volume and proportion of BCC-Nb phase, thus promoting hydrogen permeation; on the other hand, the hydrogen solubility was reduced, thus enhancing the hydrogen embrittlement resistance. The lattice distortion effect, sluggish diffusion effect and optimized Mo content collectively enhanced the comprehensive performance of Nb₃₅Hf₃₀Co₁₅Ni_12.5Mo_7.5, achieving a hydrogen permeability (Φ) of 2.68 × 10⁻⁸ mol H₂ m⁻¹·s⁻¹·Pa^−0.5 at 673 K and exhibiting excellent hydrogen embrittlement resistance, showing no hydrogen-induced fractures even at room temperature. This quantitatively demonstrates its excellent performance, which represents a certain breakthrough compared to related studies. The novel Nb₃₅Hf₃₀Co₁₅Ni_20-xMo_x HEA membranes offer excellent hydrogen permeability and improved hydrogen embrittlement resistance, thereby highlighting the potential for future hydrogen purification applications.