Atomic phosphorus induces tunable lattice strain in high entropy alloys and boosts alkaline water splitting

High entropy alloys (HEAs) recently emerges as a potential platform to construct multifunctional electrocatalysts owing to their unique inherent complexity. Herein, a strain engineering strategy is reported to design and fabricate P-doped porous HEA electrodes with tunable heteroatom loadings and lattice strains, thus tailoring the intrinsic electronic structure and boosting the catalytic properties of HEA. Instead of forming phosphides, graded distribution of tensile strain is observed in the porous HEA after P doping, as confirmed by various experimental measurements and the first-principles calculation results. Benefiting from the introduction of heteroatoms and the induced lattice strain, the exposed electrocatalytic active area and intrinsic specific activity of P-doped porous HEA have been greatly enhanced in the meantime. As a result, the obtained 1P-HEA electrode exhibited excellent alkaline hydrogen and oxygen evolution reaction activity, requiring low overpotentials of 70 mV and 211 mV at 10 mA cm-2, respectively. Additionally, a full water splitting electrolyzer constructed based on bifunctional 1P-HEA electrodes outperforms commercial Pt/C and RuO2 counterparts and remains almost 100% activity after continuous 84 h of stability testing at an ultrahigh current density of 2 A cm-2 under simulated industrial condition. A facile P-doped method is adopted to modulate the lattice strain of porous HEA, tensile strain caused by the introduced hetero-anion atoms is verified by multiple characterizations. Benefitting from the co-effects of strain and hetero-anion doping, the as-synthesized P-doped HEA exhibits boosted water splitting catalytic activity and excellent stability under an industrial current density (2 A cm-2, 84 h).