Rational Design and Dynamic Ru Exsolution Enables Active Heterostructures Surpassing Pt for Alkaline Hydrogen Evolution

Accelerating the hydrogen evolution reaction (HER) is essential for improving water electrolysis efficiency with renewable energy, ensuring a sustainable hydrogen economy. Heterostructure catalysts show promise in significantly enhancing alkaline HER by facilitating both water dissociation and hydrogen generation, but the rational design and synthesis of robust and active heterostructures remains challenging. Here, we correlate the bias-driven dynamic surface reconstruction of ruthenate perovskites with their O 2<i>p</i> band center to design exsolved Ru/perovskite heterostructures for highly efficient alkaline HER. BaRuO₃ is used as a model because its O 2<i>p</i> band center is closest to the Fermi level, allowing facile surface reconstruction under HER conditions. This results in exsolved Ru on BaRuO₃ with rich oxygen vacancies, as confirmed by microscopy and spectroscopy, including <i>in situ</i> Ru exsolution over time under transmission electron microscopy observation. The target heterostructure shows approximately 120-fold enhancement in HER activity after surface reconstruction, with a mass activity of ∼ 1.68 times higher than commercial Pt/C at an overpotential of 80 mV. We reveal that perovskite oxides facilitate water dissociation and the exsolved Ru promotes hydrogen generation. Moreover, this bias-driven dynamic reconstruction strategy is applicable to other perovskite oxides. These findings provide guidelines for the rational design of efficient heterostructure electrocatalysts and identify the electronic structure descriptor for oxide catalyst exsolution behavior.