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Reducing Mn2+ ions were doped to tailor the electronic structure of Ni and Fe sites in NiFe-layered double hydroxides.

Introducing oxygen vacancies to metal oxide materials would improve their catalytic activity but usually needs reductive reagents (e.g., H2) and high temperatures (e.g., >600 °C), which is unsafe, complex, and time consuming. Herein, a fast (30 s) and facile (operated at ambient conditions) flame‐engraved method is used to introduce abundant oxygen vacancies and well‐defined hexagonal cavities with (110) edges to nickel–iron layered double hydroxides (NiFe‐LDH). Abundant oxygen vacancies, lower coordination numbers, and electron‐rich structures of Ni and Fe sites emerge in the flame‐engraved NiFe‐LDH array electrode, leading to its onset potential as low as 1.40 V (vs reversible hydrogen electrode) for oxygen evolution reaction. This highlights the importance and convenience of flame‐engraving method in preparing metal hydroxides with abundant oxygen vacancies, which can be used as efficient electrochemical catalysts.