Engineering Facets and Oxygen Vacancies over Hematite Single Crystal for Intensified Electrocatalytic H 2 O 2 Production

Hydrogen peroxide is a highly valuable chemical, and electrocatalytic oxygen reduction towards H 2 O 2 offers an alternative method for safe on‐site applications. Generally, low‐cost hematite (α‐Fe 2 O 3 ) is not recognized as an efficient electrocatalyst because of its inert nature, but it is herein reported that α‐Fe 2 O 3 can be endowed with high catalytic activity and selectivity via the engineering of facets and oxygen vacancies. Density‐functional theory (DFT)calculations predict that the {001} facet is intrinsically selective for H 2 O 2 production, and that oxygen vacancies can trigger the high activity, providing sites for O 2 adsorption and protonation, stabilizing the *OOH intermediate, and preventing cleavage of the OO bond. The synthesized oxygen‐defective α‐Fe 2 O 3 single crystals with exposed {001} facets achieve high selectivities for H 2 O 2 of >90%, >88%, and >95% in weakly acidic, neutral, and alkaline electrolytes, respectively, and the H 2 O 2 production rate reaches 454 mmol g −1 cat h −1 at 0.1 V versus RHE under alkaline conditions. In an anion exchange membrane fuel cell, a maximum H 2 O 2 production of 546.8 mmol L −1 with a high Faradaic efficiency of 80.5% is achieved. Thus, this work details a low‐cost catalyst feasible for H 2 O 2 synthesis, and highlights the feasibility of theoretical catalyst design for practical applications.