Stable Iron Hydroxide Nanosheets@Cobalt‐Metal–Organic–Framework Heterostructure for Efficient Electrocatalytic Oxygen Evolution

Abstract Most studies are devoted to the use of metal–organic frameworks (MOFs) as templates to construct desirable electrocatalysts in situ by high‐temperature pyrolysis. The emergence of heterostructures invokes new opportunities to use the full potential of pristine MOFs as efficient catalysts in the oxygen evolution reaction (OER). Here, a MOF surface‐reaction strategy is developed to synthesize MOF‐based heterostructures without pyrolysis. Uniform Fe(OH) 3 nanosheets are grown controllably on the Co‐MOF‐74 surface by a fast “phenol–Fe” reaction that takes advantage of the hydroxyl sites in Co‐MOF‐74. The resulting Fe(OH) 3 @Co‐MOF‐74 heterostructure delivers an excellent performance in the OER with a low overpotential of 292 mV at 10 mA cm −2 . Notably, the introduction of Fe can improve the intrinsic activity of the original Co atom significantly. The turnover frequency in Fe(OH) 3 @Co‐MOF‐74 (1.209 s −1 ) is more than 25 times higher than that in Co‐MOF‐74 (0.048 s −1 ). This work presents a fresh concept for the fundamental design of advanced pure‐MOF‐based heterostructures and, thereby, provides a new avenue for the fabrication of other energy‐conversion and ‐storage materials.