Co₃O_4–x-Carbon@Fe_2–yCo_yO₃ Heterostructural Hollow Polyhedrons for the Oxygen Evolution Reaction

Hollow heterostructured nanomaterials have received tremendous interest in new-generation electrocatalyst applications. However, the design and fabrication of such materials remain a significant challenge. In this work, we present Co 3 O 4– x -carbon@Fe 2– y Co y O 3 heterostructural hollow polyhedrons that have been fabricated by facile thermal treatment followed by solution-phase growth for application as efficient oxygen evolution reaction (OER) electrocatalysts. Starting from a single ZIF-67 hollow polyhedron, a novel complex structured composite material constructed from Co 3 O 4– x nanocrystallite-embedded carbon matrix embedded with Fe 2– y Co y O 3 nanowires was successfully prepared. The Co 3 O 4– x nanocrystallite with oxygen vacancies provides both heterogeneous nucleation sites and growth platform for Fe 2– y Co y O 3 nanowires. The resultant heterostructure combines the advantages of Fe 2– y Co y O 3 nanowires with the large surface area and surface defects of Co 3 O 4– x nanocrystallite, resulting in improved electrocatalytic activity and electrical conductivity. As a result, such novel heterostructured OER electrocatalysts exhibit much lower onset potential (1.52 V) and higher current density (70 mA/cm 2 at 1.7 V) than Co 3 O 4– x -carbon hollow polyhedrons (onset 1.55 V, 35 mA/cm 2 at 1.7 V) and pure Co 3 O 4 hollow polyhedrons (onset 1.62 V, 5 mA/cm 2 at 1.7 V). Furthermore, the design and synthesis of metal–organic framework (MOF)-derived nanomaterials in this work offer new opportunities for developing novel and efficient electrocatalysts in electrochemical devices.