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

Abstract

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 CoO-carbon@FeCoO 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 CoO nanocrystallite-embedded carbon matrix embedded with FeCoO nanowires was successfully prepared. The CoO nanocrystallite with oxygen vacancies provides both heterogeneous nucleation sites and growth platform for FeCoO nanowires. The resultant heterostructure combines the advantages of FeCoO nanowires with the large surface area and surface defects of CoO 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 at 1.7 V) than CoO-carbon hollow polyhedrons (onset 1.55 V, 35 mA/cm at 1.7 V) and pure CoO hollow polyhedrons (onset 1.62 V, 5 mA/cm 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.

Synthesis of ultrathin Co2AlO4 nanosheets with oxygen vacancies for enhanced electrocatalytic oxygen evolution

“…. ARTICLES (Table S1) [27,33,[41][42][43][44][45][46][47][48][49][50][51][52][53][54][55]. The results indicated that the VO-rich Co 2 AlO 4 possessed a high OER kinetics.…”

Electrochemical Energy Conversion and Storage with Zeolitic Imidazolate Framework Derived Materials: A Perspective

“…The large surface area and surface defects of the Co 3 O 4–x nanocrystallite improved the electrocatalytic activity and electrical conductivity of the hetero‐structured hybrid. In addition, the synergistic effects of the two nanocomponents resulted in a high OER current density of 70 mA cm −2 at 1.7 V, which is significantly higher than Co 3 O 4‐x ‐carbon hollow polyhedrons and pure Co 3 O 4 hollow polyhedrons …”

“…It is important to note that the heating temperature and ramping rate are crucial to control the size and dispersion of the nanoparticles. To prepare various functional materials, other synthetic steps are often applied on pre‐formed Co@NC, such as simple annealing in air to form Co‐oxide@NC or even Co 3 O 4–x /carbon . Introduction of oxygen vacancies in the cobalt oxide spinel improves the conductivity of the material and also provides the nucleation sites for the second metal oxides as demonstrated by Xu et al .…”

“…To prepare various functional materials, other synthetic steps are often applied on pre‐formed Co@NC, such as simple annealing in air to form Co‐oxide@NC or even Co 3 O 4–x /carbon . Introduction of oxygen vacancies in the cobalt oxide spinel improves the conductivity of the material and also provides the nucleation sites for the second metal oxides as demonstrated by Xu et al . In this method, the final product Co 3 O 4–x carbon@Fe 2–y Co y O 3 nanofibers retained the polyhedral morphology, and hollow cobalt oxide/carbon shells with numerous Fe 2–y Co y O 3 nanofibers were generated on the surface.…”

“…In addition, the synergistic effects of the two nanocomponents resulted in a high OER current density of 70 mA cm À 2 at 1.7 V, which is significantly higher than Co 3 O 4-x -carbon hollow polyhedrons and pure Co 3 O 4 hollow polyhedrons. [52] In electrocatalysis, multi-shell structures are advantageous due to the easy penetration of electrolyte, increased exposure of the catalytic sites in the electrolytes and easy mass transport. [53] By tuning the reaction of ZIF-67 and Ni 2 + ions, Wang et al successfully prepared ZIF-67@NiCo-LDH, which was further transformed into Co 3 O 4 /NiCo 2 O 4 double shelled nanocages (DSNCs) after annealing in air.…”