Metal‐Organic Framework‐Templated Hollow Co₃O₄/C with Controllable Oxygen Vacancies for Efficient Oxygen Evolution Reaction

Abstract

Hydrogen production from water splitting is one of the effective methods to solve energy and environmental problems. However, the large overpotential of oxygen evolution reactions (OER) seriously impedes their development and application. Therefore, it is crucial to find a catalyst with low cost and high stability for OER. Herein, we report a simple method to fabricate a series of porous catalysts encapsulated with Co 3 O 4 nanoparticles by carbonizing and then oxidizing MOF precursors, which can regulate and produce a large number of oxygen vacancies. The overpotentials of Z67-Co 3 O 4 /C-4 and Z9-Co 3 O 4 /C-4 are only 353and 349 mV at a current density of 10 mA cm À 2 with a small Tafel slope of 60 and 67 mV dec À 1 , respectively. These excellent properties can be attributed to the graphite carbon and unique hollow structure, as well as more water molecules adsorbed by oxygen vacancies, which effectively improve the conductivity and electron transfer and further promote OER activity. Thus, this preparation strategy can be applied to various MOF catalysts to regulate oxygen vacancies and thereby expanding their application in a wider range of fields.

Metal-organic framework nanocrystal-derived hollow porous materials: Synthetic strategies and emerging applications

“…In addition, Yao and colleagues prepared two types of hollow Co 3 O 4 /C (Z67-Co 3 O 4 /C-4 and Z9-Co 3 O 4 /C-4) via carbonized and then oxidized ZIF-67 and ZIF-9 precursors. 55 Figures 7 D and 7E demonstrate that the catalysts of Z67-Co 3 O 4 /C-4 and Z9-Co 3 O 4 /C-4 exhibited excellent activity for OER. This is because the unique hollow porous carbon structure improves the electron transfer rate, and vast oxygen vacancies in hollow Co 3 O 4 /C can improve the adsorption of water molecules to promote OER activity.…”

“…After further annealing treatment under air, the final sample NiO/Ni/graphene composites were acquired. 49 Moreover, hollow ZnO/C composites, 53 NiO x /Ni@C composites, 54 Z67-Co 3 O 4 /C-4, and Z9-Co 3 O 4 /C-4 55 were also synthesized by a similar process. Similarly, Yu et al.…”

“… 47 (D and E) Summarized overpotentials at j = 10 mA cm −2 and Tafel plots of Z67-Co 3 O 4 /C-4 and Z9-Co 3 O 4 /C-4 in 1 M KOH solution. 55 (F) SEM, TEM, and mapping of Ni-Fe LDH nanocages. (G) CV curves of Ni-Fe LDH catalysts and carbon paper.…”

“… (D and E) Summarized overpotentials at j = 10 mA cm −2 and Tafel plots of Z67-Co 3 O 4 /C-4 and Z9-Co 3 O 4 /C-4 in 1 M KOH solution. 55 …”

Trimetallic Nanoparticles Encapsulated into Bamboo‐Like N‐Doped Carbon Nanotubes as a Robust Catalyst for Efficient Oxygen Evolution Electrocatalysis

“…Coordination polymers, or metal-organic frameworks (MOFs) have been approved to be ideal precursors and templates for carbon-based nanocomposites due to their intrinsic well-tunable chemical structures and morphologies, high porosity, as well as large specific surface areas. [24][25][26][27][28] Moreover, after pyrolysis under the inert gas atmosphere, the heteroatom (such as N, P, S) doped organic ligands in MOFs will be directly converted into heteroatom-doped porous carbon without additional treatment. [29] For example, Ning et.…”