Borate Anion Dopant Inducing Oxygen Vacancies over Co3O4 Nanocages for Enhanced Oxygen Evolution

Abstract

The rational design of cost effective and highly efficient oxygen evolution reaction (OER) catalysts plays an extremely important role in promoting the commercial applications of electrochemical water splitting. Herein we reported a sacrificial template strategy for the preparation of borate anion doped Co3O4@ZIF-67 nanocages assembled with nanosheets (B-Co3O4@ZIF-67) by hydrothermal boronation of zeolitic imidazolate framework-67 (ZIF-67). During the preparation process, two different kinds of borate anion sources were found to regulate the morphological structures by tuning the etching rate between ZIF precursors and the borate anion. Moreover, borate anion doping was also found to induce oxygen vacancy defects, which is beneficial for modulating the electronic structure and accelerating electron transport. Meanwhile, the resultant B-Co3O4@ZIF-67 nanocages possess a large specific surface area, which is beneficial for the mass transfer of the electrolyte and exposing more catalytic active sites. Benefiting from the advantages above, the resultant B-Co3O4@ZIF-67 nanocages exhibit impressive OER performance with a small overpotential of 334 mV, a current density of 10 mA cm−2, a small Tafel slope of 73.88 mV dec−1, as well as long-term durability in an alkaline electrolyte.