Mechanochemical coordination self-assembly for Cobalt-based metal-organic framework-derived bifunctional oxygen electrocatalysts

The exploration and preparation of inexpensive, high-performance and stable catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is of significant imperativeness, yet is still on the way. In this study, a facile operation protocol is presented for constructing an exquisite three-dimensional coral reef-like carbon nanotube assembly bridged with N-doped graphene (assigned as 3D CNTAs-NG, which represented carbonization products at 900℃) as highly efficient and durable ORR/OER electrocatalysts. It does not require the introduction of reductive atmosphere. In this tactic, the dicyanamide ligand on the Co-MOF not only was instrumental in the introduction of nitrogen but also acted as the inducer of carbon nanotubes (CNTs) to lock the metallic Co in graphitic carbon layers. Graphene oxide (GO) is chosen as a matrix to pin the CNTs and ensure the uniform distribution of CNTs. The obtained CNTAs-NG structure possesses 3D open porous texture, abundant defects, desired nitrogen bonding type and high specific surface area, providing them with excellent ORR and OER properties. As such, the optimized 3D CNTAs-NG sample shows high onset potential (Eonset = 0.97 V vs. RHE) and half-wave potential (E1/2 = 0.85 V vs. RHE) for ORR and overpotential of 340 mV at 10 mA∙cm-2 for OER. Meanwhile, the prepared optimum catalyst exhibited outstanding durability for ORR and OER in alkaline solutions. This work may pave significant concepts for the synthesis of highly active bifunctional electrocatalysts with intriguing architectures and compositions.