Assembled 3D MOF on 2D Nanosheets for Self-boosting Catalytic Synthesis of N-doped Carbon Nanotube Encapsulated Metallic Co Electrocatalysts for Overall Water Splitting

A binder-free electrode with metallic Co embedded in N-doped carbon nanotube array ([email protected]) was fabricated via an electrodeposition, stereoscopic assembly and self-boosting catalytic pyrolysis. Specifically, directed-eletrodeposition vertical growth of Co(OH)2-nanosheet serves as the structure inducer to offer abundant sites for ZIF-67 growth, and melamine is selected as an initiator for orientated growth of N-CNTs. As an integrative non-noble electrocatalyst for water splitting, it requires only 1.58 V to achieve 30 mA cm−2 in an alkali-electrolyzer. The remarkable electrochemical performance is mainly attributed to the unique 3D hierarchical tubular structure and the synergistic effect of each chemical compositions, which provide amount of accessible active sites, accelerate the diffusion of electron/electrolyte, and improve the electrical conductivity, hydrophilicity and structural stability. The electro-catalytic splitting water mechanism was further explored by density functional theory. This universal method can be extensively applied to fabricate well-defined monometal or bimetal encapsulated into N-CNTs for various electrochemical applications.