Ni-Based Nanoparticle-Embedded N-Doped Carbon Nanohorns Derived from Double Core–Shell CNH@PDA@NiMOFs for Oxygen Electrocatalysis

The development of highly efficient electrocatalysts for the oxygen evolution reaction (OER) plays a crucial role in many regenerative electrochemical energy-conversion systems. Herein, we report a novel double core-shell-structured CNH@PDA@NiMOF (CNH-D-NiMOF) composite based on the support of carbon nanohorns (CNHs) and the direction of polydopamine (PDA) on the synthesis of metal-organic frameworks (MOFs). It is found that this unique structure improves the electrocatalytic performance and stability of the composites. Furthermore, a controlled partial pyrolysis strategy was proposed to construct the Ni-based nanoparticle-embedded N-doped CNHs. The partial pyrolysis method preserves the framework structure of MOFs for effective substrate diffusion while producing highly active nanoparticles. This leads to the result that the Ni-based nanoparticle-embedded N-doped CNHs possess higher stability and significantly improved electrocatalytic properties. Among these derivatives, the sample prepared at a pyrolysis temperature of 400 °C (named as CNH-D-NiMOF-400) outperforms most of the reported unprecious-metal catalysts. At current densities of 20 and 100 mA·cm^-2, the overpotentials of CNH-D-NiMOF-400 are 270 and 340 mV for the OER on a carbon fiber paper (CFP), respectively. The outstanding electrocatalytic properties above suggest that this composite is an excellent candidate for the substitution of noble metal-based catalysts for OER.