Core-Shell Engineering of ZIF-67@N-Doped Hollow Carbon Spheres via Diffusion Strategy for Enhanced Oxygen Evolution Reaction.

Metal-organic frameworks (MOFs) serve as versatile precursors for creating long-lasting electrocatalysts. Core-shell engineering is a unique method for activating MOFs for electrocatalytic applications without altering their fundamental characteristics. Encapsulating MOFs in nitrogen-doped hollow carbon spheres (N-HCS) improves electrocatalyst performance by modulating the band structure. We synthesized a ZIF-67@N-HCS catalyst by embedding nanocrystals into nitrogen-doped hollow carbon spheres using a diffusion-driven, space-confined approach. For the electrocatalytic oxygen evolution reaction (OER), the ZIF-67@N-HCS catalyst shows decreased overpotential of 290 mV to reach the current density of 20 mA cm⁻² and better reaction kinetics, as demonstrated by a lower Tafel slope value of 86 mV dec⁻¹. The catalyst has a high electrochemically active surface area (ECSA) of 320 cm² and an electric double-layer capacitance of 12.8 mF cm⁻². This study proposed a strategy of core-shell engineering, which has the potential to improve the efficiency of electrocatalysts for water oxidation.