A Ni-N-C catalyst for CO₂ electroreduction based on the MOF@MOF configuration exhibiting wide active reaction sites

CO production, which is known for its efficient use of fewer electrons, has garnered significant attention owing to its potential applications in downstream industries. This study introduces a novel method for synthesizing the Ni-N-C structure with Ni, using a porous metal-organic framework (MOF) and a zeolitic imidazolate framework (ZIF), which is a type of material under MOFs, with the structural configuration of MOF@MOF. Decoupling the inner electron-transfer paths from the outer active sites makes it possible to obtain a high partial current for CO while minimizing the content of Ni. In addition, the pyrolyzed host MOF has superhydrophobic properties, making the inner space of Ni-N-C-748 a favorable environment for CO₂ that prevents the hydrogen evolution reaction. Consequently, Ni-N-C-748 exhibited a faradaic efficiency for CO greater than 95% over a wide potential range. Furthermore, a potential of 2.1 V was obtained at 100 mA cm⁻² using a membrane electrode assembly cell.