The bio-inspired heterogeneous single-cluster catalyst Ni100-Fe₄S₄ for enhanced electrochemical CO₂ reduction to CH₄

Electrochemical conversion of CO₂-to-CH₄ is a process of converting the inert greenhouse gas into energy molecules. It offers great promise for the transformation of carbon-neutral economy. However, achieving high CH₄ activity and selectivity remains a major challenge because the electrochemical reduction of CO₂-to-CH₄ is accompanied by various C₁ intermediates at the catalytic site, involving multiple proton-coupled electron transfer processes. Herein, different from the traditional designing strategy, we propose a bio-inspired theoretical design approach to construct a heterogeneous single-cluster catalyst Ni100-Fe₄S₄ at the atomic level, which may show high CO₂ electroreduction performance. Combined with the crystallographic data and theoretical calculations, Ni100-Fe₄S₄ and CO dehydrogenase exhibit highly similar catalytic geometric active centers and CO₂ binding modes. By exploring the origin of the catalytic activity of this biomimetic structure, we found that the activation of CO₂ on Ni100-Fe₄S₄ theoretically exceeds that on natural CO dehydrogenase. Density functional theory calculations reveal that the dehydrogenase enzyme-liked Fe-Ni active site serves as an electron enrichment 'electro-bridge' (an electron-rich highly active catalytic site), which can activate CO₂ molecules efficiently and stabilize various intermediates in multistep elementary reactions to selectively produce CH₄ at a low overpotential (0.13 eV). The calculated CO₂ electroreduction pathways are well consistent with the nickel-based catalytic materials reported in experimental studies. Our work showcases and highlights the rational design of high-performance catalytic materials via the biomimetic methodology at the atomic level.