Ferrocene-Engineered Bimetallic MOF Nanoflowers Boost Selective CO2-to-CH4 Electrocatalysis via Dual-Metal Synergy and Structural Precision.

Abstract

Electrocatalytic CO2 reduction to methane (CH4) is a promising route for sustainable energy conversion and carbon neutrality. However, limited control over intermediates and competition from the hydrogen evolution reaction (HER) restrict selectivity and efficiency. To address these challenges, a ferrocene-based bimetallic metal-organic framework MOF catalyst (NixIny-Fc/NF) with a hierarchical nanoflower architecture is developed, where dual-metal synergy modulates the electronic structure at active sites. Incorporating redox-active ferrocene units and optimizing the Ni/In ratio enhances active-site accessibility and tunes the electronic environment. Structural and compositional analyses, including scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), confirm that Ni5In3-Fc/NF possesses a 3D porous nanoflower morphology, while X-ray photoelectron spectroscopy (XPS) reveals electronic interactions between Ni and In. Electrochemical tests show that the catalyst achieves 76% CH4 Faradaic efficiency at -0.8 V versus RHE and suppresses H2 evolution. Ni5In3-Fc/NF maintains stability and CH4 selectivity over 16 000 s of electrolysis. Density-functional theory (DFT) indicates that the bimetallic interface reduces the energy barrier for the rate-limiting *CO formation step, thereby accelerating the CO2-to-CH4 pathway. This study presents a synergistic strategy integrating dual-metal interaction and structural precision to enhance performance and durability in CO2 electroreduction, offering insights into the rational design of high-performance MOF catalysts.