Investigation of Mn-Modified Bimetallic ZIF-۶۷ Structures as Supercapacitor

The development of high-performance electrode materials is essential for advancing next-generation energy storage systems. In this study, bimetallic Co/Mn ZIF-۶۷ with tunable Co:Mn ratios were successfully synthesized to investigate the effect of Mn incorporation on structural and electrochemical properties. Structural analyses reveal that Mn۲+ is homogeneously incorporated into the ZIF-۶۷ framework without forming secondary phases; however, excessive Mn leads to lattice expansion, structural distortion, and reduced porosity. In contrast, Co-rich compositions exhibit improved crystallinity, well-defined polyhedral morphology, and enhanced pore accessibility, accompanied by a remarkably high specific surface area of up to ۱,۶۶۸.۹ m۲ g-۱. Electrochemical measurements demonstrate that all samples exhibit a hybrid charge storage mechanism combining electric double-layer capacitance and pseudocapacitance. Among them, the Co-rich Co/Mn ZIF-۶۷ (۲:۱) sample delivers the best performance, achieving a high specific capacitance of ۱۵۵ F g-۱ at ۱ A g-۱, superior rate capability, and low internal resistance (Rs ≈ ۸ Ω) and charge transfer resistance (Rct ≈ ۱۰ Ω), indicating efficient ion and electron transport. Additionally, excellent cycling stability with ۱۰۷% capacitance retention after ۵,۰۰۰ cycles highlights its outstanding durability. The enhanced performance is attributed to the synergistic effect between Co and Mn, where a small amount of Mn acts as a structural modulator, improving the coordination environment without compromising framework integrity. This work demonstrates that optimizing metal composition and structural properties is crucial for achieving high-performance metal–organic frameworks (MOFs)-based supercapacitors and provides a promising strategy for designing advanced energy storage materials.

کلیدواژه ها:

Co/Mn ZIF-۶ ، Bimetallic metal-organic frameworks ، Supercapacitor ، Manganese incorporation ، Electrochemical energy storage ، Cycling stability