Synergistic Effects of Metal-Modified Carbon Nanotubes: Experimental Characterization and Theoretical Modeling for Energy and Environmental Solutions

Abstract

Metal-functionalized carbon nanotubes (CNTs) have emerged as versatile nanostructures with tunable properties for energy conversion, storage, and environmental remediation. In this study, we integrate experimental investigations with theoretical modeling to explore the structureproperty relationships and multifunctional performance of CNTs decorated with transition metal nanoparticles (Ni, Cu, Ag) and their synergistic combinations (Ni-Cu-Ag). A scalable and facile synthesis route was employed to fabricate these nanocomposites, which were thoroughly characterized to evaluate their structural, morphological, optical, and surface chemical features. The metal-functionalized CNTs demonstrated significant enhancements in oxygen evolution reaction (OER) activity, capacitive energy storage, and photocatalytic degradation of organic pollutants. Notably, the ternary CNT-Ni-Cu-Ag nanocomposite exhibited outstanding OER performance with an overpotential of 382 mV at 50 mA cm⁻² and a Tafel slope of 73 mV dec⁻¹, along with a high specific capacitance of 1451 F g⁻¹ and excellent stability (98% retention after 5000 cycles). Furthermore, the material achieved remarkable photocatalytic degradation efficiencies of Ciprofloxacin (98.5%) and Diclofenac sodium salt (86%) within 120 minutes under visible light. Complementary density functional theory (DFT) simulations revealed the preferential adsorption of metal nanoparticles on the CNT surface and their role in modulating the electronic band structure, thereby rationalizing the enhanced catalytic and optoelectronic behavior. These results highlight the promise of metalfunctionalized CNTs as multifunctional platforms for next-generation energy conversion, storage, and environmental remediation technologies.