Copper Nanoparticles on Electrospun Carbon Nanofibers as Catalyst for Ullmann Coupling of Iodobenzene

Abstract

In this study, polyacrylonitrile (PAN) nanofiber membranes were fabricated via electrospinning and subsequently carbonized at 2200°C to produce freestanding carbon nanofiber (CNF) substrates. The CNF membrane served as the working electrode in a three-electrode electrochemical system, with a copper sheet counter electrode and Ag/AgCl reference electrode. Copper nanoparticles supported on CNFs (Cu-NPs/CNFs) were synthesized through cyclic voltammetry (CV), where anodic dissolution of the Cu counter electrode generated Cu²⁺ ions, followed by electrochemical reduction and deposition onto CNFs. Crucially, the number of CV scanning cycles (10-15 cycles) was optimized to achieve highly active catalysts. The Cu-NPs/CNFs demonstrated superior catalytic performance in the Ullmann coupling of iodobenzene compared to commercial Cu nanopowder, yielding biphenyl at 85%–89% versus 76.12% for the nanopowder. Material characterization revealed that increasing scan cycles enlarged both the particle density and size of Cu nanoparticles; catalysts prepared with 10-15 cycles exhibited uniform particles with diameters of 30–80 nm. Furthermore, the Cu-NPs/CNFs catalyst maintained structural integrity after 5 reaction cycles, retaining 78% biphenyl yield and demonstrating excellent reusability. This work establishes a controllable electrochemical route for fabricating efficient, separable, and durable carbon-supported metal catalysts.