Electrospun CoCr7C3-supported C nanofibers: Effective, durable, and chemically stable catalyst for H2 gas generation from ammonia borane

Abstract

Cobalt-chromium carbide-embedded carbon nanofibers (nanocomposite) were prepared via electrospinning of a solution containing cobalt acetate tetrahydrate (CoAc), chromium (II) acetate dimer monohydrate (CrAc), and polyvinylpyrrolidone (PVP) followed by carbonization. Carbonization was achieved at a low temperature (850°C, Ar gas, 6h) as the nanocomposite contained metal carbide. The synthesized nanocomposite was analyzed using advanced analytical techniques. The catalytic activity of the nanocomposite in hydrogen liberation through the hydrolysis of aqueous ammonia borane (AB) solution was evaluated and compared to those of cobalt/carbon nanofibers (Co/CNFs) and cobalt nanoparticles (Co NPs). The synthesized nanocomposite showed the highest catalytic activity at 0.2475mol/min compared to Co/CNFs, 0.174molmin−1, and Co NPs, 0.09molmin−1. The synthesized nanocomposite also showed high stability; it was reused six times without makeup, reactivation, or regeneration. Kinetic studies showed that the rate of AB hydrolysis is dependent on the catalyst concentration and temperature; the value of turn over frequency (TOF) and the activation energy for the prepared nanocomposite were found to be 25.78 molH2 min−1(molmetal−1) and ∼24.2kJmol−1, respectively.