UNRAVELING THE INTERMOLECULAR ELECTRON TRANSFER OF POROUS CARBON NANOFIBERS DERIVED FROM COTTON WASTES VIA INTERFACIAL HETEROATOMS DEFECTS FOR GREEN HYDROGEN PRODUCTION

Abstract

Rational design of efficient electrocatalysts for hydrogen evolution reaction (HER) has sparked the global attention to decrease the cost of green hydrogen production, however it remains challenged. In this thesis, we unravel the simple, green, and one-pot method for the scalable design of ultra-long (1-3 mm) carbon fiber (p-CFs) from cotton fiber biomass wastes atomically functionalized with heteroatoms (HAs) at the atomic level (HAs/p-CFs) (HAs= O, B, P, N, and F) by immersion and carbonization method at relatively low temperature. The interaction between electronegative HAs and CFs led to an optimal intermolecular charge transfer process giving rise to efficient electrocatalyst with rich active sites; however O/p-CFs was the optimum. The HER activity followed the trend of O/p-CFs >B/h-CNF > P/p-CFs >N/p-CFs >F/h-CNF>p-CFs. The HER current density reached 325 mA/cm2 on O/p-CFs with a low overpotential at 10 mAcm2 (ƞ10) of -0.3 V, and H2 production rate of 109 mol· gmetal-1·h-1. The HER activity of O/p-CFs was close to Pt/C, and it was among highest reported carbon-based electrocatalysts besides ease of preparation method. This is due to unique structural merits and atomic distribution of O-atom that generate rich interfacial structural defects within CFs framework, and endowing the intermolecular electron transfer at O/p-CFs interfaces results in efficient HER. These findings may pave the way for engineering of biomass wastes with other HAs for green HER.