Enhanced hydrogen evolution activities of the hollow surface-oxidized cobalt phosphide nanofiber electrocatalysts in alkaline media

For green-hydrogen production through a promising electrolytic water splitting, cobalt phosphide is in the spotlight as one of the new affordable materials to replace currently used noble-metal catalysts. In this study, we fabricate hollow cobalt phosphide (CoP) nanofibers with advanced nanostructure using electrospinning and phosphidation. Due to their unique architecture and oxygen-rich surface characteristics, the novel hollow-structure CoP nanofibers effectively increase hydrogen evolution reaction catalytic activity with the low overpotentials of 91 mV (for acid) and 63 mV (for alkaline). Using in situ Raman spectroscopy, it is confirmed that high-oxygen-containing CoP catalysts could transform the CoOOH phase under alkaline conditions, which offer faster water dissociation kinetics. Furthermore, CoP nanofibers exhibited excellent durability even after 30000th accelerated degradation test cycles and overall water splitting for 40 h.