Electrospun Carbon Nanofibers with Embedded Co-Ceria Nanoparticles for Efficient Hydrogen Evolution and Overall Water Splitting

In this study, simple electrospinning combined with pyrolysis were used to fabricate transition-metal-based-nanoparticle-incorporated carbon nanofiber (CNF) electrocatalysts for a high-efficiency hydrogen evolution reaction (HER) and overall water splitting. Co-CeO₂ nanoparticle-incorporated carbon nanofibers (Co-CeO₂@CNF) exhibit an outstanding electrocatalytic HER performance with an overpotential and Tafel slope of 92 mV and 54 mV/dec, respectively. For the counterpart, electrolysis, we incorporate the widely used Ni₂Fe catalyst with a high oxygen evolution reaction (OER) activity into the carbon nanofiber (Ni₂Fe@CNF). To evaluate their electrochemical properties for the overall water splitting, Co-CeO₂@CNF and Ni₂Fe@CNF were used as the HER and OER electrocatalysts in an alkaline electrolyzer. With the paired Co-CeO₂@CNF and Ni₂Fe@CNF electrodes, an overall water splitting current density of 10 mA/cm² was achieved by applying 1.587 V across the electrodes with a remarkably lower overpotential of 257 mV compared to that of an electrolyzer comprised of Pt/C and IrO₂ electrodes (400 mV). Owing to the conformal incorporation of nanoparticles into the CNF, the electrocatalysts exhibit significant long-term durability over 70 h of overall water splitting. This study provides rational designs of catalysts with high electrochemical catalytic activity and durability to achieve overall water splitting.