Rational fabrication of metal phosphide nanoparticles immobilized in electrospun carbon nanofibers for efficient pH-universal hydrogen evolution and overall water splitting

Design and preparation of bifunctional electrocatalysts with optimized structures and abundant electrocatalytic active sites are significant for hydrogen generation in electrocatalytic water splitting. Herein, we have elaborately prepared Fe-doped CoP nanoparticles encapsulated in porous electrospun carbon nanofibers for bifunctional electrocatalysis on both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The morphologies, components, and properties of the prepared electrocatalysts are influenced by the introduction of a facile air calcination treatment. Porous nanostructure as well as the full conversion of metal active sites are simultaneously achieved. Owing to the protective electrospun carbon nanofibers as well as the abundant exposed active sites, the optimized electrocatalyst exhibits excellent pH-universal HER activities with small overpotentials (99 mV, 159 mV, and 185 mV) at 10 mA cm−2 in acidic, alkaline, and neutral electrolytes, and also presents remarkable OER performance. Moreover, a water electrolyzer cell, using the optimized electrocatalyst as the electrodes, manifests both a high efficiency (1.63 V@10 mA cm−2) and robust stability. This work provides a convenient route for the controllable fabrication of transition metal-based electrocatalysts toward energy conversion.