LAUSR

Abstract Development of abundant and cost-effective electrocatalysts for hydrogen evolution reaction (HER) has gained momentum in recent years. In spite of being one of the largest class of materials, very few metal oxides have shown the propensity for HER in acidic medium. Herein, we report V 10 O 24 .nH 2 O nanofibers as an excellent electrocatalyst material for HER for the first time. We show that V 10 O 24 .nH 2 O nanostructures with a mixed V 5+/ V 4+ oxidation state and a jute-fiber like morphology having a layered disposition and large interlayer spacing of 1.3 nm characterized by interlayer water molecules, can act as an excellent HER electrocatalyst in acidic medium. It required a low overpotential of 118 mV reaching to −10 mA cm −2 current density and at 600 mV overpotential reached a current density of −405 mA cm −2 . It showed excellent durability retaining ca. 90% of its initial activity even after cycling for more than 11 h. Mechanism of the HER electrocatalysis was investigated by Tafel analysis that revealed typical Volmer-Heyrovsky mechanism for the HER with an excellent exchange current density of 1.62 mA cm −2 . The vanadium oxide catalyst was also explored as oxygen reduction reaction electrocatalyst for application in alkaline fuel-cells.