Influence of Phosphidation on CoSe2 Catalyst for Hydrogen Evolution Reaction

The development of highly active and earth‐abundant electrocatalyst for the hydrogen evolution reaction (HER) is essential for hydrogen based energy technologies. Recently, cobalt chalcogenides and phosphides have been extensively investigated as a promising class of non‐precious electrocatalyst for HER because of its high catalytic activity. Here, we have grown a novel and efficient cobalt selenide|cobalt phosphide (CoSe2|CoP) based HER catalyst on carbon fiber paper (CFP) through a facile conversion of CoSe2 nanostructures into a hybrid CoSe2|CoP by phosphidation. Phosphorus compositions in the CoSe2|CoP nanosheets are controllable by adjusting the time duration of phosphidation viz., 15, 30 and 60 min. The catalyst CoSe2|CoP/CFP in acidic media at 30 min showed higher catalytic activity with low overpotential (η) of 140 mV at 10 mA/cm2 and a Tafel slope of 42 mV/dec than parent CoSe2/CFP (η ‐ 219 mV at 10 mA/cm2; Tafel slope ‐ 44 mV/dec) and CoP/CFP (η ‐ 168 mV at 10 mA/cm2; Tafel slope ‐ 86 mV/dec). The improved HER activity of CoSe2|CoP is attributed to the formation of the hybrid nanosheets and the synergistic effect between CoP and CoSe2. Moreover, the surface morphology of CoSe2|CoP at 30 min catalyst plays a significant role in electron transportation. Thus, the present work opens a new potential way to design and develop novel hybrid HER electrocatalysts based on CoSe2|CoP as an efficient energy conversion system through their composition and structural morphology. CoSe2|CoP/CFP after 30 min of phosphidation displays a characteristic flower like and thin nanosheets structures and the resulting structural changes emphasize the significant role of phosphorus to obtain a catalyst with superior electrochemical properties and fast charge transfer kinetics. The time dependent (15 min, 30 min, and 60 min) phosphidation process has a significant impact on the morphological changes and catalytic activity.