Understanding the Co : Mo Compositional Modulation and Fe‐Interplay in Multicomponent Sulfide Electrocatalysts for Oxygen and Hydrogen Evolution Reactions

Amidst the escalating urge in the economical generation of clean hydrogen fuel from water, this article presents the development of simple and economical electrocatalysts, Cobalt Molybdenum Sulfides (Co−Mo−S), for oxygen evolution (OER) and hydrogen evolution (HER) reactions. The compositional modulation of Co and Mo produces the highly active catalysts, Co 0.75 Mo 0.25 S x for OER and Co 0.40 Mo 0.60 S x for HER. Moreover, the potentiality of Fe incorporation in CoMoS x is demonstrated in enhancing the OER performance of the catalyst. The best catalyst for OER (Fe 0.05 Co 0.70 Mo 0.25 S x ) achieves a current of 10 mA cm −2 at an overpotential (η 10 ) of 227 mV (1.457 V vs RHE) while that for HER (Co 0.40 Mo 0.60 S x ) requires only 130 mV (−0.13 V vs. RHE) of η 10 . The holistic enhancement of the OER kinetics is attributed to the facile generation of CoOOH in the co‐existence of Fe at oxidation states≥+3, and Mo at +6 and +5 states. Finally, a complete water electrolyser is demonstrated using Fe 0.05 Co 0.70 Mo 0.25 S x as the anode and Co 0.40 Mo 0.60 S x as the cathode.