In situ Electrochemical Transformation of Ni3S2 and Ni3S2‐Ni from Sheets to Nanodisks: Towards Efficient Electrocatalysis for Hydrogen Evolution Reaction (HER)

Abstract Transition metal sulphides have been viewed as alternatives to platinum based electrocatalysts for HER. Herein, we report the preparation of Ni 3 S 2 in conjunction with Ni in a novel nanosheet morphology and verified its performance for HER. During cyclic polarization, exotic morphological transformation of Ni 3 S 2 ‐Ni from nanosheets to nanodisks has been noted. This change is accompanied with initial increase in over‐potential that passed through maxima (∼ 100mV above the starting potential) and decreased to ∼ 50mV below the starting value. Enhanced electrocatalytic activity due to the morphological changes from sheets to nanodisks has been attributed to the formation of more number of exposed edge‐planes known to promote HER. Kinetic analysis based on Tafel slope displayed by this composite is comparable to that of Pt based catalysts.