Binder-Free Growth of Nickel-Doped Iron Sulfide on Nickel Foam via Electrochemical Deposition for Electrocatalytic Water Splitting

Iron–sulfur-based materials are advantageous for electrocatalytic activity owing to their high natural abundance and lesser toxicity. A few investigations on the hydrogen evolution reaction (HER) catalyzing activity of Fe–S materials were performed. However, the oxygen evolution reaction (OER) catalyzing activity or overall water splitting activity of Fe–S materials has not been studied extensively till date. Another technical aspect that suppresses the activity of the electrocatalyst is related to the usage of polymeric binders for electrode fabrication. Keeping these aspects in mind, iron sulfide was directly electrodeposited on nickel foam by varying the deposition potentials and duration of deposition. Ni-doped O-incorporated iron sulfide having the FeS2 lattice domains was obtained as the deposition product. The morphology, electronic structure, and charge carrier density in the valence band of the electrodeposits changed with the change in duration of electrodeposition, which in turn modulated the electrocatalytic activity. The electrode fabricated at −0.9 V potential after 30 min was found to be superior toward HER and OER. The electrodeposit obtained after 45 min showed comparable HER catalyzing activity. An asymmetric electrolyzer constructed with these electrodes showed a comparable water splitting activity to that of the RuO2(+)||Pt/C(−) electrolyzer and also surpassed its activity at higher potential.