Tailoring the bifunctional electrocatalytic activity of electrodeposited molybdenum sulfide/iron oxide heterostructure to achieve excellent overall water splitting

Abstract

• MoS 2 /Fe 2 O 3 heterostructure was fabricated by facile two-step electrodeposition. • Alteration in duration of the deposition steps regulated the water splitting efficiency. • Substrate adsorption–desorption and charge transfer efficiency of the heterostructure varied with deposition duration. • Tailored MoS 2 /Fe 2 O 3 heterostructure outperformed water splitting activity of the state-of-the-art RuO 2 || Pt/C electrolyzer. Development of facile strategies to directly fabricate the noble-metal-free heterostructure on the conducting substrate and tailoring its electrocatalytic activity are crucial to achieve the superior overall water splitting activity. Herein, a series of MoS 2 /Fe 2 O 3 heterostructure was directly fabricated on nickel foam substrate by a facile two-step electrodeposition technique. The alteration in duration of the deposition steps regulated the physicochemical properties and water splitting efficiency of the resulting heterostructure. A correlative investigation of Tafel and Nyquist plot revealed that the substrate adsorption–desorption and charge transfer efficiency of the heterostructure varied owing to this alteration. The successful integration of Fe 2 O 3 with MoS 2 synergistically enhanced the electrocatalytic activity of the heterostructure and binder-free growth on conducting nickel foam (NF) helped it to achieve higher catalytic current density. The heterostructure obtained through 5 and 6 min long two-step electrodepositions (F5M6), showed superior bifunctional electrocatalytic activity. The symmetric cell constructed with F5M6 electrode outperformed the state-of-the-art RuO 2 || Pt/C electrolyzer at higher operating voltage region and was able to achieve a current density of 757 mA cm −2 at 2 V. Moreover, the heterostructure could sustain its overall water splitting proficiency for ~ 30 h at high current density confirming its excellent overall water splitting efficacy. This investigation established the two-step electrodeposition process as an effective electrocatalytic-activity-tailoring strategy.