Green synthesis of non-stoichiometric indium sulfide (In2.77S4) nanoparticles for water splitting and supercapacitance

The synthesis of electroactive multifunctional materials with high performance is an inherently challenging process. Furthermore, finding a green approach to make the process more feasible and convenient is highly desirable. Based on these challenges, herein, a facile and green microwave-assisted approach for the synthesis of phase pure sulfur-deficient indium sulfide (In2.77S4) nanoparticles is demonstrated. Green, economical and readily available reagents, such as castor oil and olive oil, were employed as green dispersants, solvents, and capping agents. Moreover, different sulfur-containing reagents, i.e., sodium sulfide, thioacetamide and thiourea, were employed in the synthesis to elucidate the effect of sulfur source on synthesized nanoparticles. Since electrocatalytic properties are significantly affected by the nature of the ligand on the surface of catalysts, therefore their performance for supercapacitance and water splitting is investigated. High-quality In2.77S4 prepared in castor oil, using thiourea as a sulfur source, showed satisfactory properties for energy storage such as specific capacitance of 540 F/g at 1 A/g current density as well as for both HER and OER with overpotentials of 158 and 346 mV, respectively.