2.2. Synthesis of Diatomite (D)-like KFeS2

The as-prepared FeOOH@D (100 mg), Na₂S·9H₂O (2.88 g), and KOH (19.6 g) were next dispersed and dissolved in 70 mL of the ethanol–water solution (water: ethanol = 1:1). Then, the mixture was transferred into a Teflon-lined stainless-steel autoclave and rotated constantly at 120 °C for 12 h. After cooling to room temperature, the product was washed with DI water and dried at 60 °C for 12 h.