Sodium sulfate na2so4

Acetic acid (>99.5%) was purchased from Titan. Sodium hydroxide (NaOH, >96.0%), acetylacetone (99%), and sodium sulfate (Na₂SO₄, >99.0%) were purchased from Sinopharm Chemical Reagent. Iron(III) acetylacetonate (>98%) was purchased from Shaoyuan. Titanium butoxide (≥99%) was purchased from Macklin. Fluorine‐doped tin oxide (FTO, resistance < 15 Ω sq⁻¹, transmittance >83%) substrates were purchased from Kaivo Optoelectronic Technology.

As the raw material, the digested sludge was collected from the anaerobic digestion reactor of our laboratory [18 (link)] and was stored at −80°C before use. Acetylene black was purchased from Cabot Co., USA. Polytetrafluoroethylene (PTFE) solution (60% suspension in water) was purchased from Aladdin Chemistry Co., Ltd. Potassium hydroxide, hydrochloric acid, hydrofluoric acid and sodium sulfate (Na₂SO₄) were of analytical grade and purchased from Sinopharm Chemical Reagent Co., Ltd. All reagents used in this work were used as received without any further purification. Ultrapure water for solution preparation was supplied from a water purification system (Hitech Instrument Co., Shanghai, China).

Graphite powers were purchased from Alfa Aesar and waste fiberboard materials were used to product ACs. Sodium nitrate (NaNO₃), sulfuric acid (H₂SO₄), potassium permanganate (KMnO₄), hydrochloric acid (HCl), manganese(II) acetate tetrahydrate [Mn(CH₃COO)₂·4H₂O] and sodium sulfate (Na₂SO₄) were obtained from Sinopharm Chemical Reagent Co., Ltd (Beijing, China). All chemicals were used as received without further purification.