Polyacrylamide hydrogel-derived three-dimensional hierarchical porous N,S co-doped carbon frameworks for electrochemical capacitors

Abstract

Cost-effective porous carbon materials have been widely used in advanced electrochemical capacitors (ECs). Herein, we developed a simple yet scalable method to fabricate a porous hierarchical N,S co-doped carbon framework (HNSC-F) using a polyacrylamide hydrogel (PAAG) soaked with CH₄N₂S as a precursor. The HNSC-F is endowed with a large surface area of ∼1192.1 m² g⁻¹, microporosity of ∼91.8%, high surface wettability, and a high O content of ∼8.4 at%, N ∼ 5.3 at% and S ∼ 0.8 at%. When evaluated as an electroactive material for ESs, the resulting HNSC-F electrode with a loading of 5 mg cm⁻² delivers a specific capacitance (SC) of ∼254.4 F g⁻¹ in 6 M KOH, and even ∼325.8 F g⁻¹ at 1 M H₂SO₄ at 0.5 A g⁻¹, owing to the extra heteroatom-involved faradaic reaction. Furthermore, the HNSC-F-based symmetric device with 6 M KOH exhibits a high energy density of ∼10.3 W h kg⁻¹ at ∼325.0 W kg⁻¹ within an operating window of an upper voltage limit of 1.3 V. Moreover, the symmetric ECs exhibit excellent SC retention with both alkaline (∼102.3%) and acidic (∼96.5%) electrolytes even after 5000 consecutive cycles. This promises the HNSC-F as a competitive electrode for advanced ECs.