(Digital Presentation) Novel Layered Materials with Rapid Ion Transport for Capacitive Deionization

Abstract

Capacitive deionization is a very promising method for future water desalination. However, desalination capacity and rate limit its wide application. In our study, layered carbon materials and layered double hydroxides with rapid ion transport were investigated to overcome the rate issue. A layered activated carbon was synthesized by carbonizing and activating chestnut inner shell and the biochar showed lamellar structure and high specific surface area (>1000 m2 g-1). The one obtained at 500 ℃ (CS500) exhibited the highest specific surface area (1943.2 m2 g-1) and more oxygen-containing functional groups. Correspondingly, CS500 achieved a significant average salt adsorption rate of 5.7 mg g-1 min-1, with a high salt adsorption capacity of 17.7 mg g-1 NaCl (0.5 g L-1). CS500 also maintained high cycle stability (87.0%, 1.2 V) within 50 adsorption/desorption cycles. Besides, CoAl-layered metal oxide nanosheet intercalated by sodium dodecyl sulfate (SDS) with enhanced interlayer spacing (1.33 nm) was synthesized and used as anode (CoAl-LMO-SDS). The enlarged interlayer spacing and heat treatment provided an enhanced ion diffusion channel, improved the utilization of the interlayer electroactive sites and offered additional active oxidation reaction sites to facilitate the electro-sorption rate. CoAl-LMO-SDS achieved a high salt adsorption capacity (31.78 mg g-1), average salt adsorption rate (3.75 mg g-1 min-1) at 1.2 V in 500 mg L-1 NaCl solution, and excellent long-term cycling stability (92.9%) after 40 CDI cycles, proving the strong electronic interaction between SDS and the host layer. The desalination performance significantly show that layered materials can be promising candidates for rapid desalination and large-scale application.