Orthochannel matrix current collector for high-rate flow electrode capacitive deionization in hypersaline environments

Flow electrode capacitive deionization (FCDI) offers notable advantages, including high adsorption capacity and simplified operation. However, it often suffers from unsatisfactory mass and charge transfer efficiency due to the non-ideal architecture of the current collector. In this study, an orthochannel matrix (OM) current collector was proposed as an advanced design paradigm for the FCDI technology. The orderly arranged and interconnective channels enhanced high-frequency interactions between active substances and the current collector. Additionally, the natural smoothness of graphite minimized interface resistance, thereby significantly enhancing the mass transfer process. As a result, the OM-FCDI device demonstrated superior electrochemical properties, including an exceptionally low charge transfer resistance of 0.13 Ω and a charge percolation resistance of 0.08 Ω. Moreover, compared with the serpentine channel FCDI device, charge leakage of the flow electrode was significantly mitigated, and the specific capacitance of the flow electrode material was enhanced by 52.52 %. During the desalination performance evaluation, an average salt removal rate (ASRR) of 10.42μmol cm⁻² min⁻¹ was achieved using a saline solution containing 1.0 mol L^-1 NaCl, while maintaining a salt removal efficiency (SRE) of 99.86 %. Furthermore, the OM-FCDI device demonstrated remarkable efficacy in desalting natural hypersaline water, achieving over 99.70 % SREs during desalting seawater and salt-lake brine. For the desalination and enrichment of seawater from the South China Sea, the integrated FCDI system achieved water production (WPs) rates exceeding 82.40 % at desalination-to-enrichment module volume ratios ranging from 0.5 to 4.0. The above results further validated the feasibility of the OM-FCDI device for operation under challenging real-world conditions.