Journal Article

PUBDB-2026-00495

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Beyond global metrics in capacitive water deionization: Position-resolved ion concentration from operando X-ray transmission

Rauscher, M. V.Extern* ; Kohns, R. (Corresponding author)Extern* ; Seyffertitz, M.Extern* ; Stock, S. ; Haas, S.DESY* ; Presser, V. ; Prehal, C.Extern* ; Hüsing, N. ; Paris, O. (Corresponding author)Extern*

2026
Elsevier Science Amsterdam [u.a.]

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Please use a persistent id in citations: doi:10.1016/j.desal.2026.119849  doi:10.3204/PUBDB-2026-00495

Abstract: The performance of novel electrode materials and the influence of cell geometry or flow rate on capacitive water deionization (CDI) are usually described by global metrics from the analysis of the effluent electrolyte together with the electrochemical response of the system. However, these approaches cannot provide information on local variations of ion concentration and related local efficiency within an operating device. Here, a novel approach of position-resolved operando synchrotron-based X-ray transmission is introduced to determine local ion concentration changes along the flow channel from the inlet (feedwater) to the outlet (effluent water) of a working CDI cell. A specific cell design allows the independent quantification of concentration changes within the bulk electrolyte in the flow channel as well as the two oppositely charged nanoporous electrodes. Results from a 15 mM CsCl feed solution using three flow rates and two carbon materials with hierarchical porosity reveal a complex spatial- and temporal ion distribution in the system. A distinct dependence of local concentration on the flow rate is observed, with generally decreasing local desalination capacity towards the outlet of the cell, particularly for slow flow rates. It is also found that a significantly better overall performance for one of the two materials can be related to dominant counter-ion adsorption within ultramicropores, which ions cannot access in their hydrated state at no applied potential (ionophobicity). Overall, the results demonstrate the unique potential of position-resolved operando X-ray techniques to get mechanistic insight into local ion redistribution in CDI systems, allowing ultimately guiding performance optimization.

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Contributing Institute(s):

1. CIMMS-RA Center for integr. Multiscale M (CIMMS)

Research Program(s):

1. 632 - Materials – Quantum, Complex and Functional Materials (POF4-632) (POF4-632)
2. FS-Proposal: T-20240163 EC (T-20240163-EC) (T-20240163-EC)

Experiment(s):

1. PETRA Beamline P62 (PETRA III)

Appears in the scientific report 2026

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Database coverage:
; ; ; Clarivate Analytics Master Journal List ; Current Contents - Engineering, Computing and Technology ; Ebsco Academic Search ; Essential Science Indicators ; IF >= 5 ; JCR ; SCOPUS ; Science Citation Index Expanded ; Web of Science Core Collection

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