Modulation of Chloride Storage Behavior by Interfacial Coupling for Stable Capacitive Deionization.

In capacitive deionization (CDI), the practical deployment of high-capacity Faradaic electrodes for chloride capture is fundamentally constrained by their structural instability. Here, we overcome this limitation by constructing an interfacial-coupled heterostructure of BiOCl with nitrogen-doped carbon (NC). Beyond serving as a conductive scaffold, the NC substrate fundamentally redirects the chloride (de)intercalation pathway, shifting it from an incessant phase transformation between BiOCl and Bi to a highly reversible process governed by the formation and healing of chlorine vacancies (VCl), which is complemented by adsorption at N sites. This mechanistic switch ensures exceptional cyclic integrity. Consequently, the BiOCl@NC electrode not only achieves a remarkable Cl- adsorption capacity of 175.23 mg g-1 but also exhibits excellent cycling stability with 88.03% capacity retention over 100 cycles. This work redefines the stability mechanism of bismuth based electrodes and establishes a general design principle for durable Faradaic materials in sustainable desalination.