Nanoconfined Water Manipulated Selective Proton Storage in Layered Tungsten Oxides for Versatile Supercapacitor Diodes

Supercapacitor diode (CAPode) is an emerging type of electrochemical logic device that integrates ions and electrons as the coinformation carriers, thus being a promising building block for constructing new-type iontronic circuits and achieving seamless brain-computer interaction. However, the lack of understanding on its basic process, i.e., nanoconfined ion transport, greatly blocks the further enhancement of its ion rectification capability and ion transport kinetics. Herein, on the basis of in-depth analysis of the host-guest interactions in the nanoconfined space, a nanoconfined water mediated strategy is proposed to manipulate the ion transport behaviors in typical layered materials, i.e., tungsten oxides (WO₃·<i>n</i>H₂O, <i>n</i> = 0, 1, 2). The results reveal that WO₃·H₂O presents an optimal ion rectification capability and superior ion transport kinetics, much outperforming those of WO₃·2H₂O or WO₃ with more or less structural water. Consequently, the WO₃·H₂O-based CAPode delivers a record-high rectification ratio of 253, an ultrahigh response frequency of 549 Hz, and an excellent cycling stability of up to 5000 cycles, enabling it to handle various complex ion/electron-coupling logic operations. More attractively, WO₃·H₂O is demonstrated to possess superior biocompatibility, endowing the as-built CAPode with great potential in the cutting-edge field of brain-computer interactions.