Bifunctional Potential Structure Design Breaks Electrolyte Limitations of Zinc Ion Battery

Aqueous zinc-ion batteries (ZIBs) are safe and economical for grid applications. However, current ZIBs have limitations in terms of inferior capacity and low output voltage, which are hampered by the electrolyte applicability of the Zn2+ hosts. In this study, we propose a novel organic cathode design strategy with a bifunctional potential region. This polymeric Zn2+ host combines the conjugated polyaniline backbone to tune the molecular surface pH and [Fe(CN)6]3-/4- redox couple for high output voltage and capacity. The polyaniline doped with ferricyanide (PAF) electrode exhibits two forms of charge storage in ZIBs: proton-assisted Zn2+ doping below 1.2 V (mechanism I), and [Fe(CN)6]3-/4- redox pair above 1.8 V (mechanism II). Density functional theory calculations and in situ pH experiments demonstrated that the H+ doping process of mechanism I forms a localized pH regulation on the molecular chain surface, providing a favorable reaction environment for mechanism II. The Zn-polymer battery delivered an outstanding discharge capacity (405.2 mAh g-1) and high output voltage (1.8 V) in the Zn(CF3SO3)2 electrolyte. This study provides a new route for enhancing the structural stability of electrodes and overcoming the electrolyte limitations of ferricyanide in weakly acidic electrolytes.

Amyloid Beta Detection by Faradaic Electrochemical Impedance Spectroscopy Using Interdigitated Microelectrodes

Faradaic electrochemical impedance spectroscopy (f-EIS) in the presence of redox reagent, e.g., [Fe(CN)₆]3-/4-, is widely used in biosensors owing to its high sensitivity. However, in sensors detecting amyloid beta (Aβ), the redox reagent can cause the aggregation of Aβ, which is a disturbance factor in accurate detection. Here, we propose an interdigitated microelectrode (IME) based f-EIS technique that can alleviate the aggregation of Aβ and achieve high sensitivity by buffer control. The proposed method was verified by analyzing three different EIS-based sensors: non-faradaic EIS (nf-EIS), f-EIS, and the proposed f-EIS with buffer control. We analyzed the equivalent circuits of nf-EIS and f-EIS sensors. The dominant factors of sensitivity were analyzed, and the impedance change rates via Aβ reaction was compared. We measured the sensitivity of the IME sensors based on nf-EIS, f-EIS, and the proposed f-EIS. The results demonstrate that the proposed EIS-based IME sensor can detect Aβ with a sensitivity of 7.40-fold and 10.93-fold higher than the nf-EIS and the f-EIS sensors, respectively.