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Zinc–air batteries (ZABs), which employ oxygen from air for the reduction reaction or discharging, have several benefits, such as high energy density, operational safety, environmental compatibility and low cost. Primary ZABs are a mature technology; however, rechargeable battery design and structure need to be optimized to achieve better cycle life. Two different configurations for a tri-electrode, rechargeable battery with poly(acrylic acid) (PAA) have been developed in this work; i.e., a planar cell and a sandwich cell. Charge-discharge cycling tests at 5 mA-cm–2 show that the sandwich cell is more suitable for ZABs than the planar cell. Various additives for the PAA, such as cross linking agents and ZnO, have also been evaluated using the tri-electrode design. The addition of ZnO to the oxygen reduction reaction side of the battery enhances the cycling performance of ZABs, i.e., the battery can withstand at least 100 cycles at 5 mA cm–2 with initial efficiency of 62%.

Solid state potassium ion selective electrode (K+ ISE) has been the epitome of the most studied chemical sensors in recent years due to its practical importance in biomedical applications. In fact, potassium monitoring in food and serum, urine, and potentially in brain has been carried out in the clinical and medical fields to reveal physical conditions of the patients such as renal diseases, hypopotassemia, alkalosis, cirrhosis of liver, etc. In this report, we developed an electrochemical sensing unit which working, counter and reference electrodes are integrated in a single plane as all-solid-state form. Here, a polyaniline intermediate layer and salt-saturated polyvinylebutyral top coating are introduced in the working and reference electrodes, respectively, in order to mitigate the output potential drift problem that prevented widespread use of solid-state K+ ISE. Morphological and electrochemical properties of K+ ISE are studied by using a scanning electron microscope (SEM) and a potentiostat, respectively. Various measurement modes of electrochemical measurements, including cyclic voltammetry (CV), chronopotentiometry (CP), and electrochemical impedance spectroscopy (EIS), are implemented. The K+ ISE show desirable properties including high sensitivity (60.5 mV/decade), low concentration for the limit of detection (10-5.8 M), and large range of linear detection (10-5 – 1 M). Selectivity of our of K+ ISE against NH4 + , Na+ , Mg2+ , Ca2+ , and Fe3+ was studied. With its high potential to be miniaturized, we foresee that our solid-state K+ ISE will find future applications in microdevices for clinical analysis, agricultural and, environmental applications.