Activity Evaluation of Co/Zn-NC@PPy-۸۰۰ as a Non-noble ORR Catalyst in Fuel Cell-based Breath ethanol sensor

The oxygen reduction reaction (ORR) plays a leading role in electrochemistry. The ORR is one of the most challenging issues in many types of electrochemical instruments such as Lithium-air batteries and fuel cell-based breath alcohol sensor (BrAS). The challenge is the slow ORR kinetics and its essential need for Pt-based catalysts; These issues have led to attempt to substitute Pt-based catalysts with nonprecious metal catalysts (NPCs). In this work, Co/Zn-NC@PPy-۸۰۰ is used as an ORR catalyst. According to the Fig. ۱, the nanostructure of Co/Zn-NC@PPy-۸۰۰ is made up of approximately equally formed N-doped sheet-like carbon (Fig.۱a). The cell performance evaluation is depicted in Fig. ۲. The cell is made of ۶۰ wt. % Pt/C with loading of ۱۰ mg. 𝑐𝑚−۲ and Co/Zn-NC@PPy-۸۰۰ with loading of ۲ mg. 𝑐𝑚−۲ as anode and cathode electrocatalysts, respectively. The anion-exchange membrane (A۲۰۱ Tokuyama), with a thickness of ۲۸ μm is used as electrolyte. The fuel is fed using various concentrations of ۳ mM – ۵۰ mM of ethanol in a ۲ M KOH solution. The cell polarization curves (Fig. ۲a) demonstrate that with decreasing in ethanol concentration, decreasing in current and power density will occur. This behavior exhibits changing of response against changing of concentration and it is suitable for alcohol sensor applications. Electrochemical impedance spectroscopy (EIS) experiments represent increasing the diameters of semicircles with decreasing in the concentration of ethanol (Fig. ۲b). Cathode and anode polarizations are displayed in Fig. ۲c and Fig. ۲d respectively and it can be found that cathode polarization is constant in various concentrations of ethanol, which means changing ethanol concentrations do not affect cathode polarization. In contrast, anode polarization has a direct relation to ethanol concentration and lower fuel concentration lead to more anode polarization due to more fuel mass transfer limitation.