The research on cost-effective approaches for the electrode in proton exchange membrane water electrolyzer

Abstract

In addition to serious environmental pollution problems, the lack of fossil fuels has become a major problem in modern society. Therefore, clean carrier hydrogen has attracted as an important method as a new eco-friendly energy source that can solve this problem. Among the methods of producing such eco-friendly hydrogen, polymer electrolyte membrane water electrolysis (PEMWE), which is capable of producing 100% pure hydrogen without environmental pollution, has been extensively studied. In the PEMWE method, both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) occur simultaneously. Since the OER is slower than HER and occurs at high voltage, expensive noble metal catalysts are used to operate the system. Additionally, since the price of the entire water electrolysis system is high, many studies are being conducted to reduce it. Therefore, in this study, the research to reduce the overall price of the PEMWE system is divided into two parts. In the first part, by utilizing a metal oxide support (Ti4O7), an OER catalyst with a good balance of performance, durability, and corrosion resistance was synthesized with less amount of iridium. As a result of comparing the performance of supported catalysts with various ratios by half-cell evaluation, the IrOx/Ti4O7(7:3) catalysts showed the highest mass activity with 372 ± 15.1 mA mg-1 at 1.55 V, followed by the IrOx/None catalyst with the mass activity of 353 ± 11.4 mA mg-1. Also, the MEA performance of IrOx/Ti4O7(7:3) showed 139% compared to the unsupported catalyst based on the same amount of iridium. Through this, the price of the electrode can be reduced by using Ti4O7 support. In the second part, a new electrode fabrication method was presented by introducing a new polymer binder, hydroxypropyl methylcellulose (HPMC), into the electrode. When evaluating the interfacial stability of the electrode using the HPMC, it was found that the electrode shape was maintained for 24 hours without any peeling. Furthermore, Nafion® and HPMC electrodes showed similar performance with 1.60 ~ 1.61 V at 2 A cm-2. In addition, in the subsequent 72-hour durability test, it was confirmed that each electrode showed a low degradation (less than 0.3 mV h-1). Through this, HPMC, which is about 80 times cheaper than Nafion®, can be used instead of Nafion®, and the electrode manufacturing price included in the GW-scale can be reduced. Although the degree of activity degradation is still slightly larger than that of Nafion® after durability, it seems that through an additional electrode optimization process, a more advanced electrode can be manufactured at a sufficiently lower price.