M. Kim, H-S Cho, C. Lee, S. Lee
Korea Institute of Energy Research (KIER),
Keywords: Ni-based electrodes, alkaline water electrolysis, dynamic operation stability
Summary:Due to the accelerating paradigm shift toward renewable energy, water electrolysis systems have been evaluated for their ability to act as long-term renewable energy stores, wherein the energy is stored in the form of hydrogen gas. However, when renewable energy sources are employed, the power provided is intermittent, and so the development of highly active and durable electrode materials that function under these conditions is necessary for the commercialization of water electrolyzers. Compared to other types of electrolysis systems, alkaline water electrolyzers have the advantage of using low-cost electrode materials for the electrochemical water-splitting reactions, wherein the electrochemical oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) occur at the anode and cathode, respectively. Although significant progress has been made in enhancing catalytic activities for both HER and OER using Ni-based electrodes, several studies have recently reported that those Ni-based electrodes undergo irreversible degradation in the dynamic operating environment, thereby leading to issues regarding their stability. In particular, commercial alkaline water electrolyzers directly utilize renewable energy sources, and as a result, the irregular power supply accelerates severe degradation of the Ni-based electrodes due to irreversible surface oxidation, structural defects or collapse of the layered structure. It is therefore desirable to develop durable Ni-based electrodes that exhibit a long-term stability under dynamic operating conditions. Herein, we designed and fabricated Ni-based binary electrodes for alkaline water electrolyzers (porous Ni-Al electrodes for HER, Ni-Fe LDH electrodes for OER), and evaluated their electrochemical performance and under dynamic operating conditions. Importantly, no significant OER & HER performance degradation was observed after the lab-scale dynamic operation tests, and no structural deformation or metal ion dissolution were found to occur. We believe that the findings of this research are therefore attractive whom interested in industrially relevant and cost-effective electrode materials for use in various electrochemical systems.