Prof. Licheng Sun’s group has published their work in the Angewandte Chemie International Edition, highlighting the crucial role of a zwitterion-modified NiFe catalyst that has demonstrated stable performance for over 14000 h at ampere-scale current density in anion exchange membrane water electrolysis device.
Prof. Licheng Sun’s group in the Department of Chemistry at Westlake University recently published a research paper in the Angewandte Chemie International Edition. The paper is titled “Zwitterion-Modified NiFe OER Catalyst Achieving Ultra-Stable Anion Exchange Membrane Water Electrolysis via Dynamic Alkaline Microenvironment Engineering.
Anion exchange membrane water electrolysis (AEM-WE) has emerged as a promising strategy for hydrogen generation, combining the advantages of alkaline water electrolysis (AWE) with low costs and proton exchange membrane water electrolysis (PEM-WE) with high efficiency. However, the oxygen evolution reaction (OER) on the anode in AEM-WE suffers from sluggish kinetics and poor chemical stability hindering its industrial application. In particular, under industrial current densities, rapid accumulation of a large amount of H+ at the anode catalyst surface, coupled with insufficient hydroxide ion (OH−) transport kinetics at the membrane-catalyst interface, leads to a localized decrease in pH, triggering chemical corrosion of the catalyst and significantly deteriorating device performance and long-term stability.
Recently, Prof. Licheng Sun's group at Westlake University developed a zwitterion-modified NiFe-LDH catalyst (z-NiFe) synthesized through simple gradient soaking for highly effective and ultrastable alkaline water oxidation. z-NiFe exhibits a high OER activity (overpotential of 190 mV at 1000 mA cm−2) and stability (over 12600 h at 1000 mA cm−2) in 1 M KOH. Moreover, z-NiFe demonstrates an AEM-WE device activity of 7860 mA cm−2 at a cell voltage of 2.00 V and maintains long-term stability for over 14000 h at 1000 mA cm−2.
In-situ Raman, zeta potential and OH− conductivity data indicate that the presence of zwitterion creates a local alkaline enriched environment around active sites by accelerating OH− transfer from AEM to the catalyst, which can rapidly neutralize the H+ produced during the OER. DFT studies indicate that the O− from the carboxylate group of the z-TCQ ion replaces the lattice oxygen (O2−) between Ni and Fe sites, establishing a local hydrogen bond network that helps stabilize the adsorbed O*.
Our work demonstrates that the zwitterions modulation strategy enables accelerated directional migration of OH− from the membrane and electrolyte to active sites, thereby establishing an alkaline sustained microenvironment at the catalytic interface. The dynamically maintained alkaline microenvironment at the reaction interface spontaneously neutralizes generated H+, effectively suppressing chemical corrosion while enhancing catalytic performance through pH regulation. This strategy offers an in-depth study of the interfacial properties between AEM and catalysts, providing novel insights into the design of anode catalysts and their interactions with membranes.
Dr. Li Wen-Long, Postdoctoral Researcher at Westlake University, Dr. Ding Yun-Xuan, Assistant Researcher at Westlake University, and Dr. Zhao Yi-Long, Postdoctoral Researcher at Westlake University, are co-first authors of the study. The corresponding author is Prof. Licheng Sun, chair professor of chemistry and director of the Center of Artificial Photosynthesis for Solar Fuels at Westlake University.