One-Step Synthesis of Selective Nife-Layered Double Hydroxide Anode Catalyst for Highly Efficient and Stable Anion Exchange Membrane Water Electrolyzers, Operating with Seawater

Abstract

Seawater electrolysis faces unique and fundamental chemical challenges, such as the suppression of highly detrimental halogen chemistries [1], that poison the current state-of-the-art anode catalyst and accelerate the degradation of the membrane [2]. The technically favored solution path is to address these issues by developing a new selective catalyst and possibly by limiting operating conditions [3]. Therefore, developing a facile and cost-effective way to design highly active, selective, and and stable seawater-splitting catalysts is of great importance for research and industry [4]. In this work, hexagonal NiFe-layered double hydroxide (LDH) nanosheets were synthesized by one-step solvothermal reactions. As synthesized NiFe-LDH catalyst exhibits high activity, selectivity, and stability towards the oxygen evolution reaction (OER) in alkaline electrolyte, delivering current densities of 10 mA/cm2 at low overpotentials of 359 mV, with no significant degradation observed during RDE testing at constant voltage of 1.57 V for 72 hours in 1.0 M KOH electrolyte. In addition, in order to fabricate catalyst coated electrode (CCE), the nanostructured NiFe-LDH catalyst was homogeneously sprayed onto a platinized titanium porous transport layer (PTL) using an ultrasonic spray coating system. As prepared CCE is used as an anode and commercially available Raney nickel catalyst deposited on a nickel fiber frit is used as a cathode to assemble a MEA with Sustainion® X37-50 grade T anion exchange membrane (AEM) that was tested in alkaline seawater. Employing local seawater, the AEM electrolyzer cell demonstrated stable performance for over 1000 hours at a constant current density of 300 mA cm -2. Reference: [1] S.-C. Ke, R. Chen, G.-H. Chen, X.-L. Ma, Energy Fuels 2021, 35, 12948. [2] S. Dresp, F. Luo, R. Schmack, S. Kühl, M. Gliech, P. Strasser, Energy Environ. Sci. 2016, 9, 2020. [3] S. Dresp, F. Dionigi, S. Loos, J. Ferreira de Araujo, C. Spöri, M. Gliech, H. Dau, P. Strasser, Advanced Energy Materials 2018, 8, 1800338. [4] H. Koshikawa, H. Murase, T. Hayashi, K. Nakajima, H. Mashiko, S. Shiraishi, Y. Tsuji, ACS Catal. 2020, 10, 1886.