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Green hydrogen production via water electrolysis powered by renewable energy is a critical technology in the pursuit of a net-zero emission economy 1 . Liquid alkaline water electrolyzers (LAWEs), being the most commercially mature electrolyzer technology, play a pivotal role in large-scale green hydrogen production 2 . The utilization of earth-abundant and cost-effective nickel and iron-based materials as cell components of LAWEs reduces capital cost of large-scale electrolyzer cells 3 . However, LAWEs suffer from low operational efficiency, primarily due to low intrinsic activity of unoptimized electrode materials, as well as high ohmic resistance introduced by separators and gas bubbles within thick electrodes. Herein, we used a lab-scale LAWE cell in combination with various electrode configurations to gain a deeper understanding of the limiting factors affecting conventional LAWE performance. Our results show that the electrochemical active surface area (ECSA), chemical compositions, and pore structure of the electrodes are key design parameters to achieve high efficiencies for advanced LAWEs. Besides, particular attention should be paid to the micro-gaps in between electrode and separator, which can be minimized through using electrodes with lower surface porosity and smaller pore size. Consequently, these enabled us to build LAWEs that are capable of sustaining 2 A cm -2 at 2.2 V and operating steadily at 1 A cm -2 for nearly 600 h with negligible performance decay. These findings establish essential criteria for selecting electrodes to achieve high-performance in LAWE and, in turn, expedite the adoption of LAWE technology in green hydrogen production and the transition towards a low-carbon economy. Acknowledgement The authors acknowledge the Department of Energy-Office of Energy Efficiency and Renewable Energy-Hydrogen and Fuel Cell Technologies Office (DOE-EERE-HFTO) and the H 2 from Next-generation Electrolyzers of Water (H2NEW) consortium for funding under Contact Number DE-AC02-05CH11231. References: Pivovar, N. Rustagi and S. Satyapal, The Electrochemical Society Interface, 27, 47 (2018). Ayers, N. Danilovic, R. Ouimet, M. Carmo, B. Pivovar and M. Bornstein, Annual review of chemical and biomolecular engineering, 10, 219 (2019). David, C. Ocampo-Martínez and R. Sánchez-Peña, Journal of Energy Storage, 23, 392 (2019).
Wang et al. (Fri,) studied this question.