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Highly Efficient Water Electrolysis Using NaOH–KOH Hydrate Melt (Supporting Information)

Version 2 2024-04-03, 00:20
Version 1 2024-03-07, 00:50
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posted on 2024-04-03, 00:20 authored by Keita GOTO, Kenji KAWAGUCHI, Toshiyuki NOHIRA
To enhance the efficiency of water electrolysis, this study focuses on the NaOH–KOH hydrate melt (NaOH : KOH : H2O = 9 : 61 : 30 mol%) at temperatures ranging from 100 to 200 °C. We examined the behaviors of hydrogen and oxygen evolution reactions (HER and OER) on a Ni electrode at atmospheric pressure. In the Tafel plots, the upper limit of the Tafel region for both HER and OER expanded with increasing temperature, especially at 200 °C. Additionally, changes in the rate-determining step for HER and OER were observed compared to a 30 wt% KOH aqueous solution at 80 °C. The total overpotential for HER and OER was compared to the value of 1133 mV obtained in the 30 wt% KOH aqueous solution (80 °C, 500 mA cm−2). The total overpotentials in the NaOH–KOH hydrate melt at 200 °C and 500, 1000, and 2000 mA cm−2 were 545, 619, and 714 mV, respectively. The reduction in overpotentials was 52 %, 45 %, and 39 %, respectively. Water electrolysis utilizing the NaOH–KOH hydrate melt shows promising potential for significantly enhancing energy efficiency even at higher current densities relative to traditional alkaline water electrolysis.

Funding

Japan Science and Technology Agency

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Corresponding author email address

kawaguchi.kenji.6a@kyoto-u.ac.jp

Copyright

© 2024 The Author(s).

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