A Comprehensive Survey of Alkaline Electrolyzer Modeling: Electrical Domain and Specific Electrolyte Conductivity

Abstract

Alkaline electrolyzers are the most widespread technology due to their maturity, low cost, and large capacity in generating hydrogen. However, compared to proton exchange membrane (PEM) electrolyzers, they request the use of potassium hydroxide (KOH) or sodium hydroxide (NaOH) since the electrolyte relies on a liquid solution. For this reason, the performances of alkaline electrolyzers are governed by the electrolyte concentration and operating temperature. Due to the growing development of the water electrolysis process based on alkaline electrolyzers to generate green hydrogen from renewable energy sources, the main purpose of this paper is to carry out a comprehensive survey on alkaline electrolyzers, and more specifically about their electrical domain and specific electrolytic conductivity. Besides, this survey will allow emphasizing the remaining key issues from the modeling point of view.

Opportunities of Ionomer Development for Anion-Exchange Membrane Water Electrolysis

“…Ionic transport is achieved by using high concentration (10−30 wt %) KOH/NaOH, with maximum specific conductivity values of 950 mS cm −1 for KOH (50 °C, 30 wt %) and 650 mS cm −1 for NaOH (50 °C, 20 wt %). 9 In order to prevent mixing of the gases, a diaphragm separator is required (Figure 1a). Originally composed of asbestos, modern diaphragms are now fabricated from hydrophilic composites and/or polymeric materials that ensure enough porosity and wettability for efficient ionic transport between the electrodes, but not so high a porosity to allow significant gas crossover, especially if the bubble point differential pressure is exceeded.…”

“…Hydrogen and oxygen evolution reactions were typically carried out on Ni-based plates and mesh electrodes. Ionic transport is achieved by using high concentration (10–30 wt %) KOH/NaOH, with maximum specific conductivity values of 950 mS cm –1 for KOH (50 °C, 30 wt %) and 650 mS cm –1 for NaOH (50 °C, 20 wt %) . In order to prevent mixing of the gases, a diaphragm separator is required (Figure a).…”

Water Splitting Dynamics of High Voltage Pulsed Alkaline Electrolysis

“…Para obtener una mayor producción de hidrógeno, bajo esta ley, es necesario aumentar la cantidad de corriente aplicada a la celda de electrólisis. Si se aumenta el voltaje con este fin, se encuentra un límite relacionado con la eficiencia energética, provocado por el efecto de doble capa capacitivo del agua, además de las pérdidas óhmicas [12], [13], [14]. Si se aplica un voltaje mayor a la tensión reversible, la potencia adicional se verá disipada en forma de calor a causa de las resistencias internas de la celda.…”

Dealloying-Induced Zeolite-like Metal Framework of AB2 Laves Phase Intermetallic Electrocatalysts

“…Such a low market share of electrocatalytic HER is mainly due to the lack of highly efficient and affordable electrocatalysts that operate in the industrial conditions of AWE. In general, it requires the electrocatalyst to carry out HER with a high current density (>400 mA/cm 2 ) in concentrated alkaline electrolyte (>25 wt % KOH, ∼6 M KOH) at elevated temperature (60 °C) . Iron triad-based (i.e., Fe, Co, and Ni) and Pt-based electrocatalysts are the most common cathode materials for AWE owing to their robust corrosion-resistant properties in alkaline electrolyte .…”

“…In general, it requires the electrocatalyst to carry out HER with a high current density (>400 mA/cm 2 ) in concentrated alkaline electrolyte (>25 wt % KOH, ∼6 M KOH) at elevated temperature (60 °C). 5 Iron triad-based (i.e., Fe, Co, and Ni) and Pt-based electrocatalysts are the most common cathode materials for AWE owing to their robust corrosion-resistant properties in alkaline electrolyte. 6 However, the relatively low electrocatalytic activity of HER for an iron triad-based electrocatalyst and the high price of Pt-based electrocatalysts are the critical bottlenecks that impede the wide use of the AWE technique.…”