Anion Exchange Membrane Water Electrolysis: The Future of Green Hydrogen

Abstract

Hydrogen-derived power is one of the most promising components of a fossil fuel-independent future when deployed with green and renewable primary energy sources. Energy from the sun, wind, waves/tidal, and other emissions-free sources can power water electrolyzers (WEs), devices that can produce green hydrogen without carbon emissions. According to recent International Renewable Energy Agency reports, most WEs employed in the industry are currently alkaline water electrolyzers and proton-exchange membrane water electrolyzers (PEMWEs), with ∼200 and ∼70 years of commercialization history, respectively. The former suffers from inherently limited current densities due to inevitable gas crossover, operates using corrosive (7 M) alkaline solutions, and requires large installation footprints, while the latter requires expensive and scarce precious metal-based electrocatalysts. An emerging technology, the anion-exchange membrane water electrolyzer (AEMWE), seeks to combine the benefits of both into one device while overcoming the limitations of each. AEMWEs afford higher operating current densities and pressures, similar Faradaic efficiencies when compared to PEMWEs (>90%), rapid ramping/load-following responsiveness, and the use of non-noble metal catalysts and pure water feed. While recent reports show promising device performance, close to 3 A/cm 2 for AEMWEs with 1 M KOH or pure water feed, a deeper understanding of the mechanisms that govern device performance and stability is required for the technology to compete and flourish. Herein, we briefly discuss the fundamentals of AEMWEs in terms of device components, catalysts, membranes, and long-term stability/durability. We provide our perspective on where the field is going and offer our opinion on how specific performance and stability tests should be performed to facilitate the development of the field.

Recent progress in understanding the catalyst layer in anion exchange membrane electrolyzers – durability, utilization, and integration

“…Methods for taking polarization curves, impedance spectroscopy, and durability tests should be standardized. Standard metrics for comparing performance (e.g., voltage at 1 A cm À2 , current density at 1.8 V or at a voltage efficiency of 68% 176 ) and durability (e.g., degradation rate in mV h À1 at 1 A cm À2 ) are also necessary.…”

“…Standard metrics for comparing performance ( e.g. , voltage at 1 A cm −2 , current density at 1.8 V or at a voltage efficiency of 68% 176 ) and durability ( e.g. , degradation rate in mV h −1 at 1 A cm −2 ) are also necessary.…”

Application of Ionized Intrinsic Microporous Poly(phenyl-alkane)s as Alkaline Ionomers for Anion Exchange Membrane Water Electrolyzers

“…The production of green hydrogen (H 2 ) via water electrolysis is attracting attention for its potential role and applicability in the large-scale utilization of renewable energy and decarbonization. − Among various water electrolysis technologies, the anion exchange membrane water electrolyzers (AEMWEs) combine the advantages of the low cost of alkaline water electrolyzers and the high efficiency of proton exchange membrane water electrolyzers. − Correspondingly, AEMWEs have shown great potential for commercialization . The membrane electrode assembly (MEA) is the basic unit of an AEMWE and is mainly composed of an anion exchange membrane (AEM), a catalyst layer (CL), and a gas diffusion layer (GDL). , The structural design and components of MEAs directly determine the H 2 output rate and cell efficiency of AEMWEs.…”

Recent progress in anion exchange membranes (AEMs) in water electrolysis: synthesis, physio-chemical analysis, properties, and applications

“…Recent reviews of an AEM focused primarily on fuel cell applications, an electrocatalyst for AEMWE, the technical evaluation of a water electrolysis cell, alkaline water electrolysis for H 2 generation, the economic analysis of H 2 production through electrolyzer technologies, the design of a catalyst and electrode for seawater electrolysis, and the challenges and future opportunities of a component in AEMWE. 27,29,32,45,49,50,55,57,58,150–162 In addition, there are reviews on AEMs such as molecular design and microscopy analysis of membranes for fuel cell and water electrolysis, dealing with alkaline durability of imidazolium-based AEMs, synthesis of ion-exchange membranes for various applications, synthetic approaches for alkaline-stable AEMs, Friedel–Crafts reaction-based synthesis of AEMs for fuel cell and electrolysis applications, click chemistry in AEMs for energy-based applications, the significance of polymer ion exchange membrane structures and properties for hydrogen production by water electrolysis, synthesis of silica-AEMs composite, and anion exchange polyelectrolytes for the synthesis of AEMs and ionomers. 50,88,145,160,163–173 However, no comprehensive review of AEMs from synthesis to application through physiochemical analysis and evaluation of properties has been identified in recent studies.…”