Research Background
Hydrogen energy is vital for renewable energy storage and "dual carbon" goals, but 95% of global hydrogen production relies on fossil fuel reforming (emitting ~1.3 billion tons of CO₂ yearly), driving demand for green hydrogen via water electrolysis. Anion exchange membrane water electrolysis (AEMWE) combines the advantages of alkaline water electrolysis (noble-metal-free, low cost) and proton exchange membrane water electrolysis (high current density, compact structure), but its industrialization is limited by traditional membrane electrode assemblies (MEAs). Disordered component stacking in traditional MEAs causes discontinuous mass transport channels and fragmented triple-phase interfaces, restricting high-current-density performance—making ordered membrane electrode construction a core breakthrough direction.
Research Progress
While the team acknowledges that component-level optimization (e.g., developing transition metal-based catalysts for catalyst layers, balancing conductivity-stability for anion exchange membranes, and designing hierarchical pores for gas diffusion layers) and interface engineering (e.g., regulating ionomer content to reduce interfacial contact resistance to <10 mΩ·cm²) lay the foundation for MEA performance, the focus of their review is on the construction of ordered membrane electrodes—a transformative approach to address high-current-density operation challenges. Traditional MEAs suffer from disordered distribution of OH⁻, electrons, gas, and water, leading to significant polarization that restricts high-current performance; even binder-free self-supporting electrodes face interfacial resistance due to poor catalyst layer (CL)-anion exchange membrane (AEM) contact. To resolve this, the team summarized three concise advanced strategies for gap-free, ordered MEAs, all targeting seamless CL-AEM contact and ordered transport channels to meet industrial current density requirements (>1 A/cm²).
The first strategy is nanoimprinting and template-assisted fabrication, which uses templates like anodic aluminum oxide (AAO) to build ordered ion channels. It boosts the electrochemically active area by up to 8.7-fold (vs. conventional MEAs), cuts mass transport overpotential by 13.9%, and lowers catalyst loading to 20.0 μg/cm², but is limited to lab scale due to fragile templates and complex alignment for large-area production.
The second strategy is integrated membrane electrodes, which grow catalysts in-situ within porous membranes via solvothermal synthesis to form seamless CL-AEM interfaces. It achieves 1000 mA/cm² at 1.57 V (94% energy efficiency) and maintains stability for >1000 hours at 1000 mA/cm² (60 °C), yet scaling beyond 100 cm² is challenging due to strict solvothermal synthesis constraints.
The third and most industrially promising strategy is 3D interlocked interfaces, which uses ultrasonic spraying to deposit AEM onto preformed CLs— eliminating hot-pressing and enabling perpendicular alignment of electron transport channels and AEM. It delivers exceptional performance: up to 4200 mA/cm² at 2.0 V (1 M KOH) and 1800 hours of stability at 1.0 A/cm² (pure water), while reducing overall cell resistance by 40%. Though it balances durability and scalability, it faces challenges like high ultrasonic spraying equipment costs and difficulty controlling ionomer distribution in 3D pores.
Future Outlook
The team points out that while ordered membrane electrodes have shown great potential, three key challenges remain for industrial application. First, standardized evaluation systems for ordered MEAs are lacking— current testing conditions (e.g., current density, electrolyte concentration) vary widely, hindering performance benchmarking. Future efforts should establish industrial scenario-based standards, such as minimum stability requirements (>1000 hours, voltage decay <2 mV/h). Second, multiscale mechanism research is needed to clarify the long-term stability of ordered structures, such as how ionomer distribution in 3D pores affects degradation under humid-heat conditions. Finally, scalable manufacturing technologies are critical: lab-scale methods like template-assisted electrodeposition are low-yield and equipment-intensive, so future work should focus on roll-to-roll ultrasonic spraying optimized by AI (to improve coating uniformity to >95%) and template-free ordered structure preparation, aiming to reduce green hydrogen production costs below $1.5/kg.
Sources: https://spj.science.org/doi/10.34133/research.0907
