A comprehensive review on atomic layer deposition on key components in fuel cells

Atomic Layer Deposition (ALD) has emerged as a cutting-edge nanofabrication technique for enhancing the performance, durability, and efficiency of fuel cells by enabling atomic-scale precision in material deposition. This review critically evaluates the role of ALD in optimizing key fuel cell components, including electrolytes, electrodes, and balance-of-stack (BoS) elements, such as interconnects, bipolar plates, and gas diffusion layers (GDLs). ALD facilitates the development of ultrathin, conformal, and defect-free coatings, addressing major challenges such as catalyst degradation, mass transport limitations, high ohmic resistance, and material instability. In solid oxide fuel cells (SOFCs), ALD has been instrumental in stabilizing perovskite cathodes, mitigating strontium segregation, and enhancing oxygen reduction reaction (ORR) kinetics, leading to a 2.7-fold increase in power density at intermediate temperatures. In protonic ceramic fuel cells (PCFCs), ALD-engineered nanostructured cathodes and proton-conducting electrolytes have demonstrated improved proton transport efficiency and extended operational lifetimes. For polymer electrolyte membrane fuel cells (PEMFCs), ALD has revolutionized catalyst layer design by precisely tuning Pt-based nanoparticles, achieving a 2.5-fold increase in mass activity while significantly reducing platinum loading and improving carbon support corrosion resistance. Furthermore, ALD coatings on direct methanol fuel cell (DMFC) electrodes have effectively decreased methanol crossover and nickel solubility, mitigating long-term degradation. Despite its transformative potential, ALD expression challenges related to high processing costs, slow deposition rates, and precursor limitations, which hinder large-scale industrial adoption. Future research should focus on scalable ALD processes, hybrid deposition techniques, and advanced precursor development to enhance throughput, cost-effectiveness, and material compatibility. By associating the gap between atomic scale precision and large-scale manufacturing, ALD holds immense promise for next-generation fuel cells with higher efficiency, longer lifespan, and greater commercial viability.