Ultrasonic Spraying for Iridium Layer on Ti-Based PTL

Ultrasonic Spraying of Ultra-Low-Load Iridium Layers on Titanium-Based PTL to Construct Multifunctional Interfaces for Enhanced PEMWE Performance

Proton Exchange Membrane Water Electrolysis (PEMWE) has emerged as the core technology for large-scale green hydrogen production, benefiting from high hydrogen purity, fast response speed, and adaptability to fluctuations in renewable energy power generation. However, its anodic Oxygen Evolution Reaction (OER) suffers from sluggish reaction kinetics, necessitating the use of precious iridium (Ir)-based catalysts. Meanwhile, titanium-based Porous Transport Layers (PTL) are prone to forming passivation layers under strong oxidation and high-potential operating conditions, leading to rising interfacial impedance and performance degradation. In addition, the excessive consumption of iridium severely restricts cost reduction and efficiency improvement in industrialization. Adopting ultrasonic spraying technology to deposit ultra-low-load iridium layers on the surface of titanium-based PTL and precisely construct multifunctional interfaces integrating catalysis, electrical conduction and corrosion resistance has become a critical approach to break through the performance and cost bottlenecks of PEMWE.

Titanium-based PTL is the mainstream mass transfer carrier for PEMWE anodes due to its excellent electrical conductivity, high mechanical strength and acid corrosion resistance. Nevertheless, under the anodic high potential (>1.6 V vs RHE) and strong oxidizing environment, a non-conductive TiOₓ passivation film spontaneously forms on the titanium surface, which drastically increases the contact resistance between the electrode and the catalytic layer, aggravates the ohmic loss of the cell, and reduces the energy conversion efficiency. Traditional solutions rely on high-load precious metal (Ir, Pt, etc.) coatings to protect PTL, with the iridium loading of commercial devices often exceeding 1 mg·cm⁻². Although passivation can be suppressed, the scarcity of resources and high costs hinder the industrialization progress of PEMWE. Achieving reduced interfacial impedance, improved catalytic activity and enhanced structural stability simultaneously under ultra-low iridium loading has become a core challenge urgently to be solved by the industry.

With the advantages of precise atomization and controllable deposition, ultrasonic spraying technology provides an ideal solution for the efficient preparation of ultra-low-load iridium layers. Through high-frequency ultrasonic vibration, the iridium-based catalyst slurry is atomized into micron-scale uniform droplets and deposited on the surface of titanium-based PTL in a non-contact spraying manner, enabling precise regulation of coating thickness, microstructure and iridium loading. Compared with traditional processes such as conventional spraying and sputtering, ultrasonic spraying effectively avoids catalyst agglomeration, uneven coating thickness and substrate pore blockage. Even at an ultra-low iridium loading range of 0.025–0.1 mg·cm⁻², a continuous, dense and uniform ultra-thin iridium layer can be formed. This precision coating method fully exposes the active sites of iridium atoms, raising the catalyst utilization rate to over 90% — far higher than the 30%–50% of traditional processes — and providing process support for the goal of “low loading and high performance”.

Modifying titanium-based PTL with an ultra-low-load iridium layer enables the construction of optimized interfaces with multiple functions, improving the comprehensive performance of PEMWE from multiple dimensions.First, passivation resistance and electrical conduction: The continuous ultra-thin iridium layer isolates the titanium substrate from the strong oxidizing electrolyte, inhibiting the generation of TiOₓ passivation layers at the source, reducing the interfacial contact resistance by more than 60% and significantly lowering the ohmic overpotential.Second, auxiliary catalytic performance: The iridium layer itself exhibits excellent OER catalytic activity, acting as an “ultra-thin active layer” to work synergistically with the traditional anode catalytic layer, expanding the three-phase reaction interface, accelerating water decomposition and oxygen evolution, and reducing the kinetic overpotential of the reaction.Third, mass transfer optimization: The iridium layer prepared by ultrasonic spraying features a uniform pore structure and moderate surface roughness, which ensures efficient water transport and rapid oxygen desorption, avoids increased mass transfer resistance caused by traditional thick coatings, and enhances stability under high current density.

Experimental data verify that when the iridium loading on the titanium-based PTL surface is only 0.025 mg·cm⁻², the electrode modified by ultrasonic spraying achieves the same level of interfacial impedance and cell performance as traditional high-load (1 mg·cm⁻²) electrodes. At an operating voltage of 1.9 V, the current density of the electrolyzer exceeds 3 A·cm⁻². In the galvanostatic stability test at 1 A·cm⁻², stable operation lasts more than 300 hours without obvious performance attenuation. Compared with unmodified titanium-based PTL, the multifunctional interface reduces the PEMWE cell voltage by 30–50 mV, increases the energy conversion efficiency by 5%–8%, and cuts iridium consumption by over 40 times. This directly lowers the catalyst cost by more than 70%, realizing dual breakthroughs in performance and economic efficiency.

From the perspective of industrialization, ultrasonic spraying technology boasts good scalability and can be integrated into roll-to-roll continuous production systems to meet the demand for high-speed and stable coating of wide-width titanium-based PTL. The process features high slurry compatibility and adapts to various solvent systems including water-based and alcohol-based slurries. Without high-pressure airflow impact, it avoids titanium substrate deformation and membrane damage, ensuring the consistency of batch products. With the in-depth integration of low-iridium catalyst systems and interface engineering technology, the technical scheme of modifying titanium-based PTL via ultrasonic spraying of ultra-low-load iridium layers will further promote the commercial application of PEMWE in green hydrogen production, large-scale energy storage and other fields, providing crucial technical support for global energy transition and the achievement of the “dual carbon” goals.

In the future, the research directions of this technology will focus on three aspects: first, developing iridium-based single-atom and alloyed catalysts to further reduce iridium loading and enhance intrinsic activity; second, optimizing ultrasonic spraying process parameters to precisely regulate the microscopic morphology and interfacial adhesion of iridium layers; third, exploring the attenuation mechanism of multifunctional interfaces under long-term operating conditions and extending the service life of electrodes through interface structure design. Through technological iteration and innovation, the performance and cost bottlenecks of PEMWE will be continuously broken through, helping the green hydrogen industry march into a new stage of high-efficiency, low-cost and large-scale development.

About Cheersonic

Cheersonic is the leading developer and manufacturer of ultrasonic coating systems for applying precise, thin film coatings to protect, strengthen or smooth surfaces on parts and components for the microelectronics/electronics, alternative energy, medical and industrial markets, including specialized glass applications in construction and automotive.

Our coating solutions are environmentally-friendly, efficient and highly reliable, and enable dramatic reductions in overspray, savings in raw material, water and energy usage and provide improved process repeatability, transfer efficiency, high uniformity and reduced emissions.