Green hydrogen is a promising energy carrier to bridge the gap between supply and demand of renewable energies. Amongst the technologies to produce hydrogen by water splitting, proton exchange membrane water electrolysis (PEMWE) is one of the most promising approaches. The major advantages of this technology are a high power density resulting in a compact stack architecture, and its capability to follow fast load fluctuations. These two advantages are especially important considering a future scale-up of the technology to Gigawattscales and the connection to renewable, inherently intermittent energy sources. Due to their high activity and stability under the harsh PEMWE operation conditions (low pH and high potentials at elevated temperatures) of the acidic oxygen evolution reaction (OER), state-of-the-art electrocatalysts on the anode side of PEMWE cells are usually iridium-based. Although alternative materials such as ruthenium can show superior OER activity in acidic media compared to iridium, the higher dissolution rate of Ru under PEMWE conditions strongly constrains its long-term stability. However, the scarcity of iridium still limits the widespread and large-scale implementation of PEMWE. A scale-up of the annual implementation of PEMWE to 10 GW using state-of-the-art electrolyzers with loadings of 2 mgIr cm -2 , would require 7.5 t of iridium, whereas the global iridium supply in 2022 only amounted to 6.8 t per year. Calculations considering the scarcity of iridium and the projected scale-up to the GW-scale reveal that an iridium-specific power density of 50 -100 kW gIr -1 is required for a successful adoption of PEMWE. The iridium-specific power density in recent publications ranges between 9 -16 kW gIr -1 . Thus, the iridium utilization must be ultimately enhanced for a future scale-up of PEMWE. This is only achievable by designing electrodes with strongly reduced iridium loadings while simultaneously maintaining a high PEMWE performance. Decreasing the loading, however, usually involves a reduction of catalyst layer thickness. Importantly, it was shown that below a certain threshold of layer thickness or loading (e.g., for Umicore Elyst Ir75 0480: < 2 µm or < 0.5 mgIr cm -2 ), the structural integrity and, thus, the in-plane electrical connectivity within the layer is disrupted. Additionally, cracks can form during operation in these thin catalyst layers. In combination with the comparably large pore size of the porous transport layers (PTLs), these cracks result in disconnected and therefore inactive catalyst islands. This decreased catalyst utilization comes along with significant performance losses. To overcome the problems associated with too thin catalyst layers, the iridium content in the catalyst powder should be decreased to enable the fabrication of sufficiently thick catalyst layers with low iridium loadings. In other words, advanced electrode architectures require a high electrode thickness factor, which per definition is the electrode thickness as a function of catalyst loading. Common strategies to reduce the iridium content in the catalyst powder are either to alloy iridium with more abundant elements or to support the iridium. Alloying has been shown with many different elements, such as Fe , Cr , and Ni . However, the low dissolution stability of the alloying elements is a concern considering both catalyst durability and membrane poisoning. Using support materials for iridium catalysts instead can introduce a high dispersion of the iridium phase, thus increasing the amount of reaction sites. However, the electrical connection of the iridium sites must be ensured to render them active for the OER. To achieve this, several conductive supports have been tested, for example antimony-doped tin oxide (ATO) and tantalum-doped TiO2 showing high conductivity. But once more, the dissolution stability of these materials is questionable; illustratively, a high antimony dissolution from ATO has been shown in three-electrode electrochemical tests. To avoid support degradation, TiO2 is established as a stable support, both in academic research and industry. Nevertheless, the electrical conductivity of TiO2 is so low that it is regarded as insulator for the application in PEMWE. Therefore, the conductivity of TiO2supported iridium catalysts must be ensured solely by the iridium phase. To guarantee a percolating pathway from particle to particle, a core-shell structure is usually aimed for. Here, a delicate balance must be found between reducing the iridium content on the one hand and achieving sufficient conductivity on the other hand. Generally, to ultimately decrease the iridium content, an iridium shell as thin as possible is desirable, which, however, reduces the electric conductivity. Additionally, choosing support particles with a low specific surface area can decrease the required amount of iridium, because less surface needs to be covered for a closed shell, as pointed out by Bernt et al. In this regard, photodeposition is a suitable method to produce core-shell particles. During photodeposition synthesis, a mixture of semiconducting particles (e.g., TiO2) and metal ions (e.g., Ir X+ ) is exposed to electromagnetic radiation with an energy exceeding the band gap energy of the semiconductor (e.g., UV light). The irradiation generates electron-hole pairs inside the semiconductor. Usually, a sacrificial agent is introduced as a hole scavenger, enabling the electron in the conduction band to reduce metal ions on the semiconductor surface. During this process, metal ions are deposited as metal (oxide) seeds on top of the semiconducting particles. However, photodeposition processes are influenced by various parameters, such as the choice of precursor, hole scavenger, pH, and gas saturation as pointed out by Wenderich et al. Additionally, the role of the hole scavenger is still not well understood in various photodeposition studies. Nonetheless, the photodeposition process has found application in the synthesis of noble metal/semiconductor compounds in different research areas, such as photocatalytic water splitting, wastewater treatment, and air purification. While first successes about photodeposited iridium oxide on TiO2 are reported, they are still scarce in the context of PEMWE. Albeit this demonstrates the general applicability of photodeposition to this research field, neither a continuous shell was achieved so far, nor was the catalyst characterized on PEMWE single-cell level. In this work, we present TiO2@IrOx core-shell particles with a homogeneous, nanometer-thin iridium-shell as OER electrocatalyst, that are synthesized by a facile and scalable photodeposition process. Combining this novel synthesis method with low surface area TiO2 support particles enables the synthesis of catalysts with reduced iridium contents down to only 40 wt% iridium. Herein, we first extensively analyze the novel synthesis method using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and nuclear magnetic resonance (NMR) spectroscopy to shed light on the shell formation mechanism. Moreover, the final catalyst is compared to commercially available catalysts in both three-electrode setups and single-cell testing in a catalyst-coated membrane (CCM) configuration in terms of performance and stability. We demonstrate that our catalyst layer architecture outperforms state-of-the-art catalyst layers at low loadings approaching the power density target of the U.S. Department of Energy (DOE) for 2026 of 10 kW gPGM -1 . The stability of the catalyst was tested using a scanning flow cell setup coupled on-line to an inductively coupled plasma mass spectrometer (SFC-ICP-MS) as well as in singlecell measurements indicating a durability, which is on par with modern, iridium-based OER catalysts. In the end, we emphasize that the presented synthesis method is readily scalable, as large UV reactors for water purification with throughputs of > 1000 m 3 per day are already implemented.