Hydrogen produced by water electrolysis is a promising storage medium for renewable energy. Reducing the capital cost of proton exchange membrane (PEM) electrolyzers without losing efficiency is one of its most pressing challenges. Gas diffusion layers (GDL), such as felts, foams, meshes and sintered plates, are key stack components, but these are either inefficient or expensive. This study presents a new type of GDL produced via vacuum plasma spraying (VPS), which offers a large potential for cost reduction. With this technology, it is possible to introduce a gradient in the pore-size distribution along the thickness of the GDL by varying the plasma parameters and titanium powder particle sizes. This feature was confirmed by cross-section scanning electron microscopy (SEM). X-ray computed tomography (CT) and mercury intrusion porosimetry allowed determining the porosity, pore radii distribution, and pore entry distribution. Pore radii of ca. 10 μm could be achieved in the layers of the GDL close to the bipolar plate, while those in contact with the electrodes were in the range of 5 μm. The thermally sprayed Ti-GDLs allowed achieving PEM electrolyzer performances comparable to those of the state-of-the-art sintered plates and far superior than those of meshes. Moreover, a numerical model showed that the reduced capillary pressure and tortuosity eliminates mass transport limitations at 2 A cm⁻². The results presented herein demonstrate a promising solution to reduce the cost of one of the most expensive components of the stack.

Proton exchange membrane water electrolysis (PEMWE) is the most promising technology for sustainable hydrogen production. However, it has been too expensive to compete with current state-of-the-art technologies due to the high cost of titanium bipolar plates (BPPs) and porous transport layers (PTLs). Here, we report a high-performance, durable and low-cost PEMWE cell with coated stainless steel (ss) BPPs and PTLs. When using uncoated ss components in the PEMWE cell, the cell depolarizes rapidly, reaching 2 V at only 0.15 A cm⁻². After the application of non-precious metal coatings of Ti and Nb/Ti on the ss-BPP and ss-PTL, respectively, the current density can be increased by a factor of 13 while maintaining the same performance. Extensive physical and electrochemical characterization supported by pore network modelling shows that the Nb/Ti coating on the ss-PTL leads to efficient water and gas transport at the interface with the anode. The PEMWE cell with coated ss components was evaluated in an accelerated stress test (AST) for more than 1000 h. No sign of Fe contamination in either the membrane or the electrodes is observed at the end of the test. With our results, we demonstrate that PEMWE cells can be manufactured almost entirely in ss, facilitating an unprecedented cost reduction in this technology and advancing the widespread use of green H₂.

We have developed a highly active nanostructured iridium catalyst for anodes of proton exchange membrane (PEM) electrolysis. Clusters of nanosized crystallites are obtained by reducing surfactant‐stabilized IrCl₃ in water‐free conditions. The catalyst shows a five‐fold higher activity towards oxygen evolution reaction (OER) than commercial Ir‐black. The improved kinetics of the catalyst are reflected in the high performance of the PEM electrolyzer (1 mg_Ir cm⁻²), showing an unparalleled low overpotential and negligible degradation. Our results demonstrate that this enhancement cannot be only attributed to increased surface area, but rather to the ligand effect and low coordinate sites resulting in a high turnover frequency (TOF). The catalyst developed herein sets a benchmark and a strategy for the development of ultra‐low loading catalyst layers for PEM electrolysis.

Proton exchange membrane water electrolysis is a promising technology to produce green hydrogen from renewables, as it can efficiently achieve high current densities. Lowering iridium amount in oxygen evolution reaction electrocatalysts is critical for achieving cost-effective production of green hydrogen. In this work, we develop catalysts from Ir double perovskites. Sr₂CaIrO₆ achieves 10 mA cm⁻² at only 1.48 V. The surface of the perovskite reconstructs when immersed in an acidic electrolyte and during the first catalytic cycles, resulting in a stable surface conformed by short-range order edge-sharing IrO₆ octahedra arranged in an open structure responsible for the high performance. A proton exchange membrane water electrolysis cell is developed with Sr₂CaIrO₆ as anode and low Ir loading (0.4 mg_Ir cm⁻²). The cell achieves 2.40 V at 6 A cm⁻² (overload) and no loss in performance at a constant 2 A cm⁻² (nominal load). Thus, reducing Ir use without compromising efficiency and lifetime.