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Water electrolysis will be an essential element of the future energy system, with hydrogen serving as a climate-friendly energy storage medium. To make electrolyzers suitable for market penetration at scale, the cost of manufacturing megawatt electrolyzers must be minimized, with no detrimental effects to their performance and lifetime. Here we show a facile and cost-effective manufacturing method to produce one-piece Ti-based bipolar plates. Low-cost and commercially and readily available feedstock materials (blank sheets, expanded metals and nonwovens) are positively joined using an innovative welding process, diffusion bonding. This approach reduces the contact resistances that can occur with multi-part bipolar plates by around 75%, reducing the number of components and therefore significantly simplifying stack assembly. Ex-situ tests on the contact pressure distribution on the active cell surface reveal a homogeneous pattern with values of about 3.75 MPa (± 1.25 MPa). In a first proof-of-concept, a five-cell short stack with a 100 cm2 active cell area, average cell voltages of 1.71 V at 2 A cm−2 could be achieved using our new stack concept. • Detailed insight into the plate design, construction, production and verification. • Main feature of the novel bipolar plate is the one-piece-approach. • Development of a welding-based production process; elimination of contact resistances. • Approach increases the reliability and decreases the duration of the stack assembly. [ABSTRACT FROM AUTHOR]

Commercialized implementations of anion exchange membrane water electrolysis (AEMWE) require stable operation at high current density. To achieve this, ohmic, electrochemical and concentration polarizations are supposed to be exceedingly suppressed. Among all crucial materials, porous electrodes with catalyst coatings extensively affect the above polarizations, which are highly sensitive to specific mechanical pressure for cell assembly. However, the imposed mechanical pressure and its effects on cell performance are rarely reported in AEMWE cells. Here, quantitative characterizations of mechanical pressure and its effects on i) physical properties of catalyst coated electrodes and ii) corresponding single-cell performance are comprehensively investigated. First, the imposed mechanical pressure on membrane electrode assembly (MEA) is controlled by different total thickness gaps between anode/cathode and poly-tetra-fluoroethylene (PTFE) gaskets (Δd = 0, 100, 200, 300 μm). Second, the above resulted distributions of mechanical pressure are quantitatively studied by a mechanical pressure tracking method. Third, the influence of the mechanical pressure on the physical properties of the electrodes and cell performance are demonstrated. It is proved that the mechanical pressure of ca. 0.5 MPa is comprehensively beneficial for suppressing internal resistance (R Ω) and charge transfer resistance (R ct), with slightly increased mass diffusion resistance (R md) and hydrogen crossover. This study unveils the intrinsic effects of mechanical pressure on cell performance and provides critical insights into baseline benchmarking and single-cell even stack optimization. [Display omitted] • Dependence of cell mechanics, mass transport, wettability over contact pressure. • Electrochemical performance and internal resistance in the pressure range 0–6 MPa. • 0.5 MPa is optimal contact pressure to suppress R Ω /R ct and relieve R md. • Membrane thickness (≥50 μm) favorable to prevent membrane damage. • Pre-assembly and gradually increased mechanical pressure are esential for mounting. [ABSTRACT FROM AUTHOR]

Due to water uptake, the polymer membrane of polymer electrolyte membrane water electrolyzers (PEMWE) swells, increases in thickness and so induces swelling pressure. The water content in the membrane and catalyst coated membrane (CCM), respectively, defines the protonic conductivity, which has a significant impact on the performance of a PEMWE. In order to ensure the gas tightness of the PEMWE and increase the thermal and electrical connectivity between the different layers, the entire electrolyzer is compressed. Whether and in which way the swelling of the CCM is influenced by applying pressure or influences the surrounding layers is investigated in this study using a special compression device and X-ray computer tomography (CT). CT scans were carried out and the resulting cross-sectional images analyzed. Five different compression pressures between 0.36 and 1.63 MPa were applied for the dry (28 °C, atmospheric humidity) and wet (28 °C, surrounded by liquid water) states. The thickness change of the CCM and adjacent porous transport layers (PTL) was then measured. Due to the compression pressure, the thickness of the CCM decreased by 5%. For lower pressures, the carbon paper PTL compensates more of the swelling than the titanium felt PTL. For higher pressures, the ratio is inverse. [Display omitted] • Visualization of membrane-swelling • Increasing the clamping pressure locally reduces the water uptake of a Nafion® 212 membrane • Membrane swelling reduces the porosity of the PTL by one percentage-point. [ABSTRACT FROM AUTHOR]