Water electrolysis is the key to a decarbonized energy system, as it enables the conversion and storage of renewably generated intermittent electricity in the form of hydrogen. However, reliability challenges arising from titanium‐based porous transport layers (PTLs) have hitherto restricted the deployment of next‐generation water‐splitting devices. Here, it is shown for the first time how PTLs can be adapted so that their interface remains well protected and resistant to corrosion across ≈4000 h under real electrolysis conditions. It is also demonstrated that the malfunctioning of unprotected PTLs is a result triggered by additional fatal degradation mechanisms over the anodic catalyst layer beyond the impacts expected from iridium oxide stability. Now, superior durability and efficiency in water electrolyzers can be achieved over extended periods of operation with less‐expensive PTLs with proper protection, which can be explained by the detailed reconstruction of the interface between the different elements, materials, layers, and components presented in this work.

Copper(II) formate is efficiently incorporated into the pores of a 2D imine-based covalent organic framework (COF) via coordination with the phenol and imine groups. The coordinated metal ion is then reduced to Cu(I) with a thermal treatment that evolves CO 2 . After loading with hydrogen gas, the majority of H 2 desorbs from the coordinatively saturated Cu(II) COF at temperatures < −100 °C. However, the activated Cu(I) COF retains adsorbed H 2 above room temperature. Adsorption/ desorption of H 2 was highly reversible. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) strongly supports a molecular hydrogen interaction with Cu(I). A Kissinger analysis of variable ramp rate desorption experiments estimates the enthalpy of H 2 desorption from Cu(I) at 15 kJ mol −1 . The results represent an advance toward practical H 2 storage and delivery in a lightweight, stable, and highly versatile material.

We present an investigation of the structure and rheological behavior of catalyst inks for low-temperature polymer electrolyte membrane water electrolyzers. The ink consists of iridium oxide (IrO 2 ) catalyst particles and a Nafion ionomer dispersed in a mixture of 1-propanol and water. The effects of ionomer concentration and catalyst concentration on the microstructure of the catalyst ink were studied. Studies on dilute inks (0.1 wt % IrO 2 ) using zeta potential and dynamic light scattering measurements indicated a strong adsorption of the ionomer onto the catalyst particles which resulted in an increase in the ζ-potential and the z-average diameter. Steady-shear and dynamic-oscillatory-shear rheological measurements of concentrated IrO 2 dispersions (35 wt % IrO 2 ) indicated that the particles are strongly agglomerated in the absence of the ionomer. The addition of even a small amount of the ionomer (2.4 wt % with respect to total solids) caused the rheology to transition from shear thinning to Newtonian because of the reduction in agglomerated structure due to stabilization of the aggregates by the ionomer, consistent with the behavior of dilute inks. At intermediate ionomer loadings, between 2.4 and 9 wt %, the viscosity increased with increasing ionomer wt %, though remained Newtonian, predominantly due to the increasing ionomer volume fraction in the ink. For ionomer loadings greater than 9 wt %, the particles were found to be flocculated, likely induced by a dispersed ionomer. The flocculated inks exhibited strong shear-thinning and gel-like behaviors in steady-shear and oscillatoryshear rheology. The onset of flocculation was found to be sensitive to the catalyst concentration, where below 35 wt % of IrO 2 , flocculation was not observed. The rheological observations were further verified by ultra-small-angle X-ray scattering.

Mitigating high overpotential losses originating from the sluggish oxygen evolution reaction (OER) during water electrolysis is key to establishing a sustainable hydrogen generation technique. Herein we report a Co-imidazolate framework (ZIF 67) as an OER catalyst that exhibits high activity in both a three electrode cell and an electrolyzer. Additionally, Fe, Ni, and Zn have been incorporated into ZIF 67 to evaluate their effects on the OER activity of ZIF 67. Due to the high charge conductivity of ZIF 67, none of the reported catalyst was carbonized at high temperature, a process that is generally accompanied by significant mass loss. Hence, in addition to being highly active, these catalysts are scalable which makes them promising candidates for application in commercial power markets.

Polymer electrolyte membrane water electrolyzers (PEMWEs) are devices of paramount importance, enabling the large-scale storage of hydrogen. A transition towards lower catalyst loadings and intermittent operation is needed for widespread utilization, but the extent of degradation of catalyst layer constituents and further structural changes have not been widely explored. The multitude and complexity of degradation mechanisms requires characterization that can explore surfaces and interfaces at a range of length-scales to probe all changes of constituents within the catalyst later. This paper presents such an approach, featuring scanning electron microscopy, scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy, X-ray photoelectron and absorption spectroscopies, and transmission X-ray microscopy with X-ray absorption near-edge structure chemical mapping, to study degradation of the catalyst layer with a focus on comparing intermittent and steady-state operation. Catalyst changes including dissolution, oxidation, and agglomeration were observed, as well as redistribution and dissociation of the ionomer, and the smaller scale changes were found to cause the formation of voids and segregation of constituents at the larger scale. These findings highlight the importance of detailed analysis of catalyst layer degradation to propose mitigation strategies and improve long-term performance at various operating conditions.