Iridium oxide is the state‐of‐the‐art catalyst for electrochemical water oxidation in an acidic medium. Despite being one of the rarest elements in the Earth's crust, there is a pressing need to maximize the utilization and longevity of active iridium centers. While conventional low‐temperature synthesis can yield nanostructures with high mass‐specific activity, they are often insufficiently stable during water oxidation. Structurally ordered iridium oxide is one of the most stable electrocatalysts utilized in polymer electrolyte membrane water electrolysis that benefits from the chemically ordered structure. However, its preparation requires thermal treatment at high temperatures, which improves its durability but can also result in reduced surface area and altered particle morphology. In this study, the challenge of controlling nanoparticle size during the preparation of structurally ordered iridium oxide is successfully addressed, which typically requires high‐temperature thermal treatment. By utilizing a silica nanoreactor as a hard template, a precise control is achieved over the nanoparticle size during high‐temperature thermal treatment. This approach maintains high durability while avoiding the common problem of reduced surface area and altered particle morphology. Specifically, this study is able to synthesize iridium oxide nanoparticles at temperatures up to 800 °C, while keeping their dimensions below 10 nm.

The utilization of biomass is one of the major challenges for the transition from fossil to renewable resources. Often, the separation of the desired product from the reaction mixture is the most energy‐intensive step. Liquid‐phase adsorption is a promising separation technology that could significantly improve downstream processing in biorefineries. Highly hydrophobic adsorbents were applied for the separation of lactic acid (LA) from aqueous solutions and to avoid the formation of gypsum as a byproduct. High uptakes and selectivity were obtained in single‐solute and co‐adsorption experiments. Porous hyper‐crosslinked polymers (HCP) and polymer‐based spherical activated carbon performed best and showed excellent selectivity for the selective removal of LA. Desorption experiments revealed that HCP was the ideal adsorbent for the separation of LA from aqueous solution and enabled the production of gypsum‐free LA.

The copper-catalyzed electrochemical CO 2 reduction reaction represents an elegant pathway to reduce CO 2 emissions while producing a wide range of valuable hydrocarbons. The selectivity for these products depends strongly on the structure and morphology of the copper catalyst. However, continued deactivation during catalysis alters the obtained product spectrum. In this work, we report on the stabilizing effect of three different carbon supports with unique pore structures. The influence of pore structure on stability and selectivity was examined by high-angle annular dark field scanning transmission electron microscopy and gas chromatography measure-ments in a micro-flow cell. Supporting particles into confined space was found to increase the barrier for particle agglomeration during 20 h of chronopotentiometry measurements at 100 mA cm À 2 resembling long-term CO 2 reduction conditions. We propose a catalyst design preventing coalescence and agglomeration in harsh electrochemical reaction conditions, exemplarily demonstrated for the electrocatalytic CO 2 reduction. With this work, we provide important insights into the design of stable CO 2 electrocatalysts that can potentially be applied to a wide range of applications.[a] E.

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