Identifying the intrinsic electrocatalytic activity of nanomaterials is challenging, as their characterization usually requires additives and binders whose contributions are difficult to dissect. Herein, we use nano impact electrochemistry as an additive-free method to overcome this problem. Due to the efficient mass transport at individual catalyst nanoparticles, high current densities can be realized. High-resolution bright-field transmission electron microscopy and selected area diffraction studies of the catalyst particles before and after the experiments provide valuable insights in the transformation of the nanomaterials during harsh oxygen evolution reaction (OER) conditions. We demonstrate this for 4 nm sized CoFe 2 O 4 spinel nanoparticles. It is revealed that these particles retain their size and crystal structure even after OER at current densities as high as several kA•m −2 . The steady-state current scales with the particle size distribution and is limited by the diffusion of produced oxygen away from the particle. This versatilely applicable method provides new insights into intrinsic nanocatalyst activities, which is key to the efficient development of improved and precious metal-free catalysts for renewable energy technologies.

The increasing number of surgical treatments performed per year requires novel approaches to inhibit implant‐associated infections, caused by multi‐antibiotic resistant bacteria. Silver ions (Ag+) are known for their effective antimicrobial activity. Therefore, a system that efficiently and locally releases the minimum required amount of Ag+ directly after the surgical treatment is in high demand. Herein we study electrochemically, microbiologically, microscopically and spectroscopically sacrificial Ag anode coatings for antibacterial implant applications. It is found that Ag dot arrays deposited on noble metals (Pd, Ir) release Ag+ much faster than continuous Ag thin films. The Ag+ release qualitatively scales with the difference of standard potentials between Ag and the noble metal. Furthermore, with higher numbers of Ag dots, the total amount of released Ag+ increases, while the release efficiency declines. Notably, an efficient killing of Staphylococcus aureus bacteria was seen for coatings containing as little as 23 ng of Ag per mm2. Thus, the use of sacrificial Ag anodes as highly efficient antibacterial coating materials is evaluated.

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