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Nano-electrochemical tools to assess individual catalyst entities are critical to comprehend single-entity measurements. The intrinsic electrocatalytic activity of an individual well-defined Co3 O4 nanoparticle supported on a carbon-based nanoelectrode is determined by employing an efficient SEM-controlled robotic technique for picking and placing a single catalyst particle onto a modified carbon nanoelectrode surface. The stable nanoassembly is microscopically investigated and subsequently electrochemically characterized. The hexagonal-shaped Co3 O4 nanoparticles demonstrate size-dependent electrochemical activity and exhibit very high catalytic activity with a current density of up to 11.5 A cm-2 at 1.92 V (vs. RHE), and a turnover frequency of 532±100 s-1 at 1.92 V (vs. RHE) towards catalyzing the oxygen evolution reaction.

Mo-doped BiVO4 has emerged as a promising material for photoelectrodes for photoelectrochemical water splitting, however, still shows a limited efficiency for light-driven water oxidation. We present the influence of an oxygen-evolution catalyst composed of Ni, Fe, and Cr oxides on the activity of Mo:BiVO4 photoanodes. The photoanodes are prepared by spray-coating, enabling compositional and thickness gradients of the incorporated catalyst. Two different configurations are evaluated, namely with the catalyst embedded into the Mo:BiVO4 film or deposited on top of it. Both configurations provide a significantly different impact on the photoelectrocatalytic efficiency. Structural characterisation of the materials by means of SEM, TEM and XRD as well as the photoelectrocatalytic activity investigated by means of an optical scanning droplet cell and in situ detection of oxygen using scanning photoelectrochemical microscopy are presented.

In article number https://doi.org/10.1002/advs.201801029, Kolleboyina Jayaramulu, Justus Masa, Wolfgang Schuhmann, Roland A. Fischer, and co‐workers report simple and facile synthesis of cobalt‐based 2D zeolite imidazole framework nanosheets [Co‐ZIF‐9(III)] by mechano‐chemical grinding with subsequent liquid‐phase exfoliation. The resultant 2D material exhibits highly efficient oxygen evolution reaction (OER) activity under alkaline conditions, attributed to increased accessibility of redox‐active cobalt oxyhydroxide active sites with a nitrogen coordination environment N4CoOOH, and efficiently mimics Co‐Porphyrin electrocatalysts.

2D layered materials, including metal‐di‐chalcogenides and transition metal layered double hydroxides, among others, are intensively studied because of new properties that emerge from their 2D confinement, which are attractive for advanced applications. Herein, 2D cobalt ion (Co2+) and benzimidazole (bIm) based zeolite‐imidazole framework nanosheets, ZIF‐9(III), are reported as exceptionally efficient electrocatalysts for the oxygen evolution reaction (OER). Specifically, liquid‐phase ultrasonication is applied to exfoliate a [Co4(bIm)16] zeolite‐imidazole framework (ZIF), named as ZIF‐9(III) phase, into nanoscale sheets. ZIF‐9(III) is selectively prepared through simple mechanical grinding of cobalt nitrate and benzimidazole in the presence of a small amount of ethanol. The resultant exfoliated nanosheets exhibit significantly higher OER activity in alkaline conditions than the corresponding bulk phases ZIF‐9 and ZIF‐9(III). The electrochemical and physicochemical characterization data support the assignment of the OER activity of the exfoliated nanosheet derived material to nitrogen coordinated cobalt oxyhydroxide N4CoOOH sites, following a mechanism known for Co‐porphyrin and related systems. Thus, exfoliated 2D nanosheets hold promise as potential alternatives to commercial noble metal electrocatalysts for the OER.