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• Ni(OOH) catalysts decorated by iron oxide atomic layer deposition are demonstrated. • Surface iron on pm on Ni(OOH) catalystsis responsible for high OER OER activity. • Thick, high surface area Ni-Fe(OOH) catalysts require bulk iron for highest activity. • Ni-FeO x films deposited by ALD exhibit high OER activity and good corrosion resistance. Atomic layer deposition (ALD) has become a versatile tool in catalysis, allowing for precise synthesis of catalysts useful for gaining fundamental understanding of complex systems. In this work, ALD was used to perform surface-directed modification of Ni(OH) 2 /Ni(OOH) electrocatalysts for the oxygen evolution reaction (OER) to elucidate the different roles of iron as a surface dopant and of iron distributed throughout the NiOOH structure. Electrochemical and material characterization of FeO x ALD-modified Ni(OH) 2 indicates that iron is deposited on the surface of Ni(OH) 2 sheets without modifying its bulk properties. Sub-monolayer amounts of iron were deposited on the surface of Ni(OH) 2 using low cycle numbers of ALD. This surface iron results in high OER activity, characteristic of Ni-Fe(OOH) catalysts. Ni(OH) 2 /Ni(OOH) catalysts modified to incorporate iron throughout the structure were prepared by depositing large cycle numbers of FeO x ALD, which results in the deposition of a Fe 2 O 3 overlayer. Corrosion of this Fe 2 O 3 overlayer during electrochemical cycling in alkaline electrolyte leads to the incorporation of iron throughout the structure of Ni(OH) 2 /Ni(OOH) while leaving some iron at the surface. Incorporation of iron throughout the Ni(OH) 2 /Ni(OOH) structure was found to increase OER geometric activity for thick, high surface area Ni(OH) 2 /Ni(OOH) catalysts. Lastly, Ni-FeO x electrocatalysts synthesized fully by ALD were investigated for the OER; these catalysts demonstrated high OER activity and potential for photocatalysis applications. [ABSTRACT FROM AUTHOR]

Hybrid molecular layer deposition (MLD) has significant potential for the creation of ultrathin electrochemically active materials, due to its ability to combine organic and inorganic species to modulate film properties. However, only a limited number of hybrid MLD processes are demonstrated with electrochemically relevant elements, such as manganese. Here, a "manganicone" manganese hybrid MLD chemistry is developed using the precursors bis(ethylcyclopentadienyl)manganese and ethylene glycol. The resulting manganese alkoxide coordination networks are shown to have many interesting properties, including the ability to seamlessly fill high aspect ratio vias and the chemical conversion into manganese carboxylate in air over several hours at room temperature. Linear, self‐saturating growth is reported. Importantly, hybrid manganicone films annealed to 480 °C in air demonstrate a greater stability to restructuring during electrochemical testing than their inorganic counterparts grown by atomic layer deposition, without reducing the activity of the reactive sites on the manganese surface. Thus, hybrid manganese films grown by MLD have significant promise for use as catalysts for the oxygen evolution reaction and as electrodes in thin film batteries. [ABSTRACT FROM AUTHOR]