The rational design of electrochemical oxygen evolution reaction (OER) electrocatalyst is essential for the development of efficient and sustainable electrochemical energy conversion, storage and electrolysis applications. One of the remaining limitations of the low‐temperature electrolyzers is the large amounts of highly scarce and expensive iridium used as the OER electrocatalysts. This could be solved by applying much smaller amounts of iridium on efficient and stable support. Here we present a very promising functionality of titanium oxynitride (TiONx) high‐surface‐area support that effectively disperses the iridium nanoparticles, exhibits good intrinsic electrical conductivity and stability and thus promises efficient reduction of the noble‐metal loading in electrolyzers gas diffusion electrodes. The new nanocomposite made of approximately 3 nm‐sized iridium nanoparticles finely dispersed on TiONx support is produced using a novel synthetic route. Extensive characterization shows that the new composites exhibit an electronic interaction with the support and, ultimately, a high OER performance in acidic media.

In recent years, conversion chemical reactions, which are driven by ion diffusion, emerged as an important concept for formation of nanoparticles. Here we demonstrate that the slow anion diffusion in anion exchange reactions can be efficiently used to tune the disorder strength and the related electronic properties of nanoparticles. This paradigm is applied to high-temperature formation of titanium oxynitride nanoribbons, Ti(O,N), transformed from hydrogen titanate nanoribbons in an ammonia atmosphere. The nitrogen content, which determines the chemical disorder through random O/N occupancy and ion vacancies in the Ti(O,N) composition, increases with the reaction time. The presence of disorder has paramount effects on resistivity of Ti(O,N) nanoribbons. Atypically for metals, the resistivity increases with decreasing temperature due to the weak localization effects. From this state, superconductivity develops below considerably or completely suppressed critical temperatures, depending on the disorder strength. Our results thus establish the remarkable versatility of anion exchange for tuning of the electronic properties of Ti(O,N) nanoribbons and suggest that similar strategies may be applied to a vast number of nanostructures.

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