Enhancing Iridium Nanoparticles' Oxygen Evolution Reaction Activity and Stability by Adjusting the Coverage of Titanium Oxynitride Flakes on Reduced Graphene Oxide Nanoribbons' Support

Hydrogen production from solar energy is currently considered the best alternative to fossil fuels. Thus, materials enabling efficient and sustainable energy conversion and storage need to be developed. Iridium is still the only material used in proton exchange membrane electrolyzers that efficiently catalyze hydrogen evolution counter-reaction, namely, the oxygen evolution reaction (OER) for electrochemical water splitting in acidic media. With no practical alternatives that can sustain the harsh reaction conditions, new approaches need to be developed to increase the utilization of this scarce metal. Hereby, a carbon-ceramic nanocomposite material is investigated, where Ir nanoparticles and nanoflakes of titanium oxynitride (TiONx) are deposited on the surface of reduced graphene oxide nanoribbons (rGONRs). OER performance is shown to be dependent on the mutual distribution of the Ir-TiONx-rGONR phases and in the best case leads up to 30 times higher activity relative to the commercial IrO2 benchmark. Adjusting the domains of different chemical nature within the same hybrid nanocomposite material through the formation of heterojunctions is shown to boost OER performance. This work demonstrates how fine-tuning of morphology, composition, and particle distribution of the carbon-ceramic catalytic material can introduce a strong synergistic effect on OER activity and stability of iridium.