Carbon nanotube–titanium dioxide nanocomposite support for improved activity and stability of an iridium catalyst toward the oxygen evolution reaction

Abstract

In order to improve the electrocatalytic activity and stability of an iridium (Ir) nanoparticle catalyst toward the oxygen evolution reaction (OER) in acidic electrolyte, carbon nanotube and titanium dioxide nanocomposites (CNT@TiO₂) are presented as a high-performance support. TiO₂ was synthesized on CNTs by using a novel layer-by-layer solution coating method that mimics atomic layer deposition (ALD) but is cost-effective and scalable. In the nanocomposites, CNTs serve as the electron pathways and the surface TiO₂ layers protect CNTs from corrosion under the harsh OER conditions. Thus, CNT@TiO₂ demonstrates excellent corrosion resistance as well as a high electrical conductivity (1.6 ± 0.2 S cm⁻¹) comparable to that of Vulcan carbon (1.4 S cm⁻¹). The interaction between Ir and TiO₂ promotes the formation of Ir(III) species, thereby enhancing the OER activity and stability of the Ir nanoparticle catalyst. Compared to commercial carbon-supported Ir (Ir/C) and Ir black catalysts, CNT@TiO₂-supported Ir exhibits superior OER activity and stability.