Intrinsic oxygen evolution reaction activity and stability enhancement of IrOx electrocatalysts by microwave irradiation

Microwave induced surface and bulk structural alterations enhance the OER activity and durability of the carbon supported Ir-Oxide (IrO x /C) electrocatalyst. • A surfactant free hydrolysis approach was successfully implemented to synthesize colloidal IrO x nanoparticles supported on high surface area C (IrO x /C) • OER activity shows ∼ 5 times higher than unsupported IrO 2. • Post microwave irradiation further improved OER activity and durability to 84% retention without compromising particle size. • PDF suggests a transition from a rutile-like structure to hollandite-like structure. A surfactant free hydrolysis approach was used to synthesize colloidal IrO x nanoparticles, which were loaded on a high surface area carbon support to obtain IrO x (IrO x /C), having a mass specific oxygen evolution reaction (OER) activity ∼ 5 times higher than that of unsupported IrO 2 , a benchmark commercial OER electrocatalyst. The synthesized IrO x /C and the unsupported IrO 2 were then treated under microwave (MW) irradiation and their electrocatalytic activity and stability towards OER in acidic media was investigated. For both electrocatalysts, the microwave treatment improved the mass specific OER activity and enhanced the durability, with no apparent increase in the IrO x nanoparticle size, demonstrated in a potentiodynamic accelerated stress test (AST). Surface chemical state studies of the as-synthesized and MW-treated IrO x /C samples suggest increased Ir-O-Ir bonding on expense of the Ir-OH bonding through MWI. Further, using X-ray pair distribution function (PDF) analysis it was suggested that the MW treated IrO x /C leads to a gradual change in the local coordination from a rutile-like structure to a highly OER active hollandite-like structure. The presented OER catalyst synthesis route and microwave irradiation approach may be put to use as a scalable method for the stability enhancement of the IrO x electrocatalysts for acidic water electrolysis.