Polymer surfactant-assisted tunable nanostructures of amorphous IrOx thin films for efficient electrocatalytic water oxidation

Abstract

Transparent IrOx catalyst films for water oxidation were fabricated on fluorine-doped tin oxide electrodes from Ir precursor complex solutions containing Pluronic P123, Brij 58 or Pluronic F127 as surfactant structure directing agents (SDAs). The thin layers composed of highly dispersed and very small nanoparticles of ca. ≤2nm were formed for IrOx films derived by Pluronic P123 and Brij 58, both of which act as a ‘spacer’ between the Ir-building-blocks to inhibit further agglomeration of the nanoparticles. Pluronic F127 with relatively longer hydrophilic poly(ethylene oxide) blocks stabilizes Ir-complexes in the precursor solution due to stronger interaction between its longer EO-units and Ir-complexes, affording the organized mesoporous structures of ca. 8nm pores templated by micelles formed in the IrOx film derived by Pluronic F127. The cyclic voltammetry revealed the catalytic currents for water oxidation for the SDAs-derived IrOx films were 1.3–1.8 times higher than the IrOx film without SDA. The higher water oxidation activity observed is attributed to the higher intrinsic catalytic activity of Ir-sites on very small nanoparticles in the Pluronic P123 and Brij 58-derived IrOx films, whereas it is attributed to the increased number of active Ir-sites due to the organized mesoporous structures of the Pluronic F127-derived IrOx film.