Electrochemical fabrication of IrOx nanoarrays with tunable length and morphology for solid polymer electrolyte water electrolysis

For a typical Proton exchange membrane (PEM) water electrolysis system, reducing the amount of Ir loading at the anode in membrane electrode assembly (MEA), while maintaining the performance, is still a big challenge. Here, to improve the performance of catalyst layer for oxygen evolution reaction (OER) in an acidic medium, vertical aligned IrOx nanoarrays (IrOx NAs) were synthesized by electrodeposition with TiO2 nanotube arrays (TNTA) as template. By tuning the scan rate in the electrodeposition process, IrOx open-end nanotube arrays with tunable length ranged from 500 nm to 1400 nm and hollow nanorod arrays were obtained due to a diffusion-controlled deposition process. By constructing 3-D electrode of 1-D catalyst with enhanced ion transfer, IrOx NAs performed almost the same current density of OER with 1/20 Ir loading amount compared with commercial IrO2 nanoparticles, which could significantly reduce the cost of catalyst in PEM water electrolyser. Moreover, no apparent current decrease was observed even after 10 h' anodic polarization under 1.55 V, which exhibit excellent OER durability.