Superior overall water splitting electrocatalysis in acidic conditions enabled by bimetallic Ir-Ag nanotubes

The development of efficient bifunctional electrocatalysts for overall water splitting in acidic condition is of importance for polymer electrolyte membrane (PEM) electrolyzers, but full of challenges. Herein, we report the successful creation of a class of hollow iridium (Ir)-silver (Ag) nanotubes (NTs) via a facile selective etching approach. Because of the unique properties of hollow structure and enriched oxidized Ir on the surface, the optimized Ir6Ag9 NTs show low oxygen evolution reaction overpotentials of 285 mV and 296 mV at 10 mA/cm(2) in 0.5 M and 0.05 M H2SO4, respectively, being superior to the commercial Ir/C. The Ir6Ag9 NTs also exhibit lower hydrogen evolution reaction overpotentials (only 20 mV and 34 mV at 10 mA/cm(2) in 0.5 M and 0.05 M H2SO4, respectively). More significantly, the Ir6Ag9 NTs/C can be further applied as bifunctional electrocatalysts with very low cell voltage of only 1.55 V at 10 mA/cm(2) in 0.5 M H2SO4 as well as excellent durability with very small activity loss after 1000 cycles, holding much potential in the practical application in proton exchange membrane water electrolyzer.