Iridium nanoparticles anchored on 3D graphite foam as a bifunctional electrocatalyst for excellent overall water splitting in acidic solution

The proton-exchange-membrane (PEM) water-splitting electrolyser is a highly appealing technology for economical hydrogen production. Unfortunately, only Iridium (Ir)-based electrocatalysts show efficient and stable activity towards oxygen evolution reaction (OER) in acidic medium, which seriously hampers the large-scale utilization of PEM water splitting electrolyser as a result of high cost and scarcity of the Ir. Here, we report synthesis of Ir nanoparticles on 3D graphite foam (Ir/GF) upon a heat treatment of Ir³⁺/polyaniline complex that were beforehand prepared on the GF. Benefiting from low content of Ir (5.91 wt%) and excellent resistance of 3D graphite foam against oxidative corrosion, the resultant Ir/GF functionalizes as a novel bifunctional electrocatalyst for overall water splitting in a 0.5 M H₂SO₄ solution. Noticeably, the HER and OER overpotentials of the Ir/GF at 10 mA/cm² are only ~ 7 mV and ~ 290 mV, respectively, which are much lower than those of commercial Pt/C and Ir/C catalysts as well as reported Pt or Ir-based electrocatalysts. Significantly, an acidic water-splitting electrolyser with a current density of 10 mA/cm² is steadily driven by the Ir/GF at a cell voltage of only ~ 1.55 V, which is substantially lower than 1.65 V for commercial Pt/C and Ir/C couple.