High-density growth of ultrafine PdIr nanowires on graphene: reducing the graphene wrinkles and serving as efficient bifunctional electrocatalysts for water splitting

Manipulating the space distribution states, exposed surfaces, and interfacial interactions of graphene-based nanomaterials is a key strategy for taking full advantage of graphene's characteristics. Herein, we report the in situ deposition of numerous ultrafine PdIr alloy nanowires (diameter of 1.8 nm) to predominately cover the entire surface of graphene (PdIr UNWs/WFG). The high density but low atom loading (8.6 at%) of PdIr nanowires gives rise to abundant edge atoms and a rough surface, which are beneficial for the full exposure of active sites. Meanwhile, the compact PdIr overlay provides strong surface tension to stretch the graphene wrinkles, thus averting the wrapping of active sites and ensuring structural uniformity. The PdIr UNWs/WFG are qualified as efficient and robust electrocatalysts in both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), affording 10 mA cm-2 at an HER overpotential of 23 mV and 10 mA cm-2 at an OER overpotential of 290 mV, respectively. The corresponding water electrolyzer requires a cell voltage of only 1.51 V to achieve a water-splitting current density of 10 mA cm-2. This simple and novel approach for studying the coordinated form, dispersion state, and interfacial tension is promising to be a versatile method for improving the properties of graphene-based nanomaterials.