Iridium–Tungsten Alloy Nanodendrites as pH-UniversalWater-Splitting Electrocatalysts

摘要

The development of highly efficient and durable electrocatalysts for high-performance overall water-splitting devices is crucial for clean energy conversion. However, the existing electrocatalysts still suffer from low catalytic efficiency, and need a large overpotential to drive the overall water-splitting reactions. Herein, we report an iridium–tungsten alloy with nanodendritic structure (IrW ND) as a new class of high-performance and pH-universal bifunctional electrocatalysts for hydrogen and oxygen evolution catalysis. The IrW ND catalyst presents a hydrogen generation rate ∼2 times higher than that of the commercial Pt/C catalyst in both acid and alkaline media, which is among the most active hydrogen evolution reaction (HER) catalysts yet reported. The density functional theory (DFT) calculations reveal that the high HER intrinsic catalytic activity results from the suitable hydrogen and hydroxyl binding energies, which can accelerate the rate-determining step of the HER in acid and alkaline media. Moreover, the IrW NDs show superb oxygen evolutionreaction (OER) activity and much improved stability over Ir. The theoreticalcalculation demonstrates that alloying Ir metal with W can stabilizethe formed active iridium oxide during the OER process and lower thebinding energy of reaction intermediates, thus improving the Ir corrosionresistance and OER kinetics. Furthermore, the overall water-splittingdevices driven by IrW NDs can work in a wide pH range and achievea current density of 10 mA cm^–2 in acid electrolyteat a low potential of 1.48 V.