Atomically ordered Ir3Ti intermetallics for pH-universal overall water splitting

Abstract

Developing an efficient bifunctional electrocatalyst for overall water splitting under all pH conditions is challenging. Iridium (Ir)-based materials are promising electrocatalysts, but the high cost and limited reserves of Ir restrict their widespread applications. Alloying Ir with 3d transition metals to produce ordered intermetallic compounds (IMCs) is a well-established strategy aimed at diminishing the reliance on Ir and enhancing electrocatalytic activity. In this work, we synthesize Ir₃Ti IMCs on carbon nanotubes (i.e. Ir₃Ti/CNT), which exhibit remarkable performances in both the HER and OER across a broad pH range. Specifically, Ir₃Ti/CNT as both the anode and cathode delivers a current density of 10 mA cm⁻² at low cell voltages of 1.51 V and 1.52 V in 0.5 M H₂SO₄ and 1.0 M KOH, respectively. The density functional theory (DFT) calculations further demonstrate that alloying Ir with Ti atoms establishes the electron-rich environment for Ir atoms and regulates the adsorption energy of reaction intermediates on the surface of Ir₃Ti IMCs. Consequently, the energy barriers for overall water splitting are reduced and the electrocatalytic activities are improved. This study presents a compelling strategy for constructing advanced noble metal-based electrocatalysts with high efficiency, long-term stability, and pH-universality for overall water splitting.