Decoration of Ir clusters accelerates the generation of active species for high-efficient overall water splitting

Noble metal decoration is one of the most efficient strategies to enhance the activity of electrocatalysts for hydrogen/oxygen evolution reaction (HER/OER). However, there is still lack of a comprehensive picture of how such strategy enhances the activity due to the complicated surface reconstructions and various electronic in-teractions on electrocatalysts during reactions, severely hampering the widespread utilizations of this strategy. Herein, we report that decorating Ir clusters on Fe doped Ni2P (Ir@Ni2P(Fe)) can reinforce the reconstruction of Ni2P(Fe) to generate more real active species via promoting the leaching of P element and ultimately improve the activities for both HER and OER. Specifically, such reinforcement leads to a considerably enhanced electron transfer and a substantially increased amount of active sites, ultimately playing a dominant role in boosting the HER performance from 176 mV over Ni2P(Fe) to 35 mV over Ir@Ni2P(Fe) at 10 mA cm-2. As for OER, in addition to increasing the amount of active sites via the reinforcement, the decoration of Ir clusters provides high-valence Ir sites as extra efficient active centers, thereby resulting in dual promotional effects to enhance the activity from 270 to 200 mV at 10 mA cm-2. Finally, using Ir@Ni2P(Fe) as both the anode and cathode, a low cell voltage of 1.50 V is required to derive a current density of 10 mA cm-2 for overall water splitting. The developed comprehensive insight is of clear significance to design advanced bifunctional electrocatalysts for overall water splitting.