Strong interaction-induced in situ-reconstructed Ag3 triangle as a real active unit for enhanced electrocatalytic hydrogen evolution

Due to the lack of well-defined structure, identifying and modulating structural reconstruction of a catalyst in reaction still remains a challenge. Herein, we prepared two atomically precise nanoclusters (Ag48 and Ag50) with almost the same size and cluster framework. Ag48 showed higher electrocatalytic hydrogen evolution reaction (HER) activity than Ag50 due to an in situ-reconstructed real active unit Ag3 triangle with appropriate hydrogen-binding energy. Based on in situ characterization and theoretical calculation, the structural reconstruction of Ag48 originated from the strong Ag-Ag interaction. Furthermore, two kinds of Ag4 NCs were targeted for synthesis. The Ag4 NC with stronger Ag-Ag interaction presented the Ag3 triangle and exhibited better HER performance than the linear-type Ag4 NC, validating the Ag3 triangle arising from the strong interaction was the key for high HER activity. This study highlights the fundamental mechanism of interaction-induced structural reconstruction, providing useful guidelines for the design of a highly efficient catalyst.