M4B6X6 as a New Family of High‐Efficient Electrocatalysts: The Role of Surface Reconstruction in Water Oxidization

Searching for highly‐efficient electrocatalysts for water splitting has been greatly endowed due to the huge demand for green energy sources. Two‐dimensional (2D) materials are widely explored for the purpose because of their unique physical and chemical properties, abundant active sites, and easy fabrication. Here, we present a new family of 2D M4B6X6 (2D Boridenes) and investigate their physical and chemical properties for their potential applications into electrocatalysis based on first‐principles calculations. We demonstrate that 2D M4B6X6 (M=Cr, Mo, and W; X=O and F) are dynamically, thermodynamically, and mechanically stable, and show intriguing electronic and catalytic properties. Importantly, we find that M4B6O6 are intrinsically active for oxygen evolution reaction (OER). Our results demonstrate that: (1) the adsorbate‐escape mechanism dominates the OER process with a low overpotential of 0.652 V on Cr4B6O6; (2) the partial surface‐oxidization can improve the catalytic performance of M4B6F6 dramatically; and (3) the surface reconstruction greatly affects the OER performance of M4B6X6. Our findings illustrate that the surface reconstruction is critical to the OER activity, which may provide a new strategy on the design of 2D materials for electrocatalysis and offer theoretical insight into the catalytic mechanism. How surface reconstruction works: Based on the experimental results, a new kind of 2D borides (M4B6X6) is designed, which shows rich structures and amazing electronic properties. The surfaces of the 2D materials are reconstructed in the OER process. The OER overpotential of surface‐reconstructed Cr4B6O6 is only 0.652 eV. The partial oxidized M4B6F6 (M4B6F5O) shows highly improved OER performance than M4B6F6.