Reversible polarization-enabled hydrogen evolution reaction on two-dimensional ferroelectric Cu _n (CrSe₂) _n+1...

The scalable production of hydrogen through electrochemical water splitting demands earth-abundant catalysts with both high activity and dynamic tunability, yet achieving these attributes simultaneously remains a major challenge. Two-dimensional (2D) ferroelectric materials offer a unique opportunity, as their reversible polarization can modulate surface electronic states, though their potential in electrocatalysis has scarcely been explored. Here, we employ first-principles calculations to investigate the electronic structure and hydrogen evolution reaction (HER) activity of recently synthesized Cu _n (CrSe₂) _n+1 (n = 1-3) monolayers with tunable thickness and robust multiferroic behavior at room temperature. We identify surface Se top sites as the optimal catalytic centers, with the down-polarized state exhibiting HER activity comparable to that of benchmark Pt(111). A strong inverse correlation between hydrogen adsorption free energy and the p-band center of surface Se atoms is further established, providing a predictive descriptor for catalyst design. Crucially, reversible polarization dynamically modulates hydrogen adsorption energetics through charge redistribution, enabling efficient transitions between H adsorption and H₂ desorption and thereby maximizing HER efficiency. These insights position Cu _n (CrSe₂) _n+1 as a promising polarization-switchable platform for high-performance and controllable electrocatalysis, offering general design principles for next-generation ferroelectric catalysts.