Tailoring ferroelectric polarization in In 2 Se n S 3− n monolayers via Se/S ratio modulation to boost polysulfide electrocatalysis

The commercialization of lithium-sulfur (Li-S) batteries is hindered by the polysulfide shuttle effect and slow sulfur redox kinetics. This study employs first-principles calculations to investigate the atomic-scale tuning of the selenium/sulfur ratio in two-dimensional ferroelectric In₂Se_nS_3-n monolayers, aiming to enhance the built-in electric field and electrocatalytic activity. The results show that out-of-plane polarization increases with increasing sulfur content. In₂S₃ shows the largest work function difference (ΔΦ = 1.08 eV), due to sulfur's higher electronegativity, which promotes polysulfide adsorption and conversion. However, In₂SeS₂ achieves the best balance among adsorption strength, conversion kinetics, and Li diffusion barriers. Mechanistic analysis attributes this performance to the critical role of localized, polarized surface charge distributions. External electric field simulations confirm that the strength of polarization directly influences polysulfide adsorption. This work establishes a clear "composition → polarization → adsorption/electrocatalysis" relationship, underscoring how ferroelectric polarization regulates polysulfide behavior and offering a design strategy for Li-S batteries.