Understanding the Electrocatalytic Trend of Sulfur Reduction Reaction and Design Rules of Advanced Electrocatalysts for Li-S Batteries.

Despite the great potential of using electrocatalysts to improve the performance of lithium-sulfur (Li-S) batteries, a deficient understanding of the electrocatalytic trends in the sulfur reduction reaction with respect to the adsorption energy of sulfur active species and a lack of descriptors to estimate electrocatalytic activity limit the design of advanced electrocatalysts for Li-S batteries. Herein, we systematically explore the impact of sulfur species adsorption energy on the electrocatalytic activity in Li-S batteries by modulating the metal d-band structure of Pt3M (M = Cu, Fe, Ti, Co) alloy model systems. The Pt3Co catalyst, possessing a balanced d-band center, exhibited the highest redox kinetics and Li-S cell performance due to its lowest energy barrier for the rate-determining step in the sulfur reduction reaction. Furthermore, the adsorption energies of sulfur (S) and lithium (Li) single atoms can offer deeper insights into the electrocatalytic activity in Li-S electrochemistry, indicating their great potential as descriptors to develop advanced electrocatalysts. The volcano-type correlation of the d-band center and descriptor with the kinetics of the sulfur reduction reaction highlighted that moderate adsorption of Li and S on the catalyst surface with a balanced d-band center is the key to achieving optimal Li-S battery performance. This work emphasizes the importance of tailoring the surface properties and electronic structures of the electrocatalyst according to the intrinsic characteristics of electrocatalysts.