Transition Metal-Doped 2D GaN as Single-Atom Electrocatalysts for Lithium–Sulfur Batteries: Insights from First-Principles Calculations

Abstract

The commercial adoption of lithium–sulfur (Li–S) batteries is primarily limited by the shuttle effect and slow kinetics of the sulfur reduction reaction (SRR), which involves a complex 16-electron conversion process. Single-atom catalysts (SACs) show great potential as electrocatalysts to improve reaction kinetics in Li–S batteries. Using first-principles methods, we conducted computational screening of a series of transition metal (TM) atoms doped into two-dimensional (2D) GaN to enhance the SRR activity. Our results indicate that the important SRR step which involves liquid–solid transformation of Li₂S₄ into Li₂S is correlated linearly with the SRR overpotential via 2.7ΔG_Li2S* – ΔG_Li2S4^*. Based on the volcano plot, two catalysts, namely Pd@GaN and Cu@GaN, are identified as the most effective electrocatalysts, with an overpotential of 0.43 V. These doped atoms remain stable on the 2D GaN even at high temperatures. In addition, both Pd@GaN and Cu@GaN exhibit strong binding energies for high order Li₂S_n (n = 4, 6, 8), ranging from −1.81 to −2.99 eV, effectively mitigating the shuttle effect. This study offers theoretical insights into the SRR mechanism on TM-doped 2D GaN and guides the rational design of single-atom catalysts (SACs) for Li–S batteries.