Unveiling the effects of oxygen doping on two-dimensional GaN for the sulfur reduction reaction in lithium-sulfur...

The presence of oxygen in bulk GaN, whether from intentional or unintentional doping, has been widely studied. However, the impact of oxygen doping on two-dimensional (2D) GaN as a sulfur host in Li-S batteries, particularly for mitigating the shuttle effect, remains largely unexplored. Herein, we use first-principles calculations to systematically evaluate the sulfur reduction reaction (SRR) on oxygen-doped 2D GaNs. Four doping configurations are considered: substitutional single-atom oxygen at Ga or N sites and interstitial oxygen in monoatomic (O) and diatomic (O₂) forms. We find that lithium polysulfides anchor strongly to oxygen-doped 2D GaN, with solvation exerting minimal influence on anchoring strengths. Interstitial oxygen doping lowers the Li₂S decomposition barrier by 0.22 eV compared to the pristine 2D GaN. The lowering of the decomposition barrier is attributed to the elongation of the Li-S bond, higher charge transfer and moderate binding energy of Li₂S on the 2D GaN. These results highlight that oxygen-doped 2D GaN is a promising anchoring material for lithium polysulfides and an efficient SRR electrocatalyst for Li-S batteries.