Abstract

Understanding the reactivity of ubiquitous molecules on complex oxides has broad impacts in energy applications and catalysis. The garnet-type Li₇La₃Zr₂O₁₂ is a promising solid-state electrolyte for lithium(Li)-ion batteries, and it readily reacts with H₂O and CO₂ when exposed to ambient air. Such reactions form a contamination layer on Li₇La₃Zr₂O₁₂ that is detrimental to the battery operations. The strong interactions of Li₇La₃Zr₂O₁₂ with H₂O and CO₂, however, make Li₇La₃Zr₂O₁₂ a promising support to catalyze H₂O dissociation and CO₂ adsorption. Here, using first-principles calculations, we investigate the adsorption and reactions of H₂O and CO₂ on a Li₇La₃Zr₂O₁₂ surface. We show that H₂O reacts through the exchange of proton and Li+ and produces metal hydroxide species. At high H₂O coverage, half of the H₂O molecules dissociate while the other half remain intact. CO₂ reacts with the Li₇La₃Zr₂O₁₂ surface directly to produce carbonate species. We clarify that the individual reactions of H₂O and CO₂ with Li₇La₃Zr₂O₁₂ are more thermodynamically favorable than the co-adsorption of H₂O and CO₂. Finally, we demonstrate that low temperature and high partial pressure promote the reactions of H₂O and CO₂ with Li₇La₃Zr₂O₁₂. For energy storage application of Li₇La₃Zr₂O₁₂, our study guides processing conditions to minimize surface contamination. From a catalysis point of view, our findings reveal the potential of using complex oxides, such as Li₇La₃Zr₂O₁₂ as a support for reactions requiring H₂O dissociation and strong CO₂ adsorption.