ИСТИНА

Oxygen reduction reactions are heavily involved in various energy-related processes ranging from cell respiration in living organisms to electric power production in fuel cells and metal-air batteries. In contrast to ORR in aqueous solutions, oxygen reduction in non-aqueous media is much less investigated. The lack of such knowledge hinders the development of some new technologies, including so much desired lithium-air batteries that are capable to deliver few times higher specific energy in comparison with lithium-ion ones. Here we employ in situ near ambient pressure photoemission spectroscopy as a unique surface sensitive tool to probe oxygen reduction chemistry and concomitant processes occurring at the electrochemical interfaces of carbonaceous and some binary inorganic materials for Li-air positive electrodes. While the most Li-air batteries reported in literature utilize carbon as the positive electrode, we find that it is intrinsically unstable due to its reactivity towards superoxide species, which are produced as ORR intermediates. Side processes and irreversible electrode consumption is also detected for some alternative materials such as titanium carbide. These side reactions were found to produce carbonates that in turn limits the rechargeability.