The question of whether glass continues to relax at low temperature is of fundamental and practical interest. Here, we report a novel atomistic simulation method allowing us to directly access the longterm dynamics of glass relaxation at room temperature. We find that the potential energy relaxation follows a stretched exponential decay, with a stretching exponent β = 3/5, as predicted by Phillips' diffusion-trap model. Interestingly, volume relaxation is also found. However, it is not correlated to the energy relaxation, but is rather a manifestation of the mixed alkali effect.

In interfacial charge-transfer reactions, the complexity of the reaction pathway increases with the number of charges transferred, and becomes even greater when the reaction involves both electrons (charge) and ions (mass). These so-called mixed ion electron transfer (MIET) reactions are crucial in intercalation/insertion electrochemistry, such as those occurring in oxygen reduction/evolution electrocatalysts and lithium-ion battery electrodes. Understanding MIET reaction pathways, particularly identifying the rate-determining step (RDS), is crucial for engineering interfaces at the molecular, electronic, and point defect levels. Here we develop a generalizable experimental and analysis framework for constructing the O 2 (g) incorporation reaction pathway in Pr 0.1 Ce 0.9 O 2-x. We converge on four candidate RDS (dissociation of neutral 31 oxygen adsorbate) out of more than 100 possibilities by measuring the current density-32 overpotential curves while controlling both oxygen activity in the solid and the oxygen gas 33 partial pressure, and quantifying the chemical and electrostatic driving forces using operando 34 ambient pressure X-ray photoelectron spectroscopy. 35 36 3 Mixed ion and electron transfer (MIET) reactions involve the transfer of both ionic and electronic charges across interfaces. They are substantially more complex than electron transfer and proton-coupled electron transfer reactions because the ionic charge also crosses the electrochemical double layer. 1 The net reactions are usually chemical in nature (i.e., no net charge transfer). Examples include H + intercalation in layered hydroxides and Li + insertion in 41 metal oxides (Fig. 1a,b). 2 Another ubiquitous example is the oxygen incorporation reaction (OIR) 42 occurring at the solid/gas interface (Fig. 1c). It is rate-determining for many energy-and 43 environment-related technologies, including oxygen storage materials for emission control, 3 44 solid oxide fuel cells (SOFCs), 4 electrolysis cells, 5 thermochemical water splitting cycles, 6 and oxygen permeation membranes. 7 The OIR is expressed as − − + → 2 2 O 4e 2O. (1) 47 Understanding the OIR reaction pathway is crucial for engineering and discovering catalysts, 48 typically oxides, with high activity and stability. 8,9 Mixed ionic-electronic conductors (MIECs) 49 have received widespread interests because they expand the effective OIR site to the gas/solid 50 double-phase boundary beyond the traditional triple phase boundary between gas, ionic and 51 electronic conductors. 10,11 There, oxygen ions and electrons react with oxygen adsorbates at the same active site, resulting in a reaction that involves the transfer of two oxygen ions and four electrons. The number of charges transferred during OIR has made it challenging to isolate the ratedetermining step (RDS). Most experimental work has focused on measuring the exchange coefficients 12 using tracer diffusion, 13 conductivity and mass relaxation, 14 and impedance spectroscopy, 15 as well as their reaction order with respect to oxyge...

Simultaneously achieving high activity and stability is the primary challenge when engineering (electro)­catalysts. Transition metal perovskite oxides are employed as air electrodes for solid-oxide fuel cells and electrolyzers. However, degradation of oxygen exchange kinetics at the solid–gas interface, often linked to alkaline-earth cation segregation and precipitation, limits widespread commercialization. In this work, we systematically investigated the surface degradation mechanism induced by gas-phase impurities in (La0.5Sr0.5)­FeO3−δ (LSF55) thin-film electrodes by varying the concentration of H2O, SO2, and CO2. Degradation of the area-specific resistance in ambient and humidified synthetic air is significantly greater than in dry ambient and dry synthetic air, pointing to the importance of water vapor. Time-resolved, in situ ambient pressure X-ray photoelectron spectroscopy performed in O2 showed that nonbulk Sr is present on the surface before the exposure to water vapor. Upon introduction of water vapor, neither additional Sr segregation nor precipitation driven by water vapor is a necessary condition for degradation. Rather, hydroxylation of the surface induces irreversible and significant degradation. At the same time, we show that Sr migration driven by water vapor is partially reversible. These fundamental insights can be used for the rational design of electrodes with improved catalytic stability.

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