Real time in-situ microscopy imaging of surface structure and atom dynamics of heterogeneous catalysts is an important step for understanding reaction mechanisms. Here, using in-situ environmental transmission electron microscopy (ETEM), we directly visualize surface atom dynamics at manganite perovskite catalyst surfaces for oxygen evolution reaction (OER), which are ≥20 times faster in water than in other ambients. Comparing (001) surfaces of La_0.6Sr_0.4MnO₃ and Pr_0.67Ca_0.33MnO₃ with similar initial manganese valence state and OER activity, but very different OER stability, allows us to distinguish between reversible surface adatom dynamics and irreversible surface defect chemical reactions. We observe enhanced reversible manganese adatom dynamics due to partial solvation in adsorbed water for the highly active and stable La_0.6Sr_0.4MnO₃ system, suggesting that aspects of homogeneous catalysis must be included for understanding the OER mechanism in heterogeneous catalysis.

A method for enhancing the photoluminescence of silicon nanocrystals in a silicon oxide matrix by fabrication of periodic surface structures through laser irradiation is demonstrated. ArF excimer lasers are used to produce periodic line structures by material ablation. Photoluminescence, Raman, and transmission electron microscope measurements consistently show the formation of crystalline silicon after high-temperature annealing. A 2.6-fold enhancement of photoluminescence signal is measured for a periodic line structure with 600 nm period. The influence of a surface structure on the photoluminescence from the silicon oxide layer is discussed in terms of a simple model describing the main effect.

Superlattices (SLs) comprising layers of a soft ferromagnetic metal La_2/3Sr_1/3MnO₃ (LSMO) with in-plane (IP) magnetic easy axis and a hard ferromagnetic insulator La₂MnCoO₆ (LMCO, out-of-plane anisotropy) were grown on SrTiO₃ (100)(STO) substrates by a metalorganic aerosol deposition technique. Exchange spring magnetic (ESM) behavior between LSMO and LMCO, manifested by a spin reorientation transition of the LSMO layers towards perpendicular magnetic anisotropy below T_SR = 260 K, was observed. Further, 3ω measurements of the [(LMCO)₉/(LSMO)₉]₁₁/STO(100) superlattices revealed extremely low values of the cross-plane thermal conductivity κ(300 K) = 0.32 Wm⁻¹K⁻¹. Additionally, the thermal conductivity shows a peculiar dependence on the applied IP magnetic field, either decreasing or increasing in accordance with the magnetic disorder induced by ESM. Furthermore, both positive and negative magnetoresistance were observed in the SL in the respective temperature regions due to the formation of 90°-Néel domain walls within the ESM, when applying IP magnetic fields. The results are discussed in the framework of electronic contribution to thermal conductivity originating from the LSMO layers.

Despite significant advancements in materials design for renewable energy devices, the fundamental understanding of the underlying processes in many materials remains limited, particularly in complex, inhomogeneous systems and interfaces. In such cases, in situ studies with high spatial and energy resolution are essential for uncovering new insights into excitation, dissipation, and conversion processes. Recent progress in in situ atomic scale methods has greatly enhanced the understanding of energy materials. Here, key advances are reviewed, including in situ, environmental and ultra‐fast transmission electron microscopy, scanning probe techniques, single‐photon‐resolved infrared spectroscopy, velocity‐resolved molecular kinetics, and in situ grazing‐incidence X‐ray spectroscopy. These techniques enable the study of energy conversion with spatial resolution from nanometers down to individual atoms, energy resolution down to meV, and single‐quantum detection. Especially they enable access to processes that involve multiple degrees of freedom, strong coupling, or spatial inhomogeneities. They have driven a qualitative leap in the fundamental understanding of energy conversion processes, opening new avenues for improving existing materials and designing novel clean and efficient energy materials in photovoltaics, friction, and surface chemistry and (photo‐)electrochemistry.

Advanced interface engineering provides a way to control the ground state of correlated oxide heterostructures, which enables the shaping of future electronic and magnetic nanodevices with enhanced performance. An especially promising and rather new avenue is to find and explore low-dimensional phases of structural, ferroic and superconducting origin. In this multimodal study, we present a novel dynamic growth control method that enables the synthesis of compositionally graded superlattices (SLs) of (LaMnO₃)₁₀/(SrMnO₃)₁₀ (LMO/SMO), in which the layers gradually change their composition between LMO and SMO with gradient G values ranging from 0 to 100%. This leads to strong modulations in the material's electronic properties and of the two-phase ferromagnetic (FM) behavior. In particular, we observe that G surprisingly has almost no impact on the emergent high-temperature FM phase; in contrast, the low-temperature volume-like FM phase increases drastically with higher G-factors and thus can serve as a precise marker for chemical composition on a nanoscale. Focusing on the interfacial charge transfer found at sharp SMO/LMO interfaces (G = 0), we observe that for higher G-factors a long-range charge modulation develops, which is accompanied by an insulator-to-metal transition. These findings showcase G as a crucial control parameter that can shape a superlattice's intrinsic properties and provide a perspective for designing functional oxide heterostructures with artificially disordered interfaces.