electrodepositing Cu, Ni and Co. A combination of operando X-ray absorption spectroscopy and potentiometric control under aqueous conditions revealed the trends in reactivity yielded by these electrodes, which are directly associated with the cross-and overpotentials as well as the occupancy of the 3d orbitals. It was found that under anodic polarization the materials electrodeposited on gold suffer from a lack of stability, while under cathodic polarization they exhibit stable behavior. The observed activity is strongly related to the lack of stability shown by these composites under anodic polarization revealing a dynamic process ruled by corrosion. By operando X-ray absorption, we established that the overall enhancement of the activity for the oxygen evolution reaction is directly attributable to the cross-potential and corrosion process of the electrodeposited materials. It is associated with the high potential deposition, which is the origin of the incipient oxidation-corrosion resistance of the lattice.We conclude that the observed trends in the total current are directly associated with the loss of oxygen in the metal-oxide lattice and the subsequent dissolution of metallic ions in the electrolyte under anodic polarization.reacted O prevents a sustainable catalytic process. The addition of a small amount of metal-oxide, such as titanium or cerium oxides, on top of the Au surface facilitates this rate-determining step and easily continues the catalytic cycle of the production of O2. D e s p i t e t h i s a c t i v a t i o n s t r a t e g y b u l k A u i s a v e r y p o o r c a t a l y s t , b u t A u nanoparticles on metal oxide [3] and carbide [4] materials show unusual catalytic properti es. For exam ple, i t has been shown that CeO2 NPs sm aller than 10 nm dispersed on Au are an excellent catalyst for the water gas shift reaction [5]. In addition, controlling the partial coverage of Au with TiO2 or CeO2 enhances the catalytic activity [6]. Thus, role of size of different Au NPs has been shown as important factor in the catalytic activity [7]. Ideally, one can take advantage of these phenomena and develop highly efficient catalysts by optimizing the Au/metal-oxide synergy. Electrodeposition is an attractive method used to deposit a large variety of materials [8] and allows for precise control of the chemical composition and the structure of the electrodeposited material. However, not all the materials can be electrodeposited in aqueous environment like the alkali metals. Decoding the structure of the electrodeposited electrode, requires the use of advanced spectroscopic methods capable of providing detailed information about the electronic structure of polarized solid-liquid interfaces [9]. Ex-situ s tu di es a r e u n ab l e to d e s c ri b e s u ch complex electrochemical processes since the chemical reactions are often rather unique and cannot be "quenched" and investigated by "post-mortem" studies [10]. X-ray spectroscopy is a powerful element specific technique that allows for an unequivocal assignm...

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Ambient aging has substantially hindered the development of electronic and optoelectronic devices made of two-dimensional (2D) semiconducting layered materials because the origin of oxidation, degradation, and aging effects remains largely unexplored. This study unveils the mechanism and process of ambient aging in 2D-layered GaSe crystals by exploring the evolution of the ambient aging process in a snapshot fashion. Through the detailed examinations on surface morphology, lattice structure, and elemental compositions, three major stages of the aging process in GaSe crystals are identified: the formation of a defective GaSe top layer, a crystalline Ga 2 Se 3 layer, and an amorphous Ga 2 O 3 layer evolving on top of the Ga 2 Se 3 layer. In particular, it is suggestive that the formation of the crystalline Ga 2 Se 3 layer plays a crucial role in the entire oxidation process. The present results may be also applicable to other 2D semiconducting layered materials.

YMnO3 (YMO) thin film is one of the highly studied multiferroic materials due to its tunable crystalline structure via misfit strain from the substrate. This tunability involves intriguing physical phenomena that encourage further explorations for fundamental research and practical applications. The configuration of the initial atomic layers during the growth of YMO thin films plays a key role in determining their physical properties. In the present research, the correlation between the substrate’s polarity and the misfit strain of the YMO films is studied comprehensively. The results showed that despite the YMO films grown on MgO (100) and MgO (111) being under the same growth conditions and having resulted in the same hexagonal crystal structure (h-YMO), the films do exhibit distinctly different microstructures, electronic structures, and magnetic properties. We suggest that the extent of charge accumulation induced by the surface polarity of the substrates may have resulted in a substantially different intermixing feature at the h-YMO/substrate interfaces, which, in turn, alters the structure and thus the physical properties of the films. Our results open up the possibility of manipulating the h-YMO thin film’s magnetic properties by interfacial engineering without significantly altering the structure of the films which could benefit the fabrication efficiency for various next-generation electronics.