Photodegradation of CuBi2O4 Films Evidenced by Fast Formation of Metallic Bi using Operando Surface-sensitive X-ray Scattering**

CuBi₂O₄ has recently emerged as a promising photocathode for photo-electrochemical (PEC) water splitting. However, its fast degradation under operation currently poses a limit to its application. Here, we report a novel method to study operando the semiconductor-electrolyte interface during PEC operation by surface-sensitive high-energy X-ray scattering. We find that a fast decrease in the generated photocurrents correlates directly with the formation of a metallic Bi phase. We further show that the slower formation of metallic Cu, as well as the dissolution of the electrode in contact with the electrolyte, further affect the CuBi₂O₄ activity and morphology. Our study provides a comprehensive picture of the degradation mechanisms affecting CuBi₂O₄ electrodes under operation and poses the methodological basis to investigate the photocorrosion processes affecting a wide range of PEC materials.     

A Complete Triad of Zero-Valent 17-Electron Monoradicals of Group 7 Elements Stabilized by m-Terphenyl Isocyanides

The first consistent series of mononuclear 17-electron complexes of three Group 7 elements has been isolated in crystalline form and studied by X-ray diffraction and spectroscopic methods. The paramagnetic compounds have a composition of [M⁰(CO)(CNp-F-Ar^DArF2)₄] (M=Mn, Tc, Re; Ar^DArF2=2,6-(3,5-(CF₃)₂C₆H₃)₂C₆H₂F) and are stabilized by four sterically encumbering isocyanides, which prevent the metalloradicals from dimerization. They have a square pyramidal structure with the carbonyl ligands as apexes. The frozen-solution EPR spectra of the rhenium and technetium compounds are clearly anisotropic with large ⁹⁹Tc and ^185,187Re hyperfine interactions for one component. High-field EPR (Q band and W band) has been applied for the elucidation of the EPR parameters of the manganese(0) complex.     

The behavior of the structure function at large wavevectors for polymers in different regimes

Off‐lattice Monte Carlo simulations employing the pivot algorithm are used to generate ideal and excluded volume linear polymers in three dimensions. The structure function at large wavevectors is calculated from the resulting configurations. This is compared to the exact equation for ideal chains and to experimental data and both scaling and renormalization group predictions for excluded volume chains. It is found that using the des Cloizeaux form for the distance distribution function in an analytic calculation of the structure function leads to close agreement with the experimental and Monte Carlo data.