An endstation for resonant inelastic X-ray scattering studies of solid and liquid samples.

A novel experimental setup is presented for resonant inelastic X-ray scattering investigations of solid and liquid samples in the soft X-ray region for studying the complex electronic configuration of (bio)chemical systems. The uniqueness of the apparatus is its high flexibility combined with optimal energy resolution and energy range ratio. The apparatus enables investigation of chemical analyses, which reflects the chemical imprints. The endstation is composed of a main sample chamber, a sample holder for either solid or liquid jet delivery system, and a soft X-ray grating spectrometer for 210–1250 eV with a resolving power of 1000. It combines for the first time liquid jet technology with a soft X-ray spectrometer based on the variable line spacing principle. This setup was commissioned at the soft X-ray beamline P04 at PETRA III of the Deutsches Elektronen-Synchrotron in Hamburg which is currently the most brilliant storage-ring-based X-ray radiation source in the world. The first results of liquid and solid samples show that this setup allows the detection of photons across an energy range of 300 eV. This covers simultaneously the emission lines of life- important elements like carbon, nitrogen and oxygen in a shot-based procedure

Contrasting Pr1 xCaxMnO3 OER Catalysts with Different Valences and Covalences

Perovskite oxides are promising materials for catalyzing the oxygen evolution reaction OER . However, understanding the properties of active sites that enable high OER activity without corrosive electrode reduction is still elusive. In this work, we use combined electrochemical and environmental transmission electron microscopy ETEM studies to compare the OER stability of the 001 surfaces of Pr1 xCaxMnO3 perovskite films with doping of x 0.1 and x 0.33. Notably, electrochemical analysis in alkaline conditions, as well as ETEM studies in H2O vapor, shows parallel trends in the stability of both systems Mn leaching for the Pr1 xCaxMnO3 PCMO x 0.33 system due to oxygen vacancy formation at the surface and higher stability of PCMO x 0.1, where the oxygen vacancy redox peak is absent in cyclovoltammetry. Electron energy loss spectroscopy reveals the preservation of the Mn valence state in H2O for the PCMO x 0.1 system, whereas for x 0.33, Mn is reduced. We interpret this enhanced stability for the low doped system in terms of a modified Mn 3d O 2p hybridization, i.e., covalence. For a system with charge localization due to Jahn Teller polarons, the covalence determines to what degree redox processes of lattice oxygen can arise that can finally lead to corrosive oxygen vacancy formatio

Environmental TEM Study of Electron Beam Induced Electrochemistry of Pr0.64Ca0.36MnO3 Catalysts for Oxygen Evolution

Environmental transmission electron microscopy (ETEVI) studies offer great potential for gathering atomic scale information on the electronic state of electrodes in contact with reactants. It also poses big challenges due to the impact of the high energy electron beam. In this article, we present an ETEM study of a Pr0.64Ca0.36MnO3 (PCMO) thin filth electrocatalySt for water splitting and Oxygen evolution in contact with water vapor: We show by means of off-axis electron holography and electrostatic modeling that the electron beam gives rise to a positive electric sample potential due to secondary electron emission. The value of the electric potential depends on the primary electron flux, the sample's electric Conductivity and grounding, and gas properties. We present evidence that two observed electrochemical reactions are driven by a beam induced electrostatic potential of the order of a volt. The first reaction is an anodic oxidation of oxygen depleted amorphous PCMO which results in recrystallization of the oxide. The Second reaction is oxygen evolution which can be detected by the oxidation of a silane additive and formation of SiO2-gamma at catalytically active surfaces. The quantification of beam induced potentials is an important step for future controlled electrochemical experiments in an ETEM

Probing the Surface of La0.6Sr0.4MnO3 in Water Vapor by In Situ Photon In Photon Out Spectroscopy

Resonant inelastic X ray scattering RIXS is a promising method for elucidating detailed electronic structure of materials in a broad range of chemical and physical applications. Here, we use the fine fluorescence energy resolution of a RIXS spectrometer to obtain various proxies of the Mn L edge X ray absorption spectra XAS of the perovskite La0.6Sr0.4MnO3 LSMO as a model catalyst for the oxygen evolution reaction OER and evaluate the suitability for in situ surface studies of this electrocatalyst. We conclude that the inverse partial fluorescence yield IPFY of the O 2p 1s transition and the partial fluorescence yield of the 3s 2p transition 3s PFY are most suitable for determining changes at the surface of the perovskite, because distortions at grazing incidence measurements are low. In particular, the negligible angular dependence of the 3s PFY spectra can be perfectly simulated using a fluorescence model in the thin sample limit which is justified by low reabsorption of 3s photons. Remarkably, the 3s PFY reveals an influence of water vapor on the electronic reconstruction of the LSMO surface. Thus, our work paves the road for quantitative distortion free X ray spectroscopy of transition metal oxide surfaces under in situ conditions, which is needed to understand fundamental chemical processes such as corrosion and catalysi