We report a simple and effective electrochemical method to remove Fe impurities from commercial KOH electrolyte. We therefore utilize a MoS 2 catalyst deposited on porous Ni foam as both the anode and cathode in a two-electrode electrolysis setup. After 12 h of constant galvanostatic electrolysis at 100 mA, the Fe impurities from the KOH electrolyte were successfully removed, as confirmed by means of inductively coupled plasma optical emission spectroscopy analysis. In the purified KOH, a Ni−Co 3 O 4 composite oxide catalyst showed no Fe-induced activation. In contrast, we directly observed the uptake of Fe on the Ni−Co 3 O 4 catalyst from the nontreated electrolyte during catalyst operation using a coupled spectroelectrochemical setup. Interestingly, we further identified an influence on the dissolution behavior of Ni and Co in the presence of Fe impurities. Whereas hitherto mainly the activation effect of Fe impurities has been discussed, we hereby show that they additionally suppress corrosion under reaction conditions. Using our fast and low-cost method for the purification of large amounts of electrolyte, catalyst materials can be widely studied without these additional effects induced by Fe impurities in commercial KOH.

Manganese oxide (MnO x )electrocatalysts are examined herein by in situ soft X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS) during the oxidation of water buffered by borate (pH 9.2) at potentials from 0.75 to 2.25 Vv s. the reversible hydrogen electrode. Correlation of L-edge XAS data with previous mechanistic studies indicates Mn IV is the highest oxidation state involved in the catalytic mechanism. MnO x is transformed into birnessite at 1.45 Vand does not undergo further structural phase changes. At potentials beyond this transformation, RIXS spectra show progressive enhancement of charge transfer transitions from oxygen to manganese.T heoretical analysis of these data indicates increased hybridization of the Mn À Oo rbitals and withdrawal of electron density from the Oligand shell. In situ XAS experiments at the OK -edge providec omplementary evidence for such at ransition. This step is crucial for the formation of O 2 from water.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

Photons and electrons are two common relaxation products upon X-ray absorption, enabling fluorescence yield and electron yield detections for X-ray absorption spectroscopy (XAS).The ions that are created during the electron yield process are relaxation products too, which are exploited in this study to produce ion yield for XA detection. The ionic currents measured in a liquid cell filled with water or iron(III) nitrate aqueous solutions exhibit characteristic O K-edge and Fe L-edge absorption profiles as a function of excitation energy. Application of two electrodes installed in the cell is crucial for obtaining the XA spectra of the liquids behind membranes. Using a single electrode can only probe the species adsorbed on the membrane surface. The ionic-current detection, termed as total ion yield (TIY) in this study, also produces an undistorted Fe L-edge XA spectrum, indicating its promising role as a novel detection method for XAS studies in liquid cells.Key words: total ion yield (TIY), ionic current, liquid flow-cell, total electron yield (TEY), X-ray absorption spectroscopy (XAS) TOC GraphicPage 2 of 17 ACS Paragon Plus EnvironmentThe Journal of Physical Chemistry Letters 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 3 Studying the electronic structure of liquid water and aqueous solutions by soft X-rays has attracted much attention in recent years, 1-6 and continues to be a vital research field. Resonant excitation by X-rays is highly element-specific, which makes X-ray absorption spectroscopy (XAS) a widely used tool in many scientific disciplines. Due to the vacuum requirement for soft X-ray propagation, detection of XA spectra for liquid (volatile) samples in vacuum is very challenging. One of the most applied techniques to introduce liquid samples into a vacuum chamber is a liquid flow-cell with an ultra-thin membrane separating the liquid from the vacuum. 7,8 When equipped with multiple electrodes, such a liquid cell can act as a standard electrochemical cell. It is therefore of great interest to combine XAS and the liquid cell technique for in situ/operando investigations on liquid-based materials. [9][10][11][12] When a sample's thickness exceeds the penetration depth of soft X-rays, which is the case for the liquid cell adopted in this study, detection of XA spectra in the transmission mode is not applicable. Therefore, fluorescence yield (FY) or electron yield (EY) must be employed to acquire XA spectra. Due to the significant thickness of typical membranes, e.g. Si 3 N 4 and SiC membranes (~ 100 nm), the electrons created within liquid solutions cannot penetrate the membrane and escape into vacuum. The FY was thus considered the only feasible way to probe the liquid-phase species behind membranes. However, EY has been recently realized in liquid cell studies, thanks to the newly developed graphene membra...

The instability and expense of anodes for water electrolyzers with acidic electrolytes can be overcome through the implementation of a cobalt‐iron‐lead oxide electrocatalyst, [Co–Fe–Pb]Ox, that is self‐healing in the presence of dissolved metal precursors. However, the latter requirement is pernicious for the membrane and especially the cathode half‐reaction since Pb2+ and Fe3+ precursors poison the state‐of‐the‐art platinum H2 evolving catalyst. To address this, we demonstrate the invariably stable operation of [Co–Fe–Pb]Ox in acidic solutions through a cobalt‐selective self‐healing mechanism without the addition of Pb2+ and Fe3+ and investigate the kinetics of the process. Soft X‐ray absorption spectroscopy reveals that low concentrations of Co2+ in the solution stabilize the catalytically active Co(Fe) sites. The highly promising performance of this system is showcased by steady water electrooxidation at 80±1 °C and 10 mA cm−2, using a flat electrode, at an overpotential of 0.56±0.01 V on a one‐week timescale.