Showing papers on "Absorption spectroscopy published in 2018"

High-Density Ultra-small Clusters and Single-Atom Fe Sites Embedded in Graphitic Carbon Nitride (g-C3N4) for Highly Efficient Catalytic Advanced Oxidation Processes

Abstract: Ultra-small metal clusters have attracted great attention owing to their superior catalytic performance and extensive application in heterogeneous catalysis However, the synthesis of high-density metal clusters is very challenging due to their facile aggregation Herein, one-step pyrolysis was used to synthesize ultra-small clusters and single-atom Fe sites embedded in graphitic carbon nitride with high density (iron loading up to 182 wt %), evidenced by high-angle annular dark field-scanning transmission electron microscopy, X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, and 57Fe Mossbauer spectroscopy The catalysts exhibit enhanced activity and stability in degrading various organic samples in advanced oxidation processes The drastically increased metal site density and stability provide useful insights into the design and synthesis of cluster catalysts for practical application in catalytic oxidation reactions

Microporous Framework Induced Synthesis of Single-Atom Dispersed Fe-N-C Acidic ORR Catalyst and Its in Situ Reduced Fe-N4 Active Site Identification Revealed by X-ray Absorption Spectroscopy

Abstract: Developing highly efficient, low-cost oxygen reduction catalysts, especially in acidic medium, is of significance toward fuel cell commercialization. Although pyrolyzed Fe-N-C catalysts have been regarded as alternatives to platinum-based catalytic materials, further improvement requires precise control of the Fe-Nx structure at the molecular level and a comprehensive understanding of catalytic site structure and the ORR mechanism on these materials. In this report, we present a microporous metal–organic-framework-confined strategy toward the preferable formation of single-atom dispersed catalysts. The onset potential for Fe-N-C is 0.92 V, comparable to that of Pt/C and outperforming most noble-metal-free catalysts ever reported. A high-spin Fe3+-N4 configuration is revealed by the 57Fe Mossbauer spectrum and X-ray absorption spectroscopy for Fe L-edge, which will convert to Fe2+-N4 at low potential. The in situ reduced Fe2+-N4 moiety from high-spin Ox-Fe3+-N4 contributes to most of the ORR activity due t...

Bimolecular recombination in methylammonium lead triiodide perovskite is an inverse absorption process.

Abstract: Photovoltaic devices based on metal halide perovskites are rapidly improving in efficiency. Once the Shockley-Queisser limit is reached, charge-carrier extraction will be limited only by radiative bimolecular recombination of electrons with holes. Yet, this fundamental process, and its link with material stoichiometry, is still poorly understood. Here we show that bimolecular charge-carrier recombination in methylammonium lead triiodide perovskite can be fully explained as the inverse process of absorption. By correctly accounting for contributions to the absorption from excitons and electron-hole continuum states, we are able to utilise the van Roosbroeck-Shockley relation to determine bimolecular recombination rate constants from absorption spectra. We show that the sharpening of photon, electron and hole distribution functions significantly enhances bimolecular charge recombination as the temperature is lowered, mirroring trends in transient spectroscopy. Our findings provide vital understanding of band-to-band recombination processes in this hybrid perovskite, which comprise direct, fully radiative transitions between thermalized electrons and holes.

The Making and Breaking of Lead-Free Double Perovskite Nanocrystals of Cesium Silver-Bismuth Halide Compositions

Abstract: Replacing lead in halide perovskites is of great interest due to concerns about stability and toxicity. Recently, lead free double perovskites in which the unit cell is doubled and two divalent lead cations are substituted by a combination of mono- and trivalent cations have been synthesized as bulk single crystals and as thin films. Here, we study stability and optical properties of all-inorganic cesium silver(I) bismuth(III) chloride and bromide nanocrystals with the double perovskite crystal structure. The cube-shaped nanocrystals are monodisperse in size with typical side lengths of 8 to 15 nm. The absorption spectrum of the nanocrystals presents a sharp peak, which we assign to a direct bismuth s–p transition and not to a quantum confined excitonic transition. Using this spectroscopic handle combined with high-resolution transmission electron microscopy (TEM) based elemental analysis, we conduct stoichiometric studies at the single nanocrystal level as well as decomposition assays in solution and obs...

Light Absorption Coefficient of CsPbBr3 Perovskite Nanocrystals.

Abstract: Inductively coupled plasma mass spectrometry (ICP-MS) was combined with UV–vis absorption spectroscopy and transmission electron microscopy to determine the size, composition, and intrinsic absorption coefficient μi of 4 to 11 nm sized colloidal CsPbBr3 nanocrystals (NCs). The ICP-MS measurements demonstrate the nonstoichiometric nature of the NCs, with a systematic excess of lead for all samples studied. Rutherford backscattering measurements indicate that this enrichment in lead concurs with a relative increase in the bromide content. At high photon energies, μi is independent of the nanocrystal size. This allows the nanocrystal concentration in CsPbBr3 nanocolloids to be readily obtained by a combination of absorption spectroscopy and the CsPbBr3 sizing curve.

Nanoceria-Supported Single-Atom Platinum Catalysts for Direct Methane Conversion

Abstract: Nanoceria-supported atomic Pt catalysts (denoted as Pt1@CeO2) have been synthesized and demonstrated with advanced catalytic performance for the nonoxidative, direct conversion of methane. These catalysts were synthesized by calcination of Pt-impregnated porous ceria nanoparticles at high temperature (ca. 1000 °C), with the atomic dispersion of Pt characterized by combining aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analyses. The Pt1@CeO2 catalysts exhibited much superior catalytic performance to its nanoparticulated counterpart, achieving 14.4% of methane conversion at 975 °C and 74.6% selectivity toward C2 products (ethane, ethylene, and acetylene). Comparative studies of the Pt1@CeO2 catalysts with different loadings as well as the nanoparticulated counterpart reveal the single-atom Pt to be ...

First Theoretical Framework of Triphenylamine–Dicyanovinylene-Based Nonlinear Optical Dyes: Structural Modification of π-Linkers

Abstract: This work was inspired by a previous report [Janjua, M.R.S.A. Inorg. Chem. 2012, 51, 11306−11314] in which the nonlinear optical (NLO) response strikingly improved with double heteroaromatic rings. Herein, series of triphenylamine–dicyanovinylene based donor−π–acceptor dyes had been designed by structural tailoring of π-conjugated linkers and theoretical descriptions of their molecular NLO properties were reported. Density functional theory and time-dependent density functional theory calculations were performed on optimized geometries to elucidate the electronic structures, absorption spectra, and NLO properties and also to shed light on how structural modification influences the NLO properties. The simulated absorption spectra results indicate that all of the dyes showed the maximum absorbance wavelength in the visible region. The lowest unoccupied molecular orbital–highest occupied molecular orbital energy gaps of all of the dyes have been found smaller, which results in large NLO response. Calculation...

A universal approach for calculating the Judd–Ofelt parameters of RE3+ in powdered phosphors and its application for the β-NaYF4:Er3+/Yb3+ phosphor derived from auto-combustion-assisted fluoridation

Abstract: It is difficult to calculate the Judd-Ofelt (J-O) parameters for trivalent rare earth (RE)-doped powders due to the unavailable absorption spectrum that is necessarily used in the conventional J-O calculation procedure. In this study, a universal method starting from the diffuse-reflection spectrum for calculating the J-O parameters of RE3+-doped powdered samples was proposed. In this proposed method, by taking the Kubelka-Munk function into account, the absorption cross-section spectrum was derived from the diffuse-reflection spectrum in the RE3+-doped powdered sample using the connection between the absorption cross section and the radiative transition rate of RE3+. Then, the J-O parameters might be calculated from the absorption cross-section spectrum via the traditional J-O calculation technique. The NaYF4:Er3+/Yb3+ and NaYF4:Er3+ phosphors were prepared via an auto-combustion-assisted fluoridation technique, and the J-O calculation was carried out for the obtained samples. The obtained J-O parameters were compared with those reported in the literature and also verified by comparing the calculated radiative transition lifetimes with the experimental values. Finally, it was deduced that the proposed J-O calculation route was practicable.

Optical spectroscopy of laser-produced plasmas for standoff isotopic analysis

Abstract: Rapid, in-field, and non-contact isotopic analysis of solid materials is extremely important to a large number of applications, such as nuclear nonproliferation monitoring and forensics, geochemistry, archaeology, and biochemistry. Presently, isotopic measurements for these and many other fields are performed in laboratory settings. Rapid, in-field, and non-contact isotopic analysis of solid material is possible with optical spectroscopy tools when combined with laser ablation. Laser ablation generates a transient vapor of any solid material when a powerful laser interacts with a sample of interest. Analysis of atoms, ions, and molecules in a laser-produced plasma using optical spectroscopy tools can provide isotopic information with the advantages of real-time analysis, standoff capability, and no sample preparation requirement. Both emission and absorption spectroscopy methods can be used for isotopic analysis of solid materials. However, applying optical spectroscopy to the measurement of isotope ratios from solid materials presents numerous challenges. Isotope shifts arise primarily due to variation in nuclear charge distribution caused by different numbers of neutrons, but the small proportional nuclear mass differences between nuclei of various isotopes lead to correspondingly small differences in optical transition wavelengths. Along with this, various line broadening mechanisms in laser-produced plasmas and instrumental broadening generated by the detection system are technical challenges frequently encountered with emission-based optical diagnostics. These challenges can be overcome by measuring the isotope shifts associated with the vibronic emission bands from molecules or by using the techniques of laser-based absorption/fluorescence spectroscopy to marginalize the effect of instrumental broadening. Absorption and fluorescence spectroscopy probe the ground state atoms existing in the plasma when it is cooler, which inherently provides narrower lineshapes, as opposed to emission spectroscopy which requires higher plasma temperatures to be able to detect thermally excited emission. Improvements in laser and detection systems and spectroscopic techniques have allowed for isotopic measurements to be carried out at standoff distances under ambient atmospheric conditions, which have expanded the applicability of optical spectroscopy-based isotopic measurements to a variety of scientific fields. These technological advances offer an in-situ measurement capability that was previously not available. This review will focus on isotope detection through emission, absorption, and fluorescence spectroscopy of atoms and molecules in a laser-produced plasma formed from a solid sample. A description of the physics behind isotope shifts in atoms and molecules is presented, followed by the physics behind solid sampling of laser ablation plumes, optical methods for isotope measurements, the suitable physical conditions of laser-produced plasma plumes for isotopic analysis, and the current status. Finally, concluding remarks will be made on the existing knowledge/technological gaps identified from the current literature and suggestions for the future work.

Single-Shot Sub-microsecond Mid-infrared Spectroscopy on Protein Reactions with Quantum Cascade Laser Frequency Combs

Abstract: The kinetic analysis of irreversible protein reactions requires an analytical technique that provides access to time-dependent infrared spectra in a single shot. Here, we present a spectrometer based on dual-frequency-comb spectroscopy using mid-infrared frequency combs generated by quantum cascade lasers. Attenuation of the intensity of the combs by molecular vibrational resonances results in absorption spectra covering 55 cm-1 in the fingerprint region. The setup has a native resolution of 0.3 cm-1, noise levels in the μOD range, and achieves sub-microsecond time resolution. We demonstrate the simultaneous recording of both spectra and transients of the photoactivated proton pump bacteriorhodopsin. More importantly, a single shot, i.e., a single visible light excitation, is sufficient to extract spectral and kinetic characteristics of several intermediates in the bacteriorhodopsin photocycle. This development paves the way for the noninvasive analysis of enzymatic conversions with high time resolution, broad spectral coverage, and minimal sample consumption.

Enhanced photoluminescence in Tm3+, Yb3+, Mg2+ tri-doped ZnWO4 phosphor: Three photon upconversion, laser induced optical heating and temperature sensing

Abstract: Three photon upconversion photoluminescence has been observed in Tm3+, Yb3+ co-doped ZnWO4 phosphor synthesized through solid state reaction method. The structural measurements reveal an increase in crystallinity and particles size on Mg2+ incorporation. The EDS spectrum shows the presence of Zn, W, Tm, Yb, Mg and O elements in the phosphor. The UV–vis-NIR absorption spectra contain CTB and 4f-4f transitions due to Tm3+ and Yb3+ ions, respectively. The Tm3+, Yb3+ co-doped phosphor gives intense blue and NIR emissions alongwith a weak red emission due to 1G4→3H6, 3H4→3H6 and 1G4→3F4 transitions, respectively upon 976 nm excitation. The emission intensity of the phosphor is found optimum at 2 mol% concentration of Yb3+ ion. When the Mg2+ ion is incorporated in the co-doped phosphor, the emission intensity enhances upto two times. This may be due to improved crystal structure and an increase in the intensity of absorption bands. The FIR analysis in the Stark components of 1G4 level suggests an efficient optical heating and temperature sensing ability. The temperature sensing sensitivity is found to be 34 × 10−4 °K-1 at 300°K. Thus, the Tm3+, Yb3+, Mg2+ tri-doped ZnWO4 phosphor may be used in photonic devices, NIR source, as an optical heater and temperature sensor purposes.

High-throughput computational X-ray absorption spectroscopy

Abstract: X-ray absorption spectroscopy (XAS) is a widely-used materials characterization technique. In this work we present a database of computed XAS spectra, using the Green's formulation of the multiple scattering theory implemented in the FEFF code. With more than 500,000 K-edge X-ray absorption near edge (XANES) spectra for more than 40,000 unique materials, this database constitutes the largest existing collection of computed XAS spectra to date. The data is openly distributed via the Materials Project, enabling researchers across the world to access it for free and use it for comparisons with experiments and further analysis.

Facile synthesis of highly efficient ZnO/ZnFe2O4 photocatalyst using earth-abundant sphalerite and its visible light photocatalytic activity

Abstract: Micrometer-scale ZnO/ZnFe2O4 coupled photocatalyst is synthesized via a simple, one-step thermal treatment performing on natural Fe-bearing sphalerite ((Zn, Fe)S). In situ high-temperature X-ray diffraction (XRD), thermogravimetry, differential thermal analysis (TG/DTA) and scanning electron microscopy (SEM) results indicated that octahedral ZnFe2O4 (∼5 μm) formed on the surface of substrate-like ZnO (tens of microns) derived from the oxidation of sulfides upon heating to 800 °C in air for 1 h, and the two components kept stable phase ratio at 3:7 (wt%) from 900 °C (sample M-900) to 1200 °C (sample M-1200). X-ray absorption spectroscopy (XAS) and Raman spectra revealed that more Zn atoms in ZnFe2O4 of M-1200 occupied tetrahedral sites than M-900, resulting in a sharper A1g mode (∼647 cm−1), more ordered spinel structure and less antisite defects. Compared with visible-light responsive sphalerite (Zn, Fe)S, M-1200 performed more 200 nm of red-shifted optical absorption, 2.5 times at most higher the incident photon-to-electron conversion efficiency (IPCE) and 2–3-fold photocatalytic efficiency towards degradation of methyl orange and inactivation of Escherichia coli K-12. Besides, the photocatalytic activities of M-1200 preponderate over M-900, typical visible-light catalyst ZnFe2O4 and ZnO/ZnFe2O4 mechanically mixed sample. The optimization of lattice structure and the establishment of special band alignment were suggested to be remarkably beneficial to the separation of photogenerated electrons-holes and promote the photocatalytic performance. This study would enlighten a feasible and efficient strategy to fabricate coupled photocatalyst by utilizing Earth-abundant and low-cost natural minerals for solving environmental problems.

Excitonic Properties of Chemically Synthesized 2D Organic-Inorganic Hybrid Perovskite Nanosheets.

Abstract: 2D organic-inorganic hybrid perovskites (OIHPs) represent a unique class of materials with a natural quantum-well structure and quasi-2D electronic properties. Here, a versatile direct solution-based synthesis of mono- and few-layer OIHP nanosheets and a systematic study of their electronic structure as a function of the number of monolayers by photoluminescence and absorption spectroscopy are reported. The monolayers of various OIHPs are found to exhibit high electronic quality as evidenced by high quantum yield and negligible Stokes shift. It is shown that the ground exciton peak blueshifts by ≈40 meV when the layer thickness reduces from bulk to monolayer. It is also shown that the exciton binding energy remains effectively unchanged for (C6 H5 (CH2 )2 NH3 )2 PbI4 with the number of layers. Similar trends are observed for (C4 H9 NH3 )2 PbI4 in contrast to the previous report. Further, the photoluminescence lifetime is found to decrease with the number of monolayers, indicating the dominant role of surface trap states in nonradiative recombination of the electron-hole pairs.

Simple Synthesis of Large Graphene Oxide Sheets via Electrochemical Method Coupled with Oxidation Process.

Abstract: In this paper, we report a simple two-step approach for the synthesis of large graphene oxide (GO) sheets with lateral dimensions of ≈10 μm or greater. The first step is a pretreatment step involving electrochemical exfoliation of graphite electrode to produce graphene in a mixture of H2SO4 and H3PO4. The second step is the oxidation step, where oxidation of exfoliated graphene sheets was performed using KMnO4 as the oxidizing agent. The oxidation was carried out for different times ranging from 1 to 12 h at ∼60 °C. Prepared GO batches were characterized using a number of spectroscopy and microscopy techniques such as X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), and UV–visible spectroscopy. Raman and thermogravimetric analysis techniques were used to study the degree of oxidation in the as-synthesized GO batches. The UV–visible absorption spectrum showed an intense peak at 230 nm and a...

Synthesis and Optical Properties of Colloidal M3Bi2I9 (M = Cs, Rb) Perovskite Nanocrystals

Abstract: Bulk Cs3Bi2I9 exhibits zero-dimensional (0-D) perovskite crystal structure at the molecular level, providing scopes for novel optical properties compared to three-dimensional perovskite structures. Here, 0-D refers to the crystal structure irrespective of the size of the crystal. We have prepared colloidal Cs3Bi2I9 nanocrystals and elucidated the unique optical properties arising from their 0-D crystal structure. Absorption spectrum at 10 K confirms that the electronic band gap of Cs3Bi2I9 nanocrystals is at 2.86 eV, along with a sharp excitonic peak at 2.56 eV, resulting in a very high excitonic binding energy, EbX = 300 meV. Interestingly, we observe two peaks in the photoluminescence spectra at room temperature on both sides of the excitonic absorption energy. Because EbX (300 meV) ≫ effective phonon energy (36 meV), the phonon-mediated relaxation of carriers from conduction band minimum to the excitonic state is suppressed to an extent. Consequently, two photoluminescence peaks related to both the bul...

Solution-processed yolk–shell-shaped WO3/BiVO4 heterojunction photoelectrodes for efficient solar water splitting

Abstract: The WO3/BiVO4 heterojunction is regarded as one of the most promising photoanode materials for photoelectrochemical (PEC) water splitting. To improve the solar water splitting efficiency, maximizing the solar light absorption efficiency in a photoelectrode is still a critical issue. Here, to achieve the aforementioned need, we designed and fabricated a WO3 film consisting of yolk–shell structured nanoparticles via solution processing. A thin BiVO4 layer with a smaller bandgap was coated onto the surface and inside the WO3 shells, providing a rationally designed inner space between the particles and the shell for better electrolyte accessibility. The yolk–shell-shaped PEC photoanode not only induces efficient light absorption but also plays an important role in electron collection from BiVO4 due to an enlarged contact area. The structure–PEC performance relationship was studied by combining ultraviolet-visible (UV-vis) absorption spectroscopy with a specular and diffuse reflectance technique, which illustrates that the yolk–shell morphology has a superior light absorption ability than conventional hollow or dense film structures. The pure yolk–shell (Y-WO3/BiVO4) photoanode possessed a photocurrent density of 2.3 mA cm−2 and achieved a highest value of ∼5.0 mA cm−2 after adding a Fe–Ni co-catalyst at a bias of 1.23 V vs. RHE under AM 1.5 illumination (100 mW cm−2).

FTIR, electronic polarizability and shielding parameters of B 2 O 3 glasses doped with SnO 2

Abstract: In this work, six glass samples with nominal compositions (35Li2O–10ZnO–55B2O3) + (xSnO2: 0 ≤ x ≤ 3 wt%) have been prepared by solid state reaction method. Spectra of UV–visible absorption for these glasses have been performed in wavelength within the range 200–1100 nm. FTIR has been recorded in the range of 4000–400 cm−1 to estimate the vibrational modes in the samples. The direct and indirect optical energy band gap ( $$E_{{\text{g}}}^{{{\text{ASF}}}}$$ ) and the corresponding refractive index (n) have been calculated by absorption spectrum fitting model. Molar refraction (Rm), polarizability (αm), reflection loss (RL), and optical transmission (T) for the glass samples have been evaluated. Moreover, the mass attenuation coefficients (µ/ρ) have been evaluated using the Monte Carlo code (MCNPX, version 2.6.0) in the energy range 0.356–1.33 MeV to understand the radiation shielding properties for the prepared glasses. From the µ/ρ values, we have calculated some other parameters such as effective atomic number (Zeff), the half value layer, and the mean free path for the present glass samples. The results revealed that the investigated glass samples are promising for the laser stimulated nonlinear optics and the composition with the highest value of SnO2 content (3.0 wt%) is encouraging candidate for nuclear radiation shielding.

Effect of PbO on Optical Properties of Tellurite Glass

Abstract: Binary (1 − x)(TeO2) − x(PbO), x = 0, 0.10, 0.15, 0.20, 0.25, 0.30 mol% glass system was fabricated using melt quenching method. X-ray diffraction (XRD) technique was employed to confirm the amorphous nature. The microanalysis of the major components was performed using energy dispersive EDX and X-ray spectrometry. Both the molar volume and the density were measured. FTIR and UV spectra were recorded at 400–4000 cm–1 and 220–800 nm, respectively. The optical band gap (Eopt), Urbach’s energy (Eu), index of refraction (n) were calculated using absorption spectrum fitting (ASF) and derivation of absorption spectrum fitting (DASF) methods. Molar refraction Rm and molecular polarizability α m have been calculated according to (ASF) method.

Simplified molecular absorption loss model for 275–400 gigahertz frequency band

Abstract: This paper focuses on giving a simplified molecular absorption loss model for a 275–400 GHz frequency band, which has significant potential for variety of future short and medium range communications. The band offers large theoretical data rates with reasonable path loss to theoretically allow even up to kilometer long link distances when sufficiently high gain antennas are used. The molecular absorption loss in the band requires a large number of parameters from spectroscopic databases, and, thus, the exact modeling of its propagation characteristics is demanding. In this paper, we provide a simple, yet accurate absorption model, which can be utilized to predict the absorption loss at the above frequency band. The model is valid at a regular atmospheric pressure, it depends on the distance, the relative humidity, and the frequency. The existing simplified model by ITU does not cover frequencies above 350 GHz and has more complexity than our proposed model. The molecular absorption loss increases exponentially with the distance, decreasing the utilizable bandwidth in the vicinity of the absorption lines. We provide a model to approximate the window widths at the above frequency band. This model depends on the distance, the relative humidity, the frequency, and the maximum tolerable loss. It is shown to be very accurate below one kilometer link distances.

Hydrothermal synthesis of MoS2 nanosheets for multiple wavelength optical sensing applications

Abstract: In the present work, MoS2 nanosheets were synthesized by a hydrothermal method for optical sensing application. X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Raman and UV–vis spectroscopy were carried out to characterize the synthesized MoS2 nanosheets. SEM and TEM images showed the morphology of ultrathin nanosheets of MoS2. Optical sensor of MoS2 nanosheets was fabricated and thoroughly studied using various laser excitation wavelengths (λex): 440 nm (indigo); 460 nm (blue); 550 nm (green); 570 nm (yellow); 635 nm (red) and 785 nm (infra-red). The excellent photoresponsivity was observed in the visible range and maximum was found to be 23.8 μA/W for λex: 635 nm (red illumination). The mechanism for photoresponse was proposed and correlated with the absorption spectroscopy. The response and recovery times for 635 nm were 2.5 and 3.2 s, respectively. The photoresponsive characteristics of MoS2 nanosheets were also explored as a function of optical power density.

Identification of Stabilizing High-Valent Active Sites by Operando High-Energy Resolution Fluorescence-Detected X-ray Absorption Spectroscopy for High-Efficiency Water Oxidation

Abstract: Composite electrocatalysts have exhibited high activities toward water electrolysis, but the catalytically active sites really in charge of the reaction are still debatable while the conventional in situ X-ray spectroscopies are not capable of conclusively identifying the interaction of these materials with the electrolyte because of the complexity of catalysis. In this work, by utilization of operando Kβ1,3 high-energy resolution fluorescence-detected X-ray absorption spectroscopy (HERFD-XAS) with a small incident angle, the operando quadrupole transition obviously showed that oxygen directly interacted with 3d orbitals of Co ions rather than that of Fe ions. Most importantly, Fe ions can promote the stabilization of the Co ions under a higher valent state during water oxidation, which may lead to a stable intermediate of reactant and its superior intrinsic activity. Accompanied by the first-principle calculations, the intermediates between 3d orbitals for surface Co ions and O 2p orbitals for the attach...