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In this study, Ni-Fe alloy nanoparticles were prepared using the proteic sol–gel method, followed by a reduction in H2 at 500 and 700 °C, namely hereafter as NiFe-500 and NiFe-700, respectively. The morphological, structural, and magnetic properties were tuned via the thermal treatment in H2. The samples were studied using XPS, TEM, Mössbauer spectroscopy, DC magnetic measurements, and electrochemical measurements. Ritveld refinements showed that the sample NiFe-500 has FCC (face-centered cubic) and BCC (body-centered cubic) NiFe alloys, while the sample NiFe-700 has only FCC NiFe alloy. For both samples, magnetization measurements in the range of 300–900 K showed the presence of the Griffiths phase, indicating the formation of clusters of either Fe or Ni-Fe alloys rich in Fe. The sample NiFe-500 presented ferromagnetic (FM) transitions at 533, 700, and 834 K, assigned to the alloys Ni37Fe63-FCC, Ni46Fe54-FCC, and Ni55Fe45-FCC, respectively. In contrast, we could not observe the FM transition of the BCC Ni-Fe alloy because of limitations in our experimental setup (T ≤ 900 K). Meanwhile, three FM transitions were observed for the sample NiFe-700 at 480, 655, and 825 K, attributed to the alloys Ni34Fe66-FCC, Ni43Fe57-FCC, and Ni54Fe46-FCC, respectively. At 5 K, the samples NiFe-500 and NiFe-700 have saturation magnetizations of 164.2 and 173.6 emu g−1, respectively. For application in Oxygen Evolution Reaction catalysis, the samples NiFe-500 and NiFe-700 showed different overpotentials of 319 and 307 mV at 10 mA cm−2. These low overpotential values indicate a higher electrochemical activity of the FCC Ni-Fe alloy and, for both samples, a superior electrocatalytic activity in comparison to RuO2 e IrO2 conventional catalysts. Furthermore, the samples showed high electrochemical stability in chrono potentiometric studies for up to 15 h. This current work highlights that the Ni-Fe alloys produced via the proteic sol–gel and with a reduction in H2 methods can be promising for OER systems due to their good performance and low costs. [ABSTRACT FROM AUTHOR]

• Comments on the research article in Materials Letters 275 (2020) 128094. • Discussion on the overpotential reported of 36 and 68 mV vs. RHE for J = 20 mA cm−2 toward OER. • Experimental and scientific content is not accurate for the discussion of Tafel and ECSA. This is a comment on the paper Materials Letters 275 (2020) 128,094 (DOI: https://doi.org//10.1016/j.matlet.2020.128094) titled "A facile two-step synthesis of Ag/CuCo 2 O 4 supported on nickel foam as a high-performance electrocatalyst for oxygen evolution reaction". Herein, we conducted a critical assessment on interpretation of the experimental results, revealing that the reported overpotentials of only 36 and 68 mV vs. RHE for a current density of 20 mA cm−2 toward OER are mistaken. [ABSTRACT FROM AUTHOR]

In this work, we report copper oxide nanofibers (CuO – N) synthesized by Solution Blow Spinning (SBS) for oxygen evolution reaction (OER), and their comparison with a control sample based on a commercial powder (CuO – C). Both materials were characterized by various techniques, including X-ray diffraction (XRD), magnetometry, scanning electron microscopy (SEM), and spectroscopy (Fourier transform infrared (FT-IR), Raman and X-ray photoelectron (XPS)) to determine the purity, microstructural and surface chemical properties. Subsequently, the performance of copper oxide catalysts in a 1.0 M KOH solution was investigated. Copper oxide with nanofiber morphology (CuO – N) exhibited a small overpotential of 385 mV @ 10 mA cm−2 and a Tafel coefficient of only 76 mV dec−1, i.e., fast kinetics for water splitting, a result that is modulated by oxygen vacancies (O 2 /O 1 = 0.83). The oxygen vacancies are due to the presence of Cu1+ in the lattice. The analyses of the magnetization measurements at 5 K suggest a larger amount of Cu1+ in sample CuO – N. Therefore, this work sheds light on how to design low-cost nanofibrous catalysts based on abundant transition metals in the earth's crust by SBS, an economical and scalable technique, which is promising for energy applications. [Display omitted] [ABSTRACT FROM AUTHOR]

The development of highly efficient catalysts for oxygen (OER) and hydrogen (HER) evolution reactions are fundamental for the generation of new sources of energy. To meet the global demand of energy, non-noble metal catalysts based on transition metals, in particular, Nickel (Ni) and Copper (Cu) metals are being widely explored and studied as promising candidates for electrocatalysts. Therefore, here we present: (a) the Sol-gel synthesis that uses chitosan as a polymerizing agent and subsequent reduction in H 2 gas to synthesize carbon-coated NiCu nanoparticles, and (b) the microstructural and electrochemical evaluation of Ni 95 Cu 5 -C and Ni 85 Cu 15 -C samples. X-ray diffraction confirms the NiCu phase, while Raman spectroscopy confirms the presence of carbon. Field emission scanning electron microscopy shows nanoparticles with spherical morphology. From the electrochemical point of view, it was observed that the increase in copper content impairs the activity for oxygen evolution reaction when evaluated in 1.0 M KOH electrolyte. The Ni 95 Cu 5 -C electrocatalyst exhibited higher activity than Ni 85 Cu 15 -C, confirmed by its low overpotential value (η = 319 mV vs. RHE) and Tafel slope (73 mV dec−1), and high values of C DL (4.1 mF cm−2), ECSA (102.5 cm2), SA (2.19 mA cm−2) and TOF (1.87 x10−4 mol O 2 s−1). This work highlights a simple and inexpensive method to obtain Nickel-Copper-Carbon catalysts for application in water splitting in alkaline media. [Display omitted] • Nickel-Copper-Carbon was prepared by sol-gel methodology with subsequent reduction in H 2. • Commercial chitosan biopolymer was used as polymerizing agent. • Electrochemical performance of samples is highly dependent on Nickel content. • Ni 95 Cu 5 -C showed excellent OER performance, with an overpotential of 319 mV vs. RHE at J = 10 mA cm−2. [ABSTRACT FROM AUTHOR]

Among the most critical components for water-derived hydrogen fuel, the study of electrocatalysts as anode for the oxygen evolution reaction (OER) is an important topic in the water splitting process. In this work, the CuCo 2 O 4 –CuO composite electrode is synthesized directly on nickel foam to evaluate its potential as OER catalyst in an alkaline medium. An interesting strategy is to use flaxseed oil as a polymerizing agent in a sol-gel process combined with hydrothermal. A low overpotential value of 289 mV vs RHE at 10 mA cm−2 current density and a Tafel slope of 71 mV dec−1 were observed, which represents an electrocatalytic performance superior to other Cu and Co based oxides in the literature. Short-term stability testing of 15 h demonstrates stable overpotential with no observable secondary phase after measurements. The successful outcome of this work is a result of the promising green chemical approach herein used to obtain electrocatalysts grown directly on conductive substrates for water oxidation. [Display omitted] • Green synthesis of CuCo 2 O 4 –CuO on nickel foam substrate. • Flaxseed oil (Linum usitatissimum) was used as a polymerizing agent. • Two-step synthesis combining proteic sol-gel and hydrothermal routes. • CuCo 2 O 4 –CuO/Ni foam with overpotential of 289 mV vs RHE at J = 10 mA cm−2. [ABSTRACT FROM AUTHOR]

[Display omitted] • Medium/high-entropy oxides with Rock Salt structure were made via Air-Heated Solution Blow Spinning (A-HSBS). • Replacing Cu with Co ions shifts the Néel temperature (TN) to higher temperatures. • Co addition increased Ni³⁺/Ni²⁺ states, raising the band gap from 1.42 to 2.47 eV. • (Ni 0.2 Mg 0.2 Zn 0.2 Co 0.4)O nanofibers showed 326 mV overpotential @10 mA cm−2 for OER in alkaline media. In this study, we investigated the fabrication of high entropy rock salt (Ni 0.2 Mg 0.2 Zn 0.2 Cu 0.2-x Co 0.2+x) (x = 0, 0.1, 0.2) nanofibers via air-heated solution blow spinning (A-HSBS). The samples were monophasic, with compositions considering the gradual substitution of non-magnetic Cu by magnetic Co, transitioning samples from high to medium configurational disorder entropy. SEM images revealed that nanofibers were composed of aggregated nanoparticles. XRD showed a gradual reduction in the lattice parameter due to the replacement of Cu by Co. UV–Vis analysis indicated an increase in the band gap from 1.42 to 2.47 eV with increasing Co concentration. Magnetically, the addition of Co caused a positive shift in the Néel transition temperature (T N), increasing from 117 K to 155 K. The oxides exhibited antiferromagnetic behavior (AFM) below T N and displayed a spin glass regime. XPS analysis showed an increase in the charge state of Ni3+ and the presence of Co3+ with the substitution of Cu by Co. The electrocatalytic activity for the oxygen evolution reaction was enhanced in the medium-entropy oxide catalysts (x = 0.2), achieving an overpotential of 326 mV@10 mA cm−2, along with excellent short-term stability for 12 h. [ABSTRACT FROM AUTHOR]

In this work, we report a novel synthesis route of α-Mn 2 O 3 porous fibers obtained by air-heated solution blow spinning (A-HSBS) and their application as an electrocatalyst for the oxygen evolution reaction (OER). Our α-Mn 2 O 3 porous fibers presented superior OER performance to other electrocatalysts reported in the literature, and it is because the fibrous morphology and multiple Mn charge states, which lead to a small overpotential of 378 mV @ 10 mA cm−2. Furthermore, the fibrous α-Mn 2 O 3 electrode exhibited long-term electrochemical stability confirmed by chronopotentiometry testing for 18 h at a current density of 10 mA cm−2 and showing retention/preservation of microstructural properties. Our results underscore the potential of the A-HSBS for producing electrodes with a fiber-like morphology, based on transition metals. The proposed synthesis route can provide economical, durable, and efficient electrocatalysts for water splitting, which can be applied in several applications, such as electrocatalysts, biosensors, among others. • α-Mn 2 O 3 porous fibers were synthesized by the A-HSBS technique. • Efficient OER performance and high electrochemical stability of α-Mn 2 O 3 porous fibers. • The sample exhibits an overpotential of 378 mV vs. RHE @ 10 mA cm−2 and a Tafel slope of just 67 mV dec−1. • The excellent performance of α-Mn 2 O 3 fibers is because of its surface porosity. [ABSTRACT FROM AUTHOR]

The electrolysis of alkaline solutions is one of the most used strategies for producing hydrogen (H 2). This process distinguishes itself by breaking the water molecule (water splitting) through two semi-reactions: Hydrogen Evolution Reaction (HER, cathodic reaction) and Oxygen Evolution Reaction (OER, anodic reaction). The OER is fundamental for several electrochemical technologies related to generate and store energy. New research for developing low-cost electrocatalysts with a good electrochemical activity using more earth-abundant elements has intensified in recent years. The current work aims to study the effect of Fe doping on the OER of calcium cobaltites, Ca 3 Co 4- x Fe x O 9 (x = 0, 0.1, 0.4, and 0.8). Powders were obtained by a proteic sol-gel method using gelatin with calcination at 900 °C for 2 h. The resultant samples were characterized by X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM). X-ray photoelectron spectroscopy (XPS) provided information on the surface chemical states, while Mössbauer spectroscopy indicated that Fe has a strong preference for octahedral sites in the CoO 2 layer rather than in the Ca 2 CoO 3 layer in the calcium cobaltite misfit-type structure. Linear sweep voltammetry (LSV), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) were used to analyze the electrochemical performance. The results indicate that Ca 3 Co 3·2 Fe 0·8 O 9 needs the lowest overpotential of 320 mV to generate a current density of 10 mA cm−2. [Display omitted] • Calcium cobaltites (C349) synthesized by a proteic sol-gel method. • Fe location in the calcium cobaltite structure through Mössbauer spectroscopy. • C349–Fe0.8 sample needed a potential of 320 mV to generate a current density of 10 mA cm−2. [ABSTRACT FROM AUTHOR]

Cobalt-based oxides are among the most promising electrocatalysts for oxygen evolution reactions (OER). In this context, this work reports the synthesis of manganese-doped cobaltites using the Zeolitic-Imidazolate Frameworks 67 (ZIF-67) as template. The incorporation of manganese ions into ZIF-67 structure was evaluated in ethanol and methanol, in order to obtain the best synthetic route. Non-doped (ZIF-67C) and Mn-doped cobaltites (Mn/ZIF-67C(E) and Mn/ZIF-67C(M)) were obtained after thermal treatment at 350 °C. Structural and morphological properties were investigated and presence of Mn3+ and Mn4+ was confirmed by X-ray photoelectron spectroscopy (XPS) data and magnetization curves. The electrocatalytic activity in OER was investigated in alkaline medium for manganese cobaltites, and compared to the ZIF-67C. Overpotentials to generate a current of 10 mA cm−2 were 338 mV and 356 mV for Mn/ZIF-67C(E) and Mn/ZIF-67C(M), respectively. These results are superior to those found for similar materials in the literature. The material obtained in methanol (Mn/ZIF-67C(M)) presents lower overpotential, however, shows superior electrocatalytic performance for current density above 100 mA cm−2, therefore being an efficient electrode for commercial electrolysers. [ABSTRACT FROM AUTHOR]

The development of electrocatalysts for water splitting is a challenging issue for researchers in the field, because the oxygen evolution reaction (OER) occurs in multiple stages and with slow kinetics. In this study, Tungsten (W) and Molybdenum (Mo) (refractory metals) particles with a Body-Centered Cubic (BCC) structure were obtained through the high-energy milling of precursors Ammonium paratungstate (APT) and Ammonium heptamolybdate (AHM)) followed by reduction/decomposition in hydrogen (H 2) atmosphere. It was found that particle size and oxygen vacancies strongly influence the catalytic activity of refractory metals. In fact, the W smaller particle/crystallite size, confirmed by Scanning Electron Microscope (SEM) and X-ray diffraction (XRD) techniques, as well as the larger ratio O 2 /O 1 = 0.81 determined by X-ray photoelectron spectroscopy (XPS), leads to a sharp increase in current density compared to Mo that have O 2 /O 1 = 0.75. The W particles only require 322 mV vs. RHE to generate a current density of 10 mA cm−2, against 334 mV vs. RHE for Mo. The W showed superior electrocatalytic performance, with low overpotential, Tafel slope of 53 mV dec−1, C DL of 1.79 mF cm−2, ECSA of 44.75 cm2, the specific activity of 10.72 mA cm−2, and mass activity of 2400 A g−1. Therefore, this two-step synthesis method is highly effective in producing catalysts with excellent electrochemical responses for energy applications. New catalysts based on refractory metallic materials for oxygen evolution reaction were developed by high energy milling. Electrochemical measurements carried out in an alkaline medium show that tungsten and molybdenum have overpotentials of 322 and 334 mV vs. RHE. [Display omitted] • Refractory metals were prepared by a simple and highly scalable two-step methodology. • Tungsten and Molybdenum particles were explored as a new catalyst in the alkaline medium for Oxygen Evolution Reaction. • Electrochemical performance is highly dependent on particle/crystallite size and oxygen vacancies. • Tungsten particles showed excellent performance, with an overpotential of only 322 mV vs. RHE at J = 10 mA cm−2. [ABSTRACT FROM AUTHOR]

The development of effective and low-cost catalysts for the oxygen evolution reaction (OER) has become an effective and promising strategy for sustainable energy technologies. In this work, we report a synthesis route for preparing MnCo 2 O 4 nanoparticles on nickel foam (Ni foam) through a facile sol-gel method using Flaxseed (Linum usitatissimum) as a polymerizing agent and subsequent an adapted hydrothermal process. Here, a large surface area was obtained due to the small particle size combined with the absence of binders to promote the adhesion of the active material on the substrate. Thus, this seems to be an interesting strategy to boost electrocatalytic reactions. The structural, microstructural, and surface properties of MnCo 2 O 4 electrodes are investigated by XRD, FESEM, TEM, FTIR, Raman, and XPS analysis. This electrode exhibits an overpotential of 296 mV (at 25 mA cm−2 current density), a Tafel slope of 82 mV dec−1, and excellent electrochemical stability for 15 h. This approach combines the features of a green synthesis with an adapted hydrothermal route to offer the advantages of a controllable reaction process, with good reproducibility, ally to uniform particle size distribution, short reaction time, and, mainly, respect for the environment. This demonstrates great potential in reproducing effective OER electrocatalysts for future applications. [Display omitted] • Green synthesis of MnCo2O4 using sol-gel method and coupling this to an adapted hydrothermal directly onto the nickel foam to obtain a self-supported electrode. • Biological substrates replace traditional chemical solutions and stabilization agents. • Flaxseed (Linum usitatissimum) was used as the reducing agent. • The self-supported electrode (MnCo2O4-G) showed an overpotential of 296 mV (@ 25 mA cm-2), with the ECSA value of 2750 cm². [ABSTRACT FROM AUTHOR]

This work studies the magnetic behavior of a CoFe 2 /CoFe 2 O 4 composite and a CoFe 2 alloy obtained by proteic sol-gel synthesis as electrocatalysts for the oxygen evolution reaction (OER). Both samples were obtained through a two-step synthesis: (i) firstly, the preparation of CoFe 2 O 4 nanoparticles using the protein sol-gel synthesis route and (ii) secondly, the reduction reaction of cobalt ferrite nanoparticles at 300 °C (CoFe 2 /CoFe 2 O 4) and 500 °C (CoFe 2) using H 2 atmosphere. The morphological, structural, and magnetic properties were investigated by scanning and transmission electron microscopy (FESEM and TEM), X-ray diffraction (XRD), Mossbauer spectroscopy (MS) and magnetometry as a function of field and temperature. The FESEM and TEM analyses revealed that the nanoparticles have a sphere-like morphology. The nanostructured character of the samples was demonstrated through the Rietveld refinement of the XRD data. The Mössbauer spectra revealed the formation of the metallic phase of CoFe 2 in the reduced samples. Magnetization versus field (M-H) curves obtained at 5 K reveal that CoFe 2 /CoFe 2 O 4 and CoFe 2 samples show saturation magnetizations (Ms) of 196 and 226 emu g−1, respectively. For OER applications, the CoFe 2 /CoFe 2 O 4 and CoFe 2 samples showed overpotentials of 304 and 291 mV vs RHE for 10 mA cm−2. Furthermore, the samples showed high electrochemical stability in chronopotentiometry studies for up to 15 h. These results suggest that materials based on transition metals, Co and Fe, are promising in developing electrodes for energy storage and conversion systems, due to their high performance and low manufacturing cost. [Display omitted] • Cobalt-iron based compounds by a proteic sol-gel synthesis route. • Magnetic measurements as a function of magnetic field and temperature. • High magnetic moment and improved OER performance for the CoFe 2 alloy. • CoFe 2 delivers an ultralow overpotential of 380 mV at 450 mA cm−2 for OER. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesis of NiFe 2 O 4 nanoparticles using EDTA-Citrate method. • Morphology of triangular-shaped aggregates that change with temperature. • NFO400 shows an overpotential of 326 mV vs RHE at J = 10 mA cm−2. Nickel ferrite nanoparticles, NiFe 2 O 4 , were prepared using the EDTA-Citrate complexation method. A systematic study was carried out on the microstructural, morphology, magnetic, vibrational and electrochemical properties of the samples. According to Rietveld refinements, all samples are single-phase with spinel cubic structure with sizes ranging from 15 to 93 nm. Electron microscopy analyzes revealed the formation of aggregates made of several nanocrystals. The aggregates have triangular shape that changes in size as a function of the calcination temperature. The magnetic hysteresis curves at 300 K are typical of ferrimagnetic materials and showed increasing values of magnetic parameters with the size of the crystallites. The results demonstrated a significant NiFe 2 O 4 catalytic activity towards oxygen evolution reaction (OER) in an alkaline medium with overpotential of 326 mV vs. RHE at J = 10 mA cm−2 for the particles obtained at 400 °C (NFO400), and high electrochemical stability over 15 h under an electrolysis current of J = 10 mA cm−2. LSV, Tafel, SA, J m , TOF and EIS analysis revealed that decreasing particle size favors kinetics through a more efficient process of mass and charge transfer. [ABSTRACT FROM AUTHOR]

[Display omitted] • Green synthesis of Co 3 O 4 nanoparticles. • Psyllium husk (Plantago Ovata) is used as a polymerizing agent. • Co 3 O 4 -400 °C shows an overpotential of 328 mV vs RHE at J = 10 mA cm−2. The continuous supply of hydrogen from renewable sources through water electrolysis technology is a key issue for the development of humanity. To meet this purpose, catalysts based on transition metals (Ni, Fe and Co) are promising candidates for the hydrogen and oxygen evolution reactions. Therefore, in this work, nanocrystalline Co 3 O 4 with a spinel-like cubic structure was prepared by a proteic sol–gel synthesis using psyllium husk as a polymerizing agent, and later tested as an electrocatalyst for the oxygen evolution reaction (OER). The purity of the Co 3 O 4 phase was confirmed by several characterization techniques, including X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy and X-ray Photoelectron Spectroscopy (XPS). The size of crystallites and particles obtained from Rietveld refinement of X-ray diffraction patterns ranged from 16.5 nm to 25.3 nm for powders calcinated at 400 °C and 600 °C, respectively, confirming nanometric Co 3 O 4 powders. Scanning electron microscopy shows nanostructures with predominantly spherical morphology. From the electrocatalytic point of view, it was observed that the larger particle size impairs the oxygen evolution reaction. The Co 3 O 4 calcined at 400 °C showed superior electrocatalytic performance, with an overpotential of 328 mV at 10 mA cm−2, Tafel slope of 71 mV dec-1, C DL of 5.46 mF cm−2, ECSA of 91 cm2, specific activity of 4.73 mA cm−2 and mass activity of 718 A g−1. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fe-based spinels using commercial flavorless gelatin as a chelating agent. • Spinel ferrites with electrocatalytic performance toward oxygen evolution reaction. • Copper-oxygenated groups boost the electrocatalytic performance of CuFe 2 O 4. In this work, spinels of MFe 2 O 4 (M = {Ni, Co, Cu}) were successfully prepared by proteic sol-gel method using commercial flavorless gelatin as a chelating agent. To break down aggregated particles, the samples were milled in alcohol at 400 rpm for 1 h. According to Rietveld refinements and transmission electron microscopy, the samples had crystallite and particle sizes in the range of 36–53 nm and 44–147 nm, respectively, confirming the as-prepared samples in a nanoscale. X-ray diffraction and Rietveld refinement confirmed that the samples are single phase. In addition, Mössbauer spectroscopy analysis and X-ray photoelectron spectroscopy revealed the mixed spinel composition. Besides, X-ray photoelectron spectroscopy showed surface oxygen vacancies, given by ratio areas between oxygen vacancies (O V) and oxygen in the lattice (O L), of 0.63, 0.27 and 0.10 for NiFe 2 O 4 , CuFe 2 O 4 and CoFe 2 O 4 powders, respectively. Magnetic measurements showed ferrimagnetic behavior for all samples. Toward oxygen evolution reaction (OER), copper-oxygenated groups on the CuFe 2 O 4 nanoparticle surface may play an important role, once CuFe 2 O 4 showed superior electrocatalytic performance, with overpotentials of 369 mV (CuFe 2 O 4) < 386 mV (NiFe 2 O 4) < 448 mV (CoFe 2 O 4) at a current density of 10 mA cm−2 and Tafel slopes of 76.3 mV dec-1 (CuFe 2 O 4), 85.7 mV dec-1 (NiFe 2 O 4) and 148.1 mV dec-1 (CoFe 2 O 4). All samples exhibited mechanical stability during the OER process. [ABSTRACT FROM AUTHOR]

[Display omitted] • Preparation of Cu-doped calcium cobaltite by proteic sol–gel method. • Cu doping decreases the surface area available for OER. • Mechanical and chemical stability is not affected by Cu doping. Herein, the effect of Cu-doping on the OER activity of misfit calcium cobaltites (Ca 3 Co 4-x Cu x O 9+δ ; x = 0, 0.05, 0.10, and 0.15) was evaluated under an alkaline medium. Powders obtained by a proteic sol–gel method were systematically studied using a variety of characterization techniques. Rietveld refinement from XRD data revealed that there was no change in the crystalline structure of the doped cobaltites. Electrochemical analyses showed that the performance of the catalysts decreases with increasing the amount of Cu. Electrochemical impedance spectroscopy revealed that the polarization resistance (R P) increases with the degree of doping, harming the kinetics of faradaic processes in OER. [ABSTRACT FROM AUTHOR]