Electrochemical water splitting (EWS) into hydrogen and oxygen is essential for clean energy and a sustainable future. However, the most significant obstacle is the several anode oxygen evolution reaction (OER) processes, which limit practical applications. Nanofibers are one-dimensional materials with a large surface area, making them ideal to produce electrodes. By adjusting their secondary morphology (porosity, roughness, or grooves), their catalytic properties can be improved. This work emphasizes the production of porous ceramic fibers by solution blow spinning (SBS) method in conjunction with a cryogenic bath and phase separation by freezedrying. Co3O4 Cryo-SBS nanofibers enhance the OER properties by altering their surface morphology, creating more porosity for better access to active sites and improved surface reactivity. The significant performance of the cryogenic nanofibers required an overpotentials of ti10 = 320 mV in solution 1M KOH, whereas SBS-produced nanofibers typically require 353 mV for the same current density. At high current densities, Cryo-SBS nanofibers showed good performance for OER at an industrial scale. The overpotential values are like those of many metal oxides/hydroxides and reference materials like commercial IrO2 and RuO2. The results show that the modification of the nanofibers surface by freezing was effective in increasing the OER activity.

This work reports the development of efficient oxygen evolution reaction (OER) catalysts based on defect-engineered TiNb2O7 for alkaline water electrolysis. Herein, titanium niobate (TiNb2O7) was synthesized via a coprecipitation route followed by calcination at 950 degrees C under distinct isothermal dwell times (2 h, 4 h, and 6 h) to elucidate the effect of structural and morphological modifications on catalytic performance. X-ray diffraction confirmed the stabilization of the orthorhombic phase, while FE-SEM revealed particle growth from 135 nm (2 h) to 175 nm (6 h), consistent with coarsening driven by extended thermal treatment. Raman and FTIR analyses corroborated these results, confirming the preservation of crystalline integrity and providing evidence of the chemical bonding environment characteristic of Ti-O and Nb-O linkages. XPS and EPR analysis further highlighted a higher proportion of Ti4+/Ti3+ and Nb5+/Nb4+ species and an elevated Oads/Olat ratio in the 2 h sample, indicative of abundant oxygen vacancies. Electrochemical tests in 1 M KOH showed that the 2 h sample delivered the best performance, requiring only 287 mV to reach 10 mA cm-2 with a Tafel slope of 42 mV dec-1, outperforming the 4 h sample (301 mV, 50 mV dec-1) and the 6 h sample (348 mV, 67 mV dec-1). Electrochemical impedance spectroscopy confirmed superior charge-transfer kinetics for 2 h sample, with Rct decreasing from 1.60 Omega (1.50 V) to 0.28 Omega (1.70 V) and sub-millisecond relaxation times. Short-term durability under continuous alkaline electrolysis further evidenced operational stability over 23 h. These findings demonstrate that the electrocatalytic behavior of TiNb2O7 can be effectively enhanced through defect engineering, highlighting its potential for alkaline water electrolysis applications.

A future energy system where the supply of fuels, heat, and electricity is based exclusively on renewable energies relies heavily on technologies capable of converting fuels into electricity and vice versa (power-to-fuel or P2F) with high efficiency. In such a context, reversible solid oxide fuel/electrolysisElectrolysis cells (SOFCs/SOECs) are of urgent interest. The misfit calcium cobaltiteCalcium cobaltite electrode, [Ca2CoO3−δ]0.62[CoO2] (C349), has appeared as an attractive electrode material for solid oxide cell (SOC) applications due to offering a similar thermal expansion coefficient to that of classical electrolytes (e.g., doped ceria or stabilized zirconia), aligned with its good surface exchange kineticsSurface exchange kinetics. The current chapter provides a review of the understanding and optimization of C349-based electrodes, and within this perspective, the oxygen reaction mechanisms are extensively discussed. Different strategies to improve the electrochemical performance are also highlighted, such as doping, the addition of oxide ion conducting phases, interlayers between the electrode and electrolyte, processing methodologies, and the effect of electrode thickness. Its potential application in reversible SOCs in fuel cellFuel cell and electrolysis operation modes is presented and discussed. Finally, comparison with other Co-based electrodes is performed.

A multicationic spinel, (Co0.25Fe0.25Mn0.25Zn0.25)(3)O-4, is studied as an (electro)catalyst for the oxygen evolution reaction. It is compared with Co3O4, and the (electro)catalytic benefits of multiple cations in the spinel lattice are then demonstrated. A considerable increase in the lattice parameter of the multicationic oxide is observed through structural analysis, accompanied by increased local structural disorder. In addition, X-ray photoelectron spectroscopy reveals the presence of additional oxidation states, indicating a more complex electronic environment. The multicationic oxide exhibited, by linear sweep voltammetry, a reduction in overpotential of similar to 23 mV at 10 mA cm(-2) and of similar to 102 mV at 100 mA cm(-2). For the multicationic composition, the rate-determining step involves a chemical step subsequent to the first electron transfer step, as indicated by the Tafel slopes of similar to 54-65 mV dec(-1), while Co3O4 exhibits a higher Tafel slope of similar to 74-85 mV dec(-1), which indicates a slower electron transfer step for the Co3O4 sample. This change is in line with the different relaxation frequencies obtained by electrochemical impedance spectroscopy. According to chronoamperometry measurements, an overpotential of similar to 292 mV is obtained at 17 mA cm(-2) for the multicationic oxide, attributed to the cooperative electronic effects of active centers, which optimize the surface adsorption of intermediates.

The rock-salt fcc CoO is an important material in several technological applications. The synthesis of fcc CoO nanocrystals is a challenge, the major difficulty in preparing single phase CoO is due to the formation of hcp CoO, Co3O4 and the readily reducibility of Co2+ to zerovalent Co. In this work, we present a new method for synthesizing CoO nanocrystals and discuss their crystallinity, morphology, magnetic properties and discuss their application in the oxygen evolution reaction-OER process. The M-T zero-field cooling (zfc) and field cooling (fc) measurements under a field of 200 and 10 kOe showed a peak at 141 K that is related to the antiferromagnetic transition of fcc CoO. The zfc M-H measurement at 10 K showed a very weak hysteresis signal superimposed with a dominant linear behavior, typical of an antiferromagnetic phase. The CoO electrocatalyst in the OER experiments showed an overpotential of 278 mV at 10 mA cm-2, comparatively RuO2 and Ni foam had overpotentiais of 235 mV and 515 mV, both at 10 mA cm-2, respectively. It means that the 3 nm CoO nanoparticles have a similar electrocatalytic response as the expensive RuO2 material.

Ionic liquids (ILs) are widely utilized in various scientific fields and technologies, offering environmentally friendly alternatives to toxic volatile solvents. In particular, protic ionic liquids (PILs), a subset of ILs, boast advantages such as simple synthesis, low cost, and biodegradability. ILs are promising solvents for electrospinning, enabling the production of high-quality nanometric fibers. Despite their potential, challenges persist in electrospinning polymer solutions containing ILs or poly-(ionic liquid)-s, mainly due to changes in solution conductivity, leading to rheological alterations and jet instabilities. In contrast, Solution Blown Spinning (SBS) offers a solution to these challenges, employing a pressurized air system without electric fields and ensuring a high rate of fiber production. This study aims to produce polymeric submicrometric fibers by leveraging the benefits of ILs as additives, along with the practicality and adaptability of the SBS technique. Twelve compositions of poly-(vinyl alcohol) (PVA) and poly-(vinylpyrrolidone) (PVP) using 2-hydroxydiethylammonium propionate (2-HDEAPr) PIL were spun and characterized by SEM, FTIR, and DSC analyses. The addition of 0.25 mL of PIL was sufficient to reduce the average diameter compared to pure fiber, due to the plasticizing effect of the additive. The findings confirm the feasibility of fiber production by SBS, highlighting fiber smoothness, alignment, and continuity. The average fiber diameters measured were 0.55, 0.66, and 0.91 μm, respectively, for PVA-0.25 mL, PVA-0.50 mL, and PVA-1 mL PIL. Additionally, PVP compositions exhibited an average diameter of approximately 0.40 and 0.55 μm. Such results indicate the potential of these aqueous solution blow-spun fibers for the development of eco-friendly fibrous materials.

This work presents a simple and cost-effective approach for the one-step synthesis of MnCo2O4-reduced graphene oxide (MCO-rGO) for use as an anode material in the oxygen evolution reaction (OER). Here, both MCO and rGO are formed on a porous Ni foam through a wet chemical process, via oxidation of the spinel phase and the simultaneous thermal reduction of graphene oxide (GO) in an air atmosphere at 300 degrees C. The (electro)catalytic properties of the MCO-based electrodes are studied in an alkaline medium (1 M KOH) to evaluate the impact of rGO on various OER activity parameters, in controlled amounts of 10 wt% and 20 wt% GO. The composite with 20 wt% GO exhibits the lowest overpotential, 291 mV at 50 mA cm-2 (eta 50), which is 37 mV lower than the eta 50 value for the pure MCO. The Tafel slopes suggest that the MCO-based electrodes are governed by a competitive mechanism between the first electron transfer step and the chemical step following the first electron transfer, with the latter, involving chemical intermediates, being dominant. In agreement, electrochemical impedance spectroscopy (EIS) results recorded during the OER conditions show a decrease in the resistance associated with surface intermediates upon the addition of rGO. This improvement is attributed to the higher electrical conductivity of rGO and a potential increase in electrochemically active surface area. Furthermore, excellent electrochemical stability was achieved at a current density of 50 mA cm-2 for 20 h.

A double perovskite oxide with nominal composition YSr2Cu2FeO7+delta was successfully synthesized via the Pechini method and investigated as an electrocatalyst for the oxygen evolution reaction (OER). Structural, microstructural and chemical characterization was carried out using X-ray diffraction (XRD) with Rietveld refinement, scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM/EDS), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS), confirming the formation of the targeted phase, compositional homogeneity, and surface chemical states. The electrocatalytic performance of YSr2Cu2FeO7+delta for OER was evaluated and compared with that of commercial nickel foam (NF). The YSr2Cu2FeO7+delta electrode exhibited a low overpotential of 292 mV vs. RHE at 10 mA cm-2, outperforming NF, which required 345 mV vs. RHE under the same conditions. Stability tests demonstrated that YSr2Cu2FeO7+delta maintained stable operation for 24 h at 10 mA cm-2, indicating good electrochemical durability. Electrochemical impedance spectroscopy (EIS) analysis revealed improved charge-transfer characteristics for YSr2Cu2FeO7+delta, as reflected by lower charge-transfer resistance (RCT,GEO) than for NF. Post-electrochemical XRD, SEM and XPS analyses were performed to evaluate structural, chemical and microstructural stability, confirming the preservation of the material's structure after OER operation. These results highlight YSr2Cu2FeO7+delta as a promising non-noble-metal electrocatalyst with enhanced activity, charge-transfer kinetics, and operational stability.

This study reports the synthesis of CuO directly grown on nickel foam (NF) via a combined sol-gel and lowtemperature hydrothermal method. XRD, FESEM, FT-IR, and XPS analyses confirm the formation of crystalline CuO with well-defined morphology, structural integrity, and the presence of Cu2+ ions. Electrochemical tests in 1 M KOH show that the directly grown CuO (CuO-G) exhibits a larger electrochemically active area, lower charge transfer resistance, and improved oxygen evolution reaction (OER) activity compared to conventionally deposited CuO (CuO-D). CuO-G also shows lower overpotential, a smaller Tafel slope, and a higher turnover frequency (TOF), indicating enhanced catalytic efficiency. Long-term tests confirm the structural and morphological stability of the electrode. These results demonstrate that the direct growth strategy significantly enhances the electrochemical performance of CuO, making it a promising approach for energy conversion and storage applications.

This study presents an eco-friendly and efficient strategy for designing electrocatalysts for water electrolysis, particularly targeting the oxygen evolution reaction (OER). The electrocatalyst was developed from ligand-free cobalt oxide (Co3O4) nanoparticles grown directly on three-dimensional Nickel foam using a green sol-gel method followed by a closed low-temperature process and annealing. Uniquely, the synthesis used agar-agar (a natural polysaccharide from red algae) as a low-cost, biodegradable polymerizing agent. The resulting Co3O4/Ni foam electrodes showcased excellent structural integrity, with well-distributed nanoparticles forming a porous, sheet-like morphology. Compared to commercial Co3O4 catalysts, the grown electrodes displayed significantly better electrochemical performance - including a lower overpotential (eta 30 = 332 mV), a favorable Tafel slope (70 mV dec- 1), and greater electrochemically active surface area (ECSA). The improved kinetics were associated with increased in-situ growth, thus increasing the active surface area, and efficient charge transfer dynamics, confirmed by impedance spectroscopy. Importantly, the electrode maintained long-term stability over 15 h of continuous operation, making it a promising, sustainable candidate for noble-metal-free alkaline water splitting. This work paves the way for future development of eco-conscious and scalable electrocatalyst technologies.

In this work, carbon fibers were produced using the solution blow spinning (SBS) technique from polyacrylonitrile (PAN) blended with 0, 2.5, 5, and 10% of poly(vinylpyrrolidone) (PVP). Spun fibers were carbonized in a tubular oven and subsequently characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, carbon-nitrogen elemental analysis, and scanning electron microscopy (SEM) to observe their microstructural properties. Additionally, electrochemical tests, including potentiodynamic, potentiometric, and cyclic voltammetry, were conducted to evaluate the hydrogen evolution reaction (HER). Spectroscopic characterizations indicated that carbon fibers were produced by SBS. Moreover, it was possible to control the HER to suppress hydrogen evolution in lead-acid batteries.

Here, CoFe2O4 and NiFe2O4 spinel samples were synthesized using the ionic coordination reaction (ICR) method, and their structural, magnetic, and optical properties were systematically investigated for potential application as electrocatalysts for oxygen evolution reaction (OER). X-ray diffraction (XRD) analysis revealed average crystallite sizes of approximately 10.2 nm for CoFe2O4 and 21.3 nm for NiFe2O4. X-ray photoelectron spectroscopy (XPS) measurements indicated the presence of Co2+ species on the surface of CoFe2O4, while NiFe2O4 exhibited both Ni2+ and Ni3+ species, besides the Fe3+ ions. The coexistence of Ni2+ and Ni3+ is favorable for the formation of NiOOH, playing a crucial role in enhancing OER activity. The metal-oxygen bond lengths and bond angles were calculated and found to differ between the two spinel structures, which directly influence their magnetic behavior. CoFe2O4 and NiFe2O4 samples exhibited low overpotentials of 334 and 314 mV vs RHE at a current density of J = 10 mA cm-2, Tafel slope of 61 and 49 mV dec-1 and a turnover frequency (TOF) 2.5 x 10-3 mol O2 s-1. These findings demonstrate that the ICR-synthesized spinels possess excellent electrocatalytic performance for the oxygen evolution reaction.

The development of high‐performance electrocatalysts for oxygen evolution reaction (OER) is still a challenge to produce green hydrogen. Thus, herein, a new bifunctional metal–organic frameworks (MOF)‐derived CuCo 2 O 4 is obtained, applied as OER electrocatalyst and electrode for supercapacitors. All physicochemical and morphological characterization indicates the formation of a pure spinel structure CuCo 2 O 4 crystalline phase and coral reef‐like morphology. X‐ray photoelectron spectroscopy data showed major presence of Co 3+ and Cu + ions on the surface and high concentration of oxygen vacancies. OER electrocatalytic assays conducted in alkaline medium (1.0 M KOH) show a reduced overpotential ( η ) of 317 mV at 10 mA cm −2 and Tafel slope of only 49 mV dec −1 , besides excellent electrochemical stability up to 12 h. The material is also studied for supercapacitors applications via cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) analysis. CuCo 2 O 4 material presents specific capacity near 75 C g −1 , at least ≈2.8 times higher than pristine CuO and Co 3 O 4 at 1 A g −1 . This results indicate the MOFs‐derived CuCo 2 O 4 as a promising bifunctional material for energy conversion and storage.

The study investigated the impact of different preparation techniques (Mechanical Mixing - MM and High Energy Milling - HEM) and compaction pressures on the microstructure, sinterability and mechanical properties of the Cu-20 %WC composite using recycled WC. The results indicated that HEM promotes greater homogeneity, dispersion and refinement of the WC phase in copper, resulting in denser and more uniform microstructures after sintering. Although higher pressures increased the density of green compacts, they reduced densification during sintering, especially for powders prepared by MM, due to the segregation of the Cu and WC phases. On the other hand, compacts sintered with HEM powders prsented higher Vickers microhardness and better magnetic properties, attributed to the uniform distribution of WC particles and the increase in the interaction between the phases. Furthermore, the study highlights the influence of metallic impurities (Fe, Co and Ni) on the magnetic properties of the composite materials.

Electrolysis of water for hydrogen production is a promising approach to storing excess energy generated by renewable sources. The need for high-performance catalysts in water electrolysis has led to interest in fiber-like catalysts, which offer larger surface areas without the aggregation issues common to small nanoparticles. In this study, we report the synthesis of dual-phase CuO/CuNb2O6 nanofibers using the Solution Blow Spinning (SBS) technique and evaluate their performance in the oxygen evolution reaction (OER). The spun nanofibers consist of 23.17 wt% CuO and 76.83 wt% CuNb2O6 and exhibit excellent OER activity, with an overpotential of 380 mV at 10 mA cm- 2, a Tafel slope of 104 mV dec- 1, and outstanding short-term stability over 15 h. These findings suggest that the synthesized nanofibers are promising catalysts for OER in water electrolysis applications.

In this study, we investigated the fabrication of high entropy rock salt (Ni0.2Mg0.2Zn0.2Cu0.2-xCo0.2+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 Neel 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.

In this work, the high entropy oxide (HEO) (Fe0.2Ni0.2Co0.2Al0.2Zn0.2)3O4 was synthesized at 600 degrees C (labeled as HEO-600) by sol-gel method assisted with polyvinylpyrrolidone (PVP). Additional samples were produced at higher temperatures and the spinel and rock-salt high entropy oxides were formed. The characterizations were carried out by XRD, EDS, XPS, TEM, Mossbauer spectroscopy, AC and DC magnetometry, UV-vis, FTIR, and electrochemical experiments. For sample HEO-600, the XPS analysis confirmed the equimolar composition of the sample. The EDS results showed homogeneous distribution of the cations within the sample. The TEM showed non-aggregated particles with size of 9.2 nm. The sample had superparamagnetic behavior at room temperature. The Mossbauer results showed Fe occupancies in the A and B sites of 43 and 57 %, evidencing the formation of a partial inversed spinel. The DC and AC susceptibility data showed the presence of a spin glass phase with onset at 206 K, this magnetic phase was wiped under a field of about 4300 Oe. The electrochemical characterization showed the ability of this sample for oxygen evolution reaction applications. The HEO-600 sample showed overpotential of 358 mV at 10 mA cm- 2. This work brings new developments in the understanding of high entropy oxides and provides a useful application as an electrocatalyst in OER processes.

The escalating global demand for clean and sustainable energy necessitates the development of efficient and environmentally friendly energy conversion technologies. Protonic ceramic cells (PCCs), operating at intermediate temperatures (400-700°C), have emerged as a promising alternative to traditional fuel cells due to their ability to utilise a wide range of fuels, including hydrogen and hydrocarbons, with high efficiency and minimal pollutant emissions [1]. A critical challenge for realising the full potential of PCCs lies in enhancing the oxygen reduction reaction (ORR) at the cathode, which significantly impacts the overall cell performance. The ORR involves a complex multi-step process involving oxygen adsorption, dissociation, and charge transfer, and its sluggish kinetics often limit the fuel cell efficiency. Therefore, the development of highly active and durable oxygen electrode materials is crucial for advancing PCC technology [2]. While significant progress has been made in developing high-performance oxygen electrode materials for solid oxide cells (SOCs) operating at higher temperatures, the direct translation of these materials to the lower-temperature regime of protonic ceramic fuel cells (PCCs) remains a significant challenge [3]. One of the main problems is that many promising oxygen electrode materials developed for traditional SOCs react adversely with the state-of-the-art barium-zirconate/cerate-based proton-conducting electrolytes commonly employed in PCCs. This incompatibility, often leading to the formation of undesired phases or interfacial degradation, necessitates the exploration and development of novel electrode compositions specifically tailored for PCFC applications. Furthermore, even when chemically compatible, some SOC oxygen electrode materials exhibit insufficient activity for the water splitting/formation reactions crucial to the PCC mechanism or demonstrate instability under the high steam concentrations prevalent in PCC operation [3]. Therefore, searching for effective PCFC oxygen electrodes requires high electrocatalytic activity, robust chemical compatibility with proton-conducting electrolytes, and stability under humid atmospheres. This work focuses on Ba 2 Co 9 O 14 (BCO), a layered cobaltite, as a potential oxygen electrode material for PCFCs. BCO possesses a unique layered intergrowth structure, distinct from the state-of-the-art perovskite structure, which may offer advantages for the ORR process [4]. The layered structure can facilitate the diffusion of oxygen ions along the layers, while the mixed oxidation states of cobalt (Co 2+ /Co 3+ ) can provide active sites for the ORR [4]. Furthermore, BCO may be able to mitigate undesirable cation diffusion and minimise the concentration disparity of the alkaline-earth element within the electrolyte. Therefore, this study aims to investigate the structural, electrochemical, and electrocatalytic properties of BCO and evaluate its potential as a high-performance oxygen electrode for PCFCs. The X-ray diffraction (XRD) pattern of the synthesised BCO powder confirmed the formation of a single-phase material with a layered intergrowth structure. All the diffraction peaks could be indexed to the reported crystallographic data for Ba 2 Co 9 O 14 , indicating the absence of any impurity phases. The bond valence sum (BVS) calculation of the Co-ions indicated a mixed Co 3+ /Co 2+ charge ordering at the different Co-site positions, with an average oxidation state of +2.75. This value is close to the nominal oxidation state of +2.67 for Ba 2 Co 3 2+ Co 6 3+ O 14 [5]. Scanning electron microscopy (SEM) images revealed a platelet-like morphology of the BCO particles. The platelet-like structure can provide a large surface area for oxygen adsorption and facilitate the diffusion of oxygen species along the layers [6]. X-ray photoelectron spectroscopy (XPS) analysis confirmed the presence of Co 2+ /Co 3+ in BCO. The presence of this redox pair is believed to be crucial for enhancing the electrocatalytic activity of the material. XPS also revealed a significant concentration of oxygen vacancies on the surface of BCO. Oxygen vacancies act as active sites for oxygen reaction and diffusion at the surface and play a crucial role in the ORR [7–9]. Thermogravimetric analysis (TGA) showed excellent thermal stability of BCO in O 2 up to 800 °C, with negligible weight loss. This indicates that BCO is stable under typical PCFC operating conditions and does not undergo significant oxygen loss or phase decomposition. Interestingly, unlike some perovskite oxides that exhibit proton uptake in humid atmospheres [10], BCO did not show any significant weight gain in wet conditions, suggesting that proton incorporation into the BCO structure is minimal. The TEC values determined by dilatometry in air were in the range ~23-24 x 10 -6 °C -1 above ~350°C. This range of TEC values is typical of other Co-based oxide systems [11,12]. Electrochemical impedance spectroscopy (EIS) measurements showed that the BCO electrode exhibited a polarisation resistance ( R p ) comparable to, and in some cases lower than, state-of-the-art oxygen electrodes under similar operating conditions. The electronic leakage current through the BZY15 electrolyte plays a crucial role in accurately interpreting the electrode kinetics. The measured impedance spectra were carefully analysed to deconvolute the electrode processes from the electrolyte contribution. An appropriate equivalent circuit model was developed to account for the electronic leakage current, and the true electrode polarisation resistance was determined [13,14]. The analysis of the impedance spectra as a function of p O2 revealed that the rate-limiting step for the ORR was identified as surface oxygen diffusion towards the triple-phase boundary (TPB), where the gas phase, the electrode material, and the electrolyte meet [15]. Due to the relatively low bulk ionic conductivity of the BCO material [16], oxygen transport is primarily governed by surface diffusion along with the layered structure (Fig. 1) [6]. This highlights the importance of the platelet-like morphology observed in the SEM images, as it provides a large surface area for oxygen diffusion. Overall, this study demonstrates the potential of Ba 2 Co 9 O 14 (BCO) as a promising novel oxygen electrode material for PCFCs. The results of this study suggest that BCO is a promising candidate for replacing or complementing conventional perovskite oxygen electrodes in PCFCs. This work contributes to the development of high-performance PCFCs and paves the way for the utilisation of novel layered cobaltites for electrochemical energy conversion. Fig. 1 - Schematic representation of the oxygen reaction mechanism in BCO electrodes. Adapted from [6]. Acknowledgements The authors acknowledge the following grants/projects: 2020.02797.CEECIND/CP1589/CT0030 ( https://doi.org/10.54499/2020.02797.CEECIND/CP1589/CT0030 ), 2022.02498.PTDC ( https://doi.org/10.54499/2022.02498.PTDC ), UIDB/00481/2020 ( https://doi.org/10.54499/UIDB/00481/2020 ), and UIDP/00481/2020 ( https://doi.org/10.54499/UIDP/00481/2020 ) from Fundação para a Ciência e a Tecnologia (FCT); and CENTRO-01-0145-FEDER-022083 from Centro Portugal Regional Operational Programme (Centro2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF). Rafael A. Raimundo and Daniel A. Macedo also acknowledge the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq/Brazil, 309430/2019-4 and 151879/2022-2). This study was also financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES) – Finance Code 001. References [1] C. Duan, R.J. Kee, H. Zhu, C. Karakaya, Y. Chen, S. Ricote, A. 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alpha-Fe2WO6 (FWO) was successfully synthesized by the modified Pechini method and applied as an electrocatalyst for the oxygen evolution reaction (OER) for the first time. The FWO sample was systematically investigated by XRD, FTIR, Raman, FE-SEM/EDS, TEM, EPR and Mossbauer spectroscopy to understand its properties. FWO showed promising electrochemical performance with an overpotential of 306 mV@10 mA cm-2 and a Tafel slope of 48.5 mV dec-1, associated with the charge balance in the materials lattice involving essentially Fe3+ and W6+ cations. The catalyst exhibited excellent short-term stability for 24 h at 10 mA cm-2, indicating its potential as a cost-effective alternative for OER.