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Abstract Dendritic Li deposition on graphite anodes of Li-ion batteries (LIBs) not only deteriorates the anode performance but also causes safety concerns. We demonstrate here a proof-of-concept graphite anode containing a polymer coating that effectively mitigates Li dendrite formation under harsh lithiation conditions. It is shown that Li dendrites with dimensions ranging from a few tens nanometers to microns occur readily on granular graphite electrodes either under 20% over-lithiation at 0.2C or fast lithiation up to 10C rate. In contrast, the graphite anode with a conformal thin coating of high-polarity β-phase polyvinylidene difluoride (PVDF) on graphite particles exhibits dendrite-free Li plating under either condition. Moreover, the PVDF coated graphite anode exhibits substantially improved cycling stability with high Coulombic efficiencies under the Li-plating conditions. The rise of charge-transfer resistance due to over-lithiation is reduced. The proof of concept for adopting a dendrite-suppressing polymer coating on graphite anodes offers a new strategy for improving battery safety and renders more options for cell design in enhancing energy and power performances for the state-of-the-art LIBs. Graphical abstract Image 1 Highlights • Graphite anode with lithium dendrite suppression polymer coating is demonstrated. • Li dendrites occur readily on graphite anode under over-lithiation and fast charge. • β-phase PVDF coating effectively suppresses Li dendrite formation on graphite. • β-phase PVDF coating reduces charge-transfer resistance rise upon over-lithiation. [ABSTRACT FROM AUTHOR]

Abstract: In this study, the coking resistance of anode supported direct ethanol solid oxide fuel cell with a Ni–S x anode was investigated comparatively with the conventional cell using pure Ni catalyst. The surface catalytic properties of Ni were manipulated via depositing a layer of S atoms. It was confirmed that on the surface of Ni, a combination of S monolayer and elemental S was formed without producing Ni3S2 phase. The developed Ni–S x cell exhibited a significantly improved coke resistivity in ethanol feed while maintaining an adequately high performance. The S species on Ni enabled the suppression of the coke formation as well as the alleviation of the metal dusting effect of the anode structure. After operating in ethanol fuel for identical period of time at 850 °C, a maximum power density of 400 mW cm−2 was sustained whereas the conventional cell performance decreased to less than 40 mW cm−2 from the original 704 mW cm−2. In an optimized stability test, the Ni–S x cell operated at 750 °C for more than 22 h until the fuel drained without any degradation. [Copyright &y& Elsevier]

Abstract: Hydrogen sulfide, usually considered to be an anode catalyst poison, strongly promotes methane oxidation over sulfur resistant catalysts. The role of H2S in oxidation of sour CH4 feed over a sulfur resistant SOFC anode catalyst at 850°C has been determined through thermodynamic and experimental studies. The anode material was an intimately mixed 50/50 mass ratio composite of La0.4Sr0.6TiO3−δ and YSZ. The power density improved dramatically from 2mWcm−2 with pure CH4 as fuel to more than 450mWcm−2 for CH4 containing 20% H2S. However, H2S was not the only fuel converted, and its interaction with CH4 was the key factor in enhancement of performance. The anode effluent gas mixture included H2S, SO2, H2 and CS2 consistent with thermodynamic predictions. The role of H2S in the CH4 oxidation mechanism was determined, and showed that CH4 and H2S must be considered together as a fuel and not as two separate fuels. The types of electrochemical reactions that occurred in the fuel cell were strongly dependent on potential. [Copyright &y& Elsevier]

Abstract: The level of barium doping in lanthanum strontium titanate (La0.4Sr0.6−x Ba x TiO3, 0≤ x ≤0.2; LST, x =0; LSBT, x >0), prepared by solid state synthesis, affects its performance as anode in solid oxide fuel cells (SOFCs). Cell structures of LST and all LSBT were similar. The oxidation state of Ti in all compounds was reduced by a comparable amount when LST or LSBT was heated under reducing conditions to form La0.4Sr0.6−x Ba x Ti0.59 4+Ti0.41 3+O2.97. All fuel cells using LST or LSBT had high activity for conversion of hydrogen or methane, and the activity increased with the level of substitution by Ba. In addition, performance was enhanced when H2S was present in either CH4 or H2 fuel. There was good contact between YSZ electrolyte and each LSBT or LSB anode. [Copyright &y& Elsevier]

Abstract: Whereas Ce0.9Sr0.1Cr0.5V0.5O3 is an active fuel cell anode catalyst for conversion of only the H2S content of 0.5% H2S–CH4 at 850°C, inclusion of 5wt% NiO to form a composite catalyst enabled concurrent electrochemical conversion of CH4. A fuel cell with a 0.3mm thick YSZ membrane and Ce0.9Sr0.1Cr0.5V0.5O3 as anode catalyst had a maximum power density of 85mWcm−2 in 0.5% H2S–CH4 at 850°C, arising only from the electro-oxidation of H2S. Using a same thick membrane, promotion of the anode with 5wt% NiO increased the total anode electro-oxidation activity to afford maximum power density of 100mWcm−2 in 0.5% H2S–CH4. The same membrane provided 30mWcm−2 in pure CH4, showing that the incremental improvement arose substantially from CH4 conversion. Performance of each anode was stable for over 12h at maximum power output. XPS and XRD analyses showed that an increase in conductivity of Ce0.9Sr0.1Cr0.5V0.5O3 in H2S-containing environments resulted from a change in composition and structure from the tetragonal oxide to monoclinic Ce0.9Sr0.1Cr0.5V0.5(O,S)3. [Copyright &y& Elsevier]

Abstract: The stability and activity in 0.5% H2S–CH4 of Ce0.9Sr0.1VO3 and Ce0.9Sr0.1VO4 anode materials for H2S-containing CH4 fueled SOFCs have been determined. XRD showed that Ce0.9Sr0.1VO4 was reduced when the fuel gas was 0.5% H2S–CH4, while Ce0.9Sr0.1VO3 remained stable over 24h at 950°C. Electrochemical tests in 0.5% H2S–CH4 showed stable performance at 950 and 800°C for cells comprising Ce0.9Sr0.1VO3|YSZ|Pt. Comparison of fuel cell performances using 0.5% H2S–CH4, 0.5% H2S–N2 and 5% H2S–N2 as feeds showed that Ce0.9Sr0.1VO3 was not active for oxidation of methane, but highly active for conversion of H2S. Electrochemical impedance results were consistent with the finding that the anode was activated only in an environment that contained H2S. Conductivity measurements showed there was an increase in conductivity in H2S-containing environments, and that this increase resulted from a change in composition and structure from the oxide to monoclinic Ce0.9Sr0.1V(O,S)3, as evidenced by XPS and XRD analyses. [Copyright &y& Elsevier]

Abstract: Au/MoS2 is a promising anode catalyst for conversion of all components of H2S-containing syngas in solid oxide fuel cell (SOFC). MoS2-supported nano-Au particles have catalytic activity for conversion of CO when syngas is used as fuel in SOFC systems, thus preventing poisoning of MoS2 active sites by CO. In contrast to use of MoS2 as anode catalyst, performance of Au/MoS2 anode catalyst improves when CO is present in the feed. Current density over 600mAcm−2 and maximum power density over 70mWcm−2 were obtained at 900°C, showing that Au/MoS2 could be potentially used as sulfur-tolerant catalyst in fuel cell applications. [Copyright &y& Elsevier]

Protonic ceramic ethane fuel cells fed by hydrocarbon fuels are demonstrated to be effective energy conversion devices. However, their practical application is impeded by a lack of anode materials combining excellent catalytic activity with good chemical stability and anti‐carbon deposition properties. In this work, in which Sr2Fe1.5Mo0.5O6‐δ (SFM) double perovskite oxide is used as the matrix framework, catalytic activity toward H2 and C2H6 oxidation is systematically investigated using Ba‐doping. It is found that the concentration of the oxygen vacancy is gradually improved with increased Ba content to significantly enhance catalytic activity toward H2 and C2H6 oxidation. From the series studied, Ba0.6Sr1.4Fe1.5Mo0.5O6‐δ exhibits the highest catalytic activity, while the power densities of the electrolyte‐supported Ba0.6SFM/BaCe0.7Zr0.1Y0.2O3‐δ (BCZY)/La0.58Sr0.4Co0.2Fe0.8O3‐δ (LSCF)‐Sm0.2Ce0.8O2‐δ (SDC) single cell reach 205 and 138 mW cm–2 at 750°C in H2 and C2H6, respectively. The ethane conversion rate of the experimental cell is shown to reach 38.4%, while simultaneously maintaining ethylene selectivity at 95%. Furthermore, the single cell exhibits no significant attenuation during stable operation for 20 h, as well as demonstrating excellent anti‐coking performance. The proposed results suggest that Ba0.6Sr1.4Fe1.5Mo0.5O6‐δ represents a promising anode material for efficient hydrocarbon‐related electrochemical conversion to realize the coproduction of ethylene and power in protonic ceramic ethane fuel cells. [ABSTRACT FROM AUTHOR]

A La 0.5 Sr 0.5 Fe 0.9 Mo 0.1 O 3-δ -CeO 2 (LSFM-CeO 2) composite was prepared by impregnating CeO 2 into porous La 0.5 Sr 0.5 Fe 0.9 Mo 0.1 O 3-δ perovskite and was used as an anode material for proton-conducting solid oxide fuel cells (SOFCs). The maximum power densities of the BaZr 0.1 Ce 0.7 Y 0.2 O 3-δ (BZCY) electrolyte-supported single cell with LSFM-CeO 2 as the anode reached 291 mW cm−2 and 190 mW cm−2 in hydrogen and ethane fuel at 750 °C, respectively, which are significantly higher than those of a single cell with only LSFM as the anode. Additionally, the ethylene selectivity and ethylene yield from ethane for the fuel cell at 750 °C were as high as 93.4% and 37.1%, respectively. The single cell also showed negligible degradation in performance and no carbon deposition during continuous operation for 22 h under an ethane fuel atmosphere. The improved electrochemical performance due to the impregnation of CeO 2 can be a result of enhanced electronic and ionic conductivity, abundant active sites, and a broad three-phase interface in the resultant composite anode. The LSFM-CeO 2 composite is believed to be a promising anode material for proton-conducting SOFCs for co-producing electricity and high-value chemicals from hydrocarbon fuels. [ABSTRACT FROM AUTHOR]

Abstract: The system LSBT/YSZ (LSBT is La0.4Sr0.5Ba0.1TiO3) is a promising combination as an anode material for full ceramic SOFCs. An anode comprising a porous layer of YSZ impregnated with LSBT shows good performance for conversion of high sulfur content fuels. The microstructures within the composite matrix were determined and correlated with the parameters of the production process. The anodes were characterized electrochemically using impedance spectroscopy (EIS) and potentiodynamic tests performed at 850 °C with various fuels to determine the effect of H2S in the feeds: H2, H2/H2S (5000 ppm), CH4, CH4/H2S (5000 ppm). The highest power densities (200 mW cm−2 in H2/H2S) were obtained for LSBT/YSZ composites after impregnation six times with LSBT, corresponding to 12.6 wt% LSBT; further impregnations dramatically decreased performance as a result of restricted access of fuel to active sites. [Copyright &y& Elsevier]

Abstract: Undoped BaTiO3 perovskite oxide is more effective than SrTiO3 and La2Ti2O7 oxide as anode catalyst in SOFC fueled with H2S-containing methane. Electrochemical performance, impedance spectroscopy and other characterizations show that pure BaTiO3 is a good anode catalyst for conversion of methane in SOFC, especially in H2S-containing atmospheres. Compared with SrTiO3 and La2Ti2O7 samples, the BaTiO3−based fuel cell has higher resistance to carbon deposition, better electrochemical performance and much higher stability during long term operation. A maximum power density of 135 mW cm−2 was achieved at 900 °C with 0.5% H2S–CH4 in a fuel cell having a 300 μm thick YSZ electrolyte. High catalytic activity for methane conversion, mixed electronic and ionic conductivity, and the surface basicity of BaTiO3 unexpectedly provides promising performance as anodes in SOFC. [Copyright &y& Elsevier]

Abstract: Ethane and electrical power are co-generated in proton ceramic fuel cell reactors having Cr2O3 nanoparticles as anode catalyst, BaCe0.8Y0.15Nd0.05O3−δ (BCYN) perovskite oxide as proton conducting ceramic electrolyte, and Pt as cathode catalyst. Cr2O3 nanoparticles are synthesized by a combustion method. BaCe0.8Y0.15Nd0.05O3−δ (BCYN) perovskite oxides are obtained using a solid state reaction. The power density increases from 51mWcm−2 to 118mWcm−2 and the ethylene yield increases from about 8% to 31% when the operating temperature of the solid oxide fuel cell reactor increases from 650°C to 750°C. The fuel cell reactor and process are stable at 700°C for at least 48h. Cr2O3 anode catalyst exhibits much better coke resistance than Pt and Ni catalysts in ethane fuel atmosphere at 700°C. [ABSTRACT FROM AUTHOR]

The hollow Si nanospheres modified by the mechanically robust titanium dioxide (TiO 2 ) shell and the uniform carbon layer are intentionally designed and successfully prepared as the anode active material of high performance lithium-ion batteries. The effects of the robust TiO 2 shell and the uniform carbon layer on the structure and electrochemical performances for the Si@TiO 2 @C nanospheres are studied in detail by X-ray photoelectron spectroscopy, transmission electron microscopy, X-ray diffraction and charge/discharge tests. The results show that the hollow structure of the Si core can spontaneously absorb the huge volume expansion stress, the robust TiO 2 shell is used as a compact fence to promote the expansion towards the interior of the Si cavity instead of the exterior in the processes of charge/discharge, and the uniform carbon layer can effectively enhance the electrical conductivity and further control the integrity and stability of the well-wrapped core-shell-shell framework. Typically, the resultant hollow Si@TiO 2 @C nanospheres exhibit a high initial discharge capacity of 2557.1 mAh g −1 with coulombic efficiency of 86.06% as well as a large recuperative discharge capacity of 1270.3 mAh g −1 after 250 cycles at 1 A g −1 with a mean coulombic efficiency of 99.53%. Therefore, the hollow Si@TiO 2 @C nanospheres prepared by one-step sol-gel coating process show outstanding electrochemical properties and are considered as a prospective candidate to the adhibitions of the anode material for new generation power LIBs. [ABSTRACT FROM AUTHOR]

In situ exsolution of Co nanoparticles on perovskite framework has been successfully synthesized by firing the porous precursor SrMo 0.8 Co 0.1 Fe 0.1 O 3-δ (SMCFO) in reducing flow at 850 °C. A structure transformation (from mixed to pure cubic phase) and the growth of Co nanoparticles are observed in H 2 atmosphere. This leads to an increase in the oxygen vacancy content, which is beneficial to the electrical conduction and catalytic activity towards the oxidations of H 2 and C 2 H 6 . Moreover, this material exhibits good redox reversibility under the condition of multiple reduction and re-oxidation cycles, as confirmed by the thermogravimetric analysis (TGA) measurements. A protonic fuel cell (PFC) built with this newly developed material shows a comparable electrocatalytic activity in both C 2 H 6 and H 2 atmospheres while a considerably high power density of 377 mW cm −2 is achieved in H 2 and 268 mW cm −2 in C 2 H 6 at 750 °C. In addition, C 2 H 4 yield in the cell with Co-SMCFO as anode is considerably improved (11.9%–37.8% at 650–750 °C) with respect to the widely used chromium oxide. The good electrochemical performance, the improved C 2 H 6 partial dehydrogenation ability and the negligible carbon formation in the Co-SMCFO anode are the strong indications that the SMCFO is a promising catalyst for the cogeneration of C 2 H 4 and electricity, and can also be potentially utilized in the PFC directly fueled with hydrocarbon. [ABSTRACT FROM AUTHOR]

The ideal solid oxide fuel cells (SOFCs) can be powered by readily available hydrocarbon fuels containing impurities. While this is commonly recognized as a key advantage of SOFC, it also, together with the elevated operating temperature, becomes the main barrier impeding the in-situ or operando investigations of the anode surface chemistry. Here, using a well-designed quenching experiment, we managed to characterize the near-surface structure of La 0.4 Sr 0.6 TiO 3+δ (LST) anode in SOFCs fuelled by H 2 S-containing methane. This new method enabled us to clearly observe the surface amorphization and sulfidation of LST under simulated SOFC operating conditions. The ∼1 nm-thick two dimensional sulfur-adsorbed layer was on top of the disordered LST, containing –S, –SH and elemental sulfur species. In SOFC test, such “poisoned” anode showed increased performances: a ten-fold enhanced power density enhancement (up to 30 mW cm −2 ) and an improved open circuit voltage (from 0.69 V to 1.17 V). Moreover, its anodic polarization resistance in methane decreased to 21.53 Ω cm 2 , a difference of 95% compared with the sulfur-free anode. Control experiments confirmed that once the adsorbed sulfur species were removed electrochemically, methane conversion slowed down simultaneously till full stop. [ABSTRACT FROM AUTHOR]

A layered Mo doped Pr 0.5 Ba 0.5 MnO 3−δ (Mo-PBMO) double perovskite oxide was prepared by a modified sol–gel method and the properties of the fabricated material are characterized by various technologies. The results of X-ray diffraction (XRD), H 2 -temperature programmed reduction (H 2 -TPR), NH 3 -temperature programmed desorption (NH 3 -TPD), and thermogravimetric analysis (TGA) demonstrate that the treatment in reducing atmosphere at high temperature lead to a significant phase transformation of the material to a single cubic phase as well as with the Mo in multiple oxidized states. Such character leads to the production of large amount of oxygen deficiency with facilitated oxygen diffusion. The electrochemical performance tests of half-cell and single cell SOFCs exhibit the promoted effect of Mo on catalytic activity for the oxidation of H 2 and CH 4 , indicating that Mo-PBMO could serve as an anode material candidate for SOFCs. [ABSTRACT FROM AUTHOR]

A site deficient La 0.2 Sr 0.7 TiO 3−δ (LST A ) and a highly proton conductive electrolyte BaCe 0.7 Zr 0.1 Y 0.2 O 3−δ (BCZY) are synthesized by using solid state reaction method. The performance of the electrolyte-supported single cell, comprised of LST A + Cr 2 O 3 + Cu//BCZY//(La 0.60 Sr 0.40 ) 0.95 Co 0.20 Fe 0.80 O 3−δ (LSCF)+BCZY, is fabricated and investigated. LST A shows remarkably high electrical performance, with a conductivity as high as 27.78 Scm −1 at 1150 °C in a 10% H 2 /N 2 reducing atmosphere. As a main anode component, it shows good catalytic activity towards the oxidation of ethane, causing the power density to considerably increase from 158.4 mW cm −2 to 320.9 mW cm −2 and the ethane conversion to significantly rise from 12.6% to 30.9%, when the temperature increases from 650 °C to 750 °C. These changes agree well with the polarization resistance which dramatically decreases from 0.346 Ωcm 2 to 0.112 Ωcm 2 . EDX measurement shows that no element diffusion exists (chemical compatibility) between anode (LST A + Cr 2 O 3 +Cu) and electrolyte (BCZY). With these properties, the pure phase LST A is evaluated as a high electro-catalytic activity anode material for ethane proton conducting solid oxide fuel cell (PC-SOFC). [ABSTRACT FROM AUTHOR]

Active anodes were fabricated via wet chemical impregnation of optimized amount of La 0.4 Sr 0.6 TiO 3 (L4ST) into La 0.4 Ce 0.6 O 1.8 (LDC) pre-infiltrated porous yttria-stabilized zirconia (YSZ) matrix. Impregnations of 10 wt% LDC with 16 wt% L4ST significantly improved the performance of the fuel cell from 48 mW cm −2 for pure L4ST to 161 mW cm −2 for LDC–L4ST at 900 °C in H 2 . The contribution of the pre-loaded LDC to this improvement was investigated using electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) as well as transmission electron microscopy (TEM). The measurement results indicated that pre-infiltrated LDC increased the activity of the anode more effectively by decreasing the total polarization resistance of the cell from 3.3 Ω cm 2 to 1.0 Ω cm 2 in humidified H 2 at 900 °C. More importantly, the LDC nano-deposits (<20 nm) behaved as an effective “adhesive” that substantially enhanced the wettability of L4ST on YSZ matrix, resulting in finer and more uniform structure of L4ST infiltrates. The LDC–L4ST cells also demonstrated significantly improved performances in 0.5% H 2 S–H 2 and 0.5% H 2 S–CH 4 with higher stability than cells with pure L4ST anode. [ABSTRACT FROM AUTHOR]

Abstract: The effects of H2S and H2O in the methane feed on carbon deposition in a La0.4Sr0.5Ba0.1TiO3 (LSBT) anode-based solid oxide fuel cell were investigated in this work under different operating conditions. Characterization was done using a combination of electrochemical, Fourier transform infra-red spectroscopy (FTIR), temperature-programmed oxidation (TPO) and X-ray photoelectron spectroscopy (XPS) measurements. As expected, carbon accumulation became more severe with increasing exposure time and operating temperature, but less severe in the presence of a current and/or steam. Addition of 0.5% H2S to the feed increased carbon accumulation and this carbon could not be removed effectively by co-feeding a small amount of steam to the anode. The resulting carbon was, however, easier to remove with oxygen as compared to that deposited by the H2S-containing dry feed. [Copyright &y& Elsevier]

Ethane can be electrochemically dehydrogenated and converted into electric energy via protonic ceramic fuel cells to obtain highly selective chemical ethylene without producing carbon oxides. This novel conversion path relies on a highly catalytically active anode for promote the cracking of ethane. In responding to this requirement, a previously characterized anode material (La 0.6 Sr 0.4) 0.95 Fe 0.9 Mo 0.1 O 3-δ (LSFM) is modified by doping with active metals (Ni and Co) at the B-site of a perovskite structure. The (La 0.6 Sr 0.4) 0.95 Fe 0.7 Ni 0.2 Mo 0.1 O 3-δ (LSFNM), (La 0.6 Sr 0.4) 0.95 Fe 0.7 Co 0.2 Mo 0.1 O 3-δ (LSFCM) and (La 0.6 Sr 0.4) 0.95 Fe 0.7 Co 0.1 Ni 0.1 Mo 0.1 O 3-δ (LSFCNM) electrode materials are synthesized by the combustion method. The subsequent in situ exsolution of the FeNi, CoFe and NiCoFe alloy nanoparticles in a reducing atmosphere improves the catalytic performance of the resultant electrodes. The obtained data show that the maximum power densities of single cells constructed using LSFCNM as an anode material at 750 °C reach 328 mW cm−2 and 258 mW cm−2 in H 2 and C 2 H 6 , respectively. Meanwhile, the ethane conversion process yields ∼44% under a constant current. The significantly higher performance of these cells than that achieved with single cells using LSFNM and LSFCM as anode materials, respectively, indicate that the NiCoFe ternary alloy offers better synergistic catalytic activity than that of the CoFe and FeNi binary alloys. [Display omitted] •In situ precipitation ternary alloys by doping active metals Ni and Co elements. •The segregation of nanoparticles obtains abundant active oxygen vacancies. •The thermal catalytic and electrochemical properties are significantly improved. •Ethylene and electricity can be coproduced in ethane-fueled protonic ceramic fuel cells. [ABSTRACT FROM AUTHOR]

Anode materials with excellent catalytic activity, good stability, and enhanced tolerance to carbon deposition are highly desired for solid oxide fuel cells (SOFCs). Herein, CoFe (CF) nanoalloy catalysts are homogeneously in-situ embedded on Sr 3 FeMoO 7 (RP-SFM) efficient electrically conductive perovskite matrix through reduction of Sr 2 FeMo 2/3 Co 1/3 O 6−δ precursor. The particle size of CoFe alloy is in the range of 10–50 nm, and the electrical conductivity enhances from about 8 to 17 S cm−1 to 49-63 S cm−1 after Sr 2 FeMo 2/3 Co 1/3 O 6−δ reduction. The maximum power density of SOFCs with the RP-SFM@CF-SDC(Sm 0.2 Ce 0 · 8 O 1.9) composite anode in H 2 fuel reaches to 2.12 W cm−2 at 850 °C, which is about 1.4 times than that of the SOFCs with traditional Ni-SDC anode. Moreover, the RP-SFM@CF-SDC anodes also demonstrate excellent resistance to carbon deposition and high power density when C 3 H 8 hydrocarbon is used as fuel. The improved catalytic activity results from the efficient electronic/ion conductive paths, abundant CoFe active sites, together with the enlarged trip phase boundaries (TPBs). Image 1 • CoFe(CF) nanoalloy are homogeneously embedded on the layered perovskite RP-SFM. • RP-SFM@CF anode exhibits excellent catalytic activity and good structural stability. • RP-SFM@CF-SDC anode exhibits higher electrochemical performance than Ni-SDC. • The improved performance results from the abundant CoFe active sites and TPBs. [ABSTRACT FROM AUTHOR]