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Achieving high performance and stability in cathodes for the oxygen reduction reaction is crucial for the advancement of proton ceramic fuel cells (PCFCs). The introduction of non-metal doping method presents an opportunity to simultaneously optimize the perovskite structure and augment the activity and stability of the oxygen reduction reaction. Herein, we develop a phosphorus-doped SrCo 0·8 Fe 0·15 P 0·05 O 3-δ (SCFP) cathode for PCFCs. The SCFP cathode shows a low area specific resistance of 0.24 Ω cm2 at 650 °C in wet air (5% H 2 O), which is smaller than that of the phosphorus-free SrCo 0·8 Fe 0·2 O 3-δ (SCF) electrode (0.34 Ω cm2). The Ni–BaZr 0.1 Ce 0·7 Y 0.1 Yb 0.1 O 3-δ (BZCYYb) anode-supported single cell with BZCYYb electrolyte and SCFP cathode exhibits a superior performance of 865 mW cm−2 at 650 °C under H 2 atmosphere. This underscores the effectiveness of the phosphorus-doping strategy as a promising approach for advancing cathode development in PCFCs. [Display omitted] [ABSTRACT FROM AUTHOR]

Ammonia (NH 3), a promising carbon-free energy carrier, can be directly and efficiently converted into electricity in solid oxide fuel cells (SOFCs). However, the NH 3 -fueled SOFC (NH 3 –SOFC) still suffered from several difficulties, including sluggish oxygen reduction reaction (ORR) kinetics and poor cathode durability. In this study, we develop a LSCF-GDC dual-phase cathode with uniform distribution for NH 3 –SOFC. In comparison with commercial counterpart, the dual-phase cathode shows a lower ORR resistance of 0.114 Ω cm2 for at 700 °C due to reduced grain sizes and expanded triple-phase boundary (TPB) length. The resultant NH 3 –SOFC follows the H 2 oxidation process and delivers a comparable peak power density of 0.347 Wcm−2 to H 2 –SOFC at 700 °C, which is further improved to 0.516 Wcm−2 after 280 h activation at 0.7 V. Further operation of five thermal cycles between 700 and 500 °C results in a performance degradation, which can be explained by the microstructure changes of Ni-based anode rather than the dual-phase cathode. Moreover, the thermal cycled NH 3 –SOFC can maintain stable operation without current decay at constant 700 °C and 0.7 V in the subsequent 135 h, further demonstrating the robustness of the dual-phase cathode. Therefore, the introduction of GDC into self-assembled dual-phase cathode is an effective way to synergistically promote the electrochemical activity and durability of the cathode for NH 3 –SOFC. [ABSTRACT FROM AUTHOR]

The catalytic efficiency of the cathode is paramount in elevating the operational efficacy of low-temperature solid oxide fuel cells (LT-SOFCs) through expeditious facilitation of the oxygen reduction reaction (ORR). Cathode confronts formidable challenges due to oxygen reduction reaction (ORR) kinetics. This work aims to develop a high-performance cathode by doping strontium (Sr) into Nd 2- x Sr 2 x NiO 4. We synthesized a series of Nd 2- x Sr 2x NiO 4 (x : 0, 0.03, 0.06, 0.1) samples with varying Sr doping levels and evaluated their electrochemical performances. Nd2- x Sr 2 x NiO 4 with optimal ratio (x : 0.06) delivers the highest peak power density of 620–338 mw cm−2 at 550-470 °C among all four samples. The electrochemical impedance spectroscopy of the optimal composition revealed that Nd 2- x Sr 2 x NiO 4 exhibits low electrode polarization resistance of 0.34 Ω cm 2 , depicting its high catalytic performance and compatibility with the electrolyte and anode. Furthermore, XPS spectra also suggest higher surface oxygen vacancies than the other three samples, subsequently improving the conductivity and catalytic activity. Along with high power and OCVs, Nd 2- x Sr 2 x NiO 4 cathode-based SOFC is persistently stable for 40 h without significant degradation. These results conclusively point to demonstrating Nd 2- x Sr 2 x NiO 4 as a high-performing cathode for LT-SOFCs. [ABSTRACT FROM AUTHOR]

Double perovskite oxide Pr 1-x Nd x BaFe 2 O 5+δ (PNBFx, x = 0.0–0.3) nanofiber were prepared using electrospinning and were evaluated as cathodes for solid oxide fuel cells (SOFCs). The crystalline structure, microstructure, and electrochemical performance of PNBFx were thoroughly investigated and discussed. The PNBFx nanofiber cathodes obtained after sintering at 800 °C crystallized in a tetragonal structure with the space group P 4/ mmm and had good chemical compatibility with SDC electrolytes at 900 °C for 4 h. Nd doping was found to increase the lattice parameter, while the average valence of praseodymium and iron content increased steadily in PNBFx. The Pr 0.8 Nd 0.2 BaFe 2 O 5+δ (PNBF02) nanofiber cathode exhibited the best performance with a polarization resistance (R p) of 0.072 Ω cm2 at 750 °C. When PNBF02 nanofiber was used as a single-cell cathode, the peak power density reached 1.52 W cm2 at 750 °C. All results indicate that double perovskite PNBF02 is a promising cathode material for SOFCs. [ABSTRACT FROM AUTHOR]

The sluggish kinetics of the oxygen reduction reaction (ORR) and susceptibility to CO 2 poisoning present significant challenges in the application of intermediate temperature solid oxide fuel cells (IT-SOFCs). In this study, bismuth (Bi) was introduced as a dopant for the first time to enhance both the ORR activity and CO 2 tolerance of PrBaCoCuO 5+ δ (PBCCO) cathode. Bi doping serves to concurrently modulate the oxygen vacancy content and carrier concentration. This dual regulation enhances the processes of oxygen adsorption, dissociation, and charge transfer, as evidenced by the distribution of relaxation time (DRT) technique. Furthermore, PBBCCO demonstrates exceptional CO 2 tolerance and remarkable performance recovery following exposure to CO 2 -induced degradation. At 800 °C, the polarization resistance (R p) and maximum power density (MPD) of PBBCCO were 0.026 Ω cm2 and 631 mW cm−2, respectively. Notably, R p was reduced by 52.45%, and MPD exhibited an improvement of 45.11% at 800 °C. These findings highlight the significant impact of Bi doping on the performance of the PBCCO double perovskite cathode, underscoring its crucial importance for future developments of novel cathode materials. [ABSTRACT FROM AUTHOR]

Li-O2 batteries are considered a highly promising energy storage solution. However, their practical implementation is hindered by the sluggish kinetics of the oxygen reduction (ORR) and oxygen evolution (OER) reactions at cathodes during discharging and charging, respectively. In this work, we investigated the catalytic performance of Wn+1Cn and Wn+1CnO2 MXenes (n = 1, 2, and 3) as cathodes for Li-O2 batteries using first principles calculations. Both Wn+1Cn and Wn+1CnO2 MXenes show high conductivity, and their conductivity is further enhanced with increasing atomic layers, as reflected by the elevated density of states at the Fermi level. The oxygen functionalization can change the electronic properties of WC MXenes from the electrophilic W surface of Wn+1Cn to the nucleophilic O surface of Wn+1CnO2, which is beneficial for the activation of the Li-O bond, and thus promotes the Li+ deintercalation during the charge–discharge process. On both Wn+1Cn and Wn+1CnO2, the rate-determining step (RDS) of ORR is the formation of the (Li2O)2* product, while the RDS of OER is the LiO2* decomposition. The overpotentials of ORR and OER are positively linearly correlated with the adsorption energy of the RDS LixO2* intermediates. By lowering the energy band center, the oxygen functionalization and increasing atomic layers can effectively reduce the adsorption strength of the LixO2* intermediates, thereby reducing the ORR and OER overpotentials. The W4C3O2 MXene shows immense potential as a cathode catalyst for Li-O2 batteries due to its outstanding conductivity and super-low ORR, OER, and total overpotentials (0.25, 0.38, and 0.63 V). [ABSTRACT FROM AUTHOR]

Samaria-doped ceria (SDC) overlayers were deposited on Ag cathodes by sputtering. The SDC sputtering time was varied to investigate the properties of the Ag–SDC overlayer cathode-coated fuel cells depending on the thickness of the SDC overlayers. Among the fabricated fuel cells, Ag with a 10-nm-thick SDC overlayer (Ag-SDC10) cathode-coated fuel cell exhibited the highest peak power density of 6.587 mW/cm2 at 450 °C, showing higher performance than a pristine Pt-coated fuel cell. Moreover, electrochemical impedance spectroscopy revealed that the Ag-SDC10 cathode-coated fuel cell significantly mitigated polarization loss originating from enhanced oxygen reduction reaction kinetics compared to the pristine Ag-coated fuel cell. [ABSTRACT FROM AUTHOR]

[Display omitted] Lowering the operating temperatures of solid-oxide fuel cells (SOFCs) is critical, although achieving success in this endeavor has proven challenging. Herein, Bi 0.15 Sr 0.85 Co 0.8 Fe 0.2 O 3−δ (BiSCF) is systematically evaluated as a carbon dioxide (CO 2)-tolerant and highly active cathode for SOFCs. BiSCF, which features Bi3+ with an ionic radius similar to Ba2+, exhibits activity (e.g., 0.062 Ω cm2 at 700 °C) comparable to that of Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3−δ and PrBaCo 2 O 5+δ , while demonstrating a considerable advantage over Bi-doped cathodes. Moreover, BiSCF exhibits long-term stability over a period of 500 h, and an anode-supported cell with BiSCF achieves a power density of 912 mW cm−2 at 650 °C. The CO 2 -poisoned BiSCF exhibits quick reversibility or slight activation after returning to normal conditions. The exceptional CO 2 tolerance of BiSCF can be attributed to its reduced basicity and high electronegativity, which effectively restrict surface Sr diffusion and hinder subsequent carbonate formation. These findings highlight the substantial potential of BiSCF for SOFCs operating below 700 °C. [ABSTRACT FROM AUTHOR]

Proton exchange membrane fuel cells (PEMFCs), which have the advantages of high-power density, zero emission, and low noise, are considered ideal electrochemical conversion systems for converting hydrogen (H2) and oxygen (O2)/air into electricity. However, the oxygen reduction reaction (ORR), which is accompanied by multiple electrons, results in voltage loss and low conversion efficiency of PEMFCs. Currently, PEMFCs mainly use highload precious platinum (Pt) to promote the ORR process; however, the high cost of Pt hinders the widespread commercialization of PEMFCs. Over the past few years, metal-nitrogen-carbon single-atom catalysts (M-N-C SACs) have attracted considerable attention and have been recognized as potential Pt-based catalysts owing to their outstanding ORR activity. This review briefly introduces the components of PEMFCs. Second, we discuss the catalytic mechanisms of the M-N-C SACs for the ORR. Third, the latest advances in noble, non-noble, and heteroatom-doped M-N-C SACs used as ORR and PEMFCs cathode catalysts are systematically reviewed. In summary, we have outlined the current challenges and proposed a future perspective of M-N-C SACs for PEMFCs cathodes. [ABSTRACT FROM AUTHOR]

Co-based perovskite cathodes have demonstrated impressive catalytic activity for oxygen reduction reaction (ORR) at intermediate temperatures. However, these cathodes face the challenges such as high cost and thermal expansion coefficient (TEC) mismatch. On the other hand, Fe-based perovskite oxides like LaFeO 3 exhibit more stable properties and lower TEC, but their ORR activity is not as remarkable as that of Co-based cathodes. In this study, La3+ at the A-site of LaFeO 3 was substituted by aliovalent alkaline-earth metal cations. The research findings reveal that the doping of alkaline-earth metal ions induces the formation of structural defects and alters the valence state of Fe. This leads to an increase in the conductivity and oxygen vacancy concentration, which are critical for ORR kinetics in both H–SOFC and O–SOFC. Among the various dopants, Sr doped LaFeO 3 (LSrF) exhibits the most outstanding ORR catalytic activity. This can be attributed to its highest total conductivity, O2− conductivity, oxygen surface exchange coefficient, and oxygen bulk diffusion coefficient. At 700 °C, single cell with LSrF cathode achieves peak power densities of 0.781 and 0.894 W cm−2, for O2--conducting solid oxide fuel cell (SOFC) and H+-conducting SOFC, respectively. These performances are essentially twice that of single cell with LaFeO 3 cathode. The findings of this study provide valuable insights into doping strategies for Fe-based perovskite cathodes and contribute to the advancement of IT-SOFC cathode research. [ABSTRACT FROM AUTHOR]

In this work, Ni-doped LiMn 2 O 4 spinel oxides were studied as the cathode materials of low temperature proton ceramic fuel cell. Increasing the content of doping Ni to 0.5, the calculated active energy of the polarization process of the cell decreased from 0.62 to 0.49 eV. The cell performance increased with the Ni doping of LiMn 2 O 4 cathode, and the optimal power density reached to 547 mW cm−2 at 550 °C with a low polar resistance of 0.42 Ω cm2 for LiNi 0.5 Mn 1.5 O 4. Ni partially replacing Mn at the B site could increase the content of Mn4+, resulting in the increase of oxygen vacancy content to maintain the charge balance, which is beneficial to the oxygen reduction reaction. These results demonstrate that spinel oxide could be a promising cathode material with highly oxygen reduction activity for advanced low temperature solid ceramic fuel cells. [ABSTRACT FROM AUTHOR]

Studying the ORR activity of platinum-based electrocatalysts is an urgent task in the development of materials for proton-exchange membrane fuel cells. The catalytic ink composition and the formation technique of a thin layer at the RDE play a significant role in studying ORR activity. The use of a polymer ionomer in the catalytic ink provides viscosity as well as proton conductivity. Nafion is widely used as an ionomer for research both at the RDE and in the MEA. The search for ionomers is a priority task in the development of the MEA components to replace Nafion. The study also considers the possibility of using the LF4-SK polymer as an alternative ionomer. The comparative results on the composition and techniques of applying the catalytic layer using LF4-SK and Nafion ionomers are presented, and the influence of the catalytic ink composition on the electrochemical characteristics of commercial platinum–carbon catalysts and a highly efficient platinum catalyst based on an N-doped carbon support is assessed. [ABSTRACT FROM AUTHOR]

The application of cobalt-based perovskite cathode materials in proton-conducting SOFCs (H–SOFCs) is challenged by their high thermal expansion coefficient (TEC). To address interface degradation/separation between the cobalt-based perovskite cathode and the proton-conducting electrolyte, we design and prepare the high-entropy perovskite oxide (HEPO) BaCo 0.2 Zn 0.2 Ga 0.2 Zr 0.2 Y 0.2 O 3-δ (BCX) as the cathode for proton-conducting SOFCs (H–SOFCs). BCX demonstrates remarkable performance and stability in the oxygen reduction reaction, validated through structural analysis and electrochemical characterizations. The TEC of BCX is as low as 12.75 × 10-6 K−1 compared to the 18.69 × 10-6 K−1 of the un-doped BaCoO 3-δ (BC). The polarization resistance of BCX cathode about 0.69 Ω cm2 is realized at 600 °C, much lower than that for pristine BC cathode (1.27 Ω cm2). Cell with BCX cathode exhibits remarkable long-term stability without detectable degradation over 100 h. [ABSTRACT FROM AUTHOR]

Due to their great efficiency, low cost and pollution, and flexible fuel choice, solid oxide fuel cells (SOFCs) have been applied to energy conversion filed. However, one challenge for developing SOFCs is sluggish oxygen reduction reaction (ORR) rate. Herein, a series of Ruddlesden-Popper-type Sr 2.7 Pr 0.3 Fe 2– x Cu x O 7– δ (SPFC x) oxides are successfully synthesized and thoroughly assessed as potential SOFCs cathodes. Among all compositions, Sr 2.7 Pr 0.3 Fe 1 · 9 Cu 0 · 1 O 7– δ (SPFC10) possesses the best electrocatalysis performance and improved oxygen reduction kinetics, with the lowest polarization resistance (R p , 0.13 Ω cm2) at 700 °C. Cu-doping will contribute to improving oxygen transport kinetics, increasing oxygen vacancy concentration, and O 2p band centers close to the Fermi level, hence, enhancing the electrocatalysis performance. At 700 °C, the maximum output of the single cell with SPFC10 cathode is 704 mW cm−2. These results highlight a highly active SPFC10 cathode with Ruddlesden-Popper structure for SOFCs. [ABSTRACT FROM AUTHOR]

This work investigates a new nanostructured gas diffusion layer (nano-GDL) to improve the performance of air cathode single-chamber microbial fuel cells (a-SCMFCs). The new nano-GDLs improve the direct oxygen reduction reaction by exploiting the best qualities of nanofibers from electrospinning in terms of high surface-area-to-volume ratio, high porosity, and laser-based processing to promote adhesion. By electrospinning, nano-GDLs were fabricated directly by collecting two nanofiber mats on the same carbon-based electrode, acting as the substrate. Each layer was designed with a specific function: water-resistant, oxygen-permeable polyvinylidene-difluoride (PVDF) nanofibers served as a barrier to prevent water-based electrolyte leakage, while an inner layer of cellulose nanofibers was added to promote oxygen diffusion towards the catalytic sites. The maximum current density obtained for a-SCMFCs with the new nano-GDLs is 132.2 ± 10.8 mA m−2, and it doubles the current density obtained with standard PTFE-based GDL (58.5 ± 2.4 mA m−2) used as reference material. The energy recovery (EF) factor, i.e., the ratio of the power output to the inner volume of the device, was then used to evaluate the overall performance of a-SCMFCs. a-SCMFCs with nano-GDL provided an EF value of 60.83 mJ m−3, one order of magnitude higher than the value of 3.92 mJ m−3 obtained with standard GDL. [ABSTRACT FROM AUTHOR]

Rechargeable Zn–air batteries (ZABs) can play a significant role in the transition to a cleaner and more sustainable energy system due to their high theoretical energy density, high cell voltage, and environmental friendliness. ZAB's air cathode is the principal determinant in predicting the battery's overall performance, as it is responsible for catalyzing the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) during the discharging and charging process, respectively. In this work, a detailed optimization study of the architecture of the air cathode was carried out using the benchmark bifunctional oxygen electrocatalyst (Pt/C-RuO2). The air cathode composition and architecture were optimized regarding the choice of the commercial gas diffusion layer (GDL), the effect of hot pressing the catalyst layer (CL), and the optimum pore size of the current collector. The best cathode from this study shows a maximum power density (PDmax) of 167 mW/cm2, with a round trip efficiency and a voltage gap (Egap) of 59.8% and 0.78 V, respectively, indicating the air cathodes preparation approach proposed in this work as a promising strategy for the improvement of the overall performance of ZABs. [ABSTRACT FROM AUTHOR]

The correlation between lattice strain induced by metal dispersion into grain and the cathodic overpotential is studied for increasing oxygen‐dissociation activity and improving power density of solid oxide fuel cells (SOFC) at decreased temperature. Pt or Au dispersion in Pr1.90Ni0.71Cu0.21Ga0.05O4+d (PNCG) is prepared and the 3D tensile strain is successfully induced after sintering by a mismatch in thermal expansion coefficient. Due to higher hardness and melting temperature, Pt dispersion into bulk of PNCG introduces larger tensile strain than that by Au at the same amount. In particular, at 1 mol% Pt dispersion, large tensile strain of 0.67% is induced. Overpotential of 1 mol% Pt‐PNCG cathode is 8 times smaller (35 mV) than that of PNCG (270 mV) at 800 °C and 300 mA cm−2, and it is found that the cathodic overpotential of PNCG is decreased with tensile strain on both Pt and Au dispersion. This cathodic activity enhancement appears to be related with the increased diffusivity of oxide ion in PNCG. In this study, cathodic overpotential is more significantly influenced by the induced tensile strain comparing with the intrinsic catalytic activity of the dispersed metal. [ABSTRACT FROM AUTHOR]

Reduction in solid oxide fuel cells operating temperature to intermediate range (500–700°C) causes significant increase in the electrode polarization, especially at cathode due to high activation energy for oxygen reduction reaction (ORR). In fact, electrochemical performance of cathode significantly depends on the synthesis routes owing to the change in microstructures. PrBaCo2O5+δ double-perovskite cathode is synthesized using four different synthesis routes viz. combustion, sol–gel, mechanochemical alloying and solid-state reaction to obtain desired microstructure in view of optimum electrochemical performance. PrBaCo2O5+δ prepared with different routes crystalizes into tetragonal structure with crystallite size in the range of 48–64 nm. Maximum electronic conductivity (σdc = 178 S cm–1 at 700°C) and minimum polarization resistance (Rp = 0.112 Ω cm2 at 700°C) along with minimum Ea (0.51 eV) for combustion synthesized PrBaCo2O5+δ are attributed to its minimum effective particle size (382 nm), grain size and optimum porosity. Nanocrystallites not only improve sinterability and mechanical strength of cathode but also promotes (large, disordered surface area) chemical and electrochemical processes in it, thereby improve overall electrode performance. Defect equilibria are proposed to understand dependence of σdc and Rp on P O 2 , temperature and crystallite size. The electrochemical performance of PrBaCo2O5+δ shows that the charge transfer during ORR is the rate-limiting step. Thus, PrBaCo2O5+δ prepared using combustion can be a potential cathode for IT-OFC applications. [ABSTRACT FROM AUTHOR]

We report the development of a novel electrocatalyst composed of nanoarchitectured spinel cobalt manganese oxide and graphene for the oxygen reduction reaction (ORR). A combination of co-precipitation and hydrothermal methods achieved the unique nanoarchitecture of the electrocatalyst. The formation of CoMn2O4 electrocatalyst was confirmed by X-ray diffraction, transmission electron microscopy, and other spectroscopic and microscopic techniques. In addition to synthesizing CoxOy and MnxOy as control electrocatalysts, we created a physical mixture of CoMn2O4 and graphene to investigate the impact of their interface on electrocatalytic activity. Our findings indicate that CoMn2O4/graphene exhibits improved ORR activity, stability, and methanol tolerance in an alkaline medium. This enhancement can be attributed to the synergistic effect and strong interface interaction between CoMn2O4 and graphene. This study demonstrates the potential of the proposed electrocatalyst as a cost-effective and eco-friendly alternative for oxygen reduction in fuel cells applications. [ABSTRACT FROM AUTHOR]

The oxygen reduction reaction at the cathode is an essential process for protonic ceramic fuel cells. Composite cathode materials are commonly used towards the multiple requirements including high surface oxygen activity as well as sufficient electronic and ionic conductivities. In this study, a cobalt-free composite cathode composed of a perovskite La 0.6 Sr 0.4 FeO 3-δ phase and a Ruddlesden-Popper La 1.2 Sr 0.8 NiO 4+δ phase is synthesized with a self-assembly technology. The cathode process is mainly controlled by (I) the reduction of adsorbed oxygen atom to O− on the surface and (II) the migration of O− from the surface into the lattice. The former benefits from the high electrical conductivity of La 0.6 Sr 0.4 FeO 3-δ , and the latter is accelerated by La 1.2 Sr 0.8 NiO 4+δ attributed to its superior oxygen activity. The one-pot synthesized composite cathode shows an enhanced synergistic effect due to the uniform distribution of the two phases at the nanoscale. The cathode shows the lowest polarization resistances of 0.055 and 0.095 Ω cm2 at 700 °C in oxygen and air, respectively. The results show that self-assembled La 0.6 Sr 0.4 FeO 3-δ -La 1.2 Sr 0.8 NiO 4+δ nanocomposite is a promising cathode material for protonic ceramic fuel cells. [ABSTRACT FROM AUTHOR]

Chromium poisoning rapidly degrades the performance of solid oxide fuel cell (SOFC) cathode materials with superior oxygen reduction kinetics, such as La 0·6 Sr 0·4 Co 0·2 Fe 0·8 O 3 and La 0·6 Sr 0·4 CoO 3. Previously, LaNi 0.6 Fe 0.4 O 3 (LNF) demonstrated excellent resistance to chromium poisoning; however, it has relatively low electrocatalytic activity. Here, we investigate the effect of Zn substitution on the B-site of LNF cathode and deliver La(Ni 0·6 Fe 0.4) 1-x Zn x O 3-δ cathode materials with enhanced electrical and electrochemical properties. The ab initio first-principles calculations showed charged oxygen-vacancy defect formation energies of Zn-doped LNF (2.07 eV for La 8 Ni 5 Fe 2 Zn 1 O 24 and 1.83 eV for La 8 Ni 4 Fe 3 Zn 1 O 24) are lower than those of undoped LNF (2.92 eV for La 8 Ni 5 Fe 3 O 24). Various Zn-doped LNF materials are synthesized and tested for experimental validation of the DFT results. Electrical conductivity relaxation, temperature-programmed oxygen desorption, and electrochemical impedance spectroscopy analysis indicate enhanced oxygen reduction kinetics for LNFZ 3 (La(Ni 0·6 Fe 0.4) 0.97 Zn 0·03 O 3-δ). At 700 °C, LNFZ 3 has 25.4% less polarization resistance and 52.3% higher maximum power density of an anode-supported SOFC than LNF. Moreover, LNFZ 3 has the lowest polarization resistance compared with various studies reporting LNF cathode material. Furthermore, LNFZ 3 shows highly robust operation under accelerated chromium-poisoning conditions at 700 °C. The high performance and durability synergy makes the newly developed LNFZ 3 a promising cathode material for further commercial validation studies. [Display omitted] [ABSTRACT FROM AUTHOR]

One of the most popular solutions for electrochemical energy storage is metal–air batteries, which could be employed in electric vehicles or grid energy storage. Metal–air batteries have a higher theoretical energy density than lithium-ion batteries. The crucial components for the best performance of batteries are the air cathode electrocatalysts and corresponding electrolytes. Herein, we present several of the latest studies on electrocatalysts for air cathodes and bifunctional oxygen electrocatalysts for aqueous zinc–air and aluminium–air batteries. [ABSTRACT FROM AUTHOR]

Highly efficient and low‐cost Pt‐Co/CAB bimetallic cathode electrocatalysts were synthesized for hydrogen‐based proton exchange membrane fuel cell (PEMFC) using three different types of solvent, namely, dimethyl sulphoxide (DMSO), dimethylformamide (DMF), and ethylene glycol (EG). The physical characterization of synthesized cathode electrocatalysts Pt‐Co/CAB‐DMSO, Pt‐Co/CAB‐DMF and Pt‐Co/CAB‐EG was performed by scanning electron microscope–energy‐dispersive X‐ray (SEM–EDX), X‐ray diffraction (XRD), and transmission electron microscopy (TEM) techniques, whereas the electrochemical investigation of all three Pt‐Co/CAB electrocatalysts was performed by CV and EIS studies. The synthesized Pt‐Co/C‐EG electrocatalyst produced the highest power density of 19.61 mW/cm2 at a room temperature of 33°C. The power density increased to 26.11 mW/cm2, that is, 133%, when the cell operating temperature was raised from 33 to 70°C. The excellent performance of the Pt‐Co/CAB‐EG cathode electrode proves that it can be recommended as a commercial electrocatalyst for PEMFC cathode. In addition, the EG/EG was identified as the best solvent for the synthesis of Pt‐Co/CAB cathode electrocatalysts. [ABSTRACT FROM AUTHOR]

The correlation between lattice strain induced by metal dispersion into grain and the cathodic overpotential is studied for increasing oxygen‐dissociation activity and improving power density of solid oxide fuel cells (SOFC) at decreased temperature. Pt or Au dispersion in Pr1.90Ni0.71Cu0.21Ga0.05O4+d (PNCG) is prepared and the 3D tensile strain is successfully induced after sintering by a mismatch in thermal expansion coefficient. Due to higher hardness and melting temperature, Pt dispersion into bulk of PNCG introduces larger tensile strain than that by Au at the same amount. In particular, at 1 mol% Pt dispersion, large tensile strain of 0.67% is induced. Overpotential of 1 mol% Pt‐PNCG cathode is 8 times smaller (35 mV) than that of PNCG (270 mV) at 800 °C and 300 mA cm−2, and it is found that the cathodic overpotential of PNCG is decreased with tensile strain on both Pt and Au dispersion. This cathodic activity enhancement appears to be related with the increased diffusivity of oxide ion in PNCG. In this study, cathodic overpotential is more significantly influenced by the induced tensile strain comparing with the intrinsic catalytic activity of the dispersed metal.

Due to the synergistic affect between Pt, Ni SAs and Pt-Ni alloy NPs, the prepared PtNi SA-NPS -NDC catalyst delivered a superior Pt utilization efficiency. [Display omitted] • Dual single-atoms of Pt, Ni and PtNi alloy NPs supported on N -doped carbon was successfully prepared. • The catalyst exhibited impressive ORR catalytic activity in acidic medium. • The catalyst delivered a superior Pt utilization efficiency of 0.033g Pt kW−1 as cathode in PEMFC. • The main active sites of the designed catalyst for ORR was determined through DFT calculations. Pt-Ni (1 1 1) alloy nanoparticles (NPs) and atomically dispersed Pt have been shown to be the most effective catalysts for oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cells (PEMFCs) as well as less expensive compared to pure Pt NPs. To meet reaction kinetic demands and minimize the Pt utilization at cathode in PEMFCs, we propose a novel electrocatalyst composed of dual single-atoms (Pt, Ni) and Pt-Ni alloy NPs dispersed on the surface of N -doped carbon (NDC); collectively, PtNi SA-NPS -NDC. The optimized PtNi SA-NPS -NDC catalyst displays excellent mass activity and durability compared to commercial Pt/C. Electrocatalytic measurements show that the PtNi SA-NPS -NDC catalyst, with a metal loading of 4.5 wt%, exhibited distinguished ORR performance (E 1/2 = 0.912 V) through a 4-electron (4e-) pathway, which is higher than that of commercial 20 wt% Pt/C (E 1/2 = 0.857 V). The DFT simulations indicate Pt-Ni alloy NPs and PtNiN 2 C 4 atomic structure are the mobile active sites for ORR catalytic activity in PtNi SA-NPS -NDC. As a cathode catalyst in PEMFC, the Pt utilization efficiency in the PtNi SA-NPS -NDC catalyst is 0.033 g Pt kW−1, which is 5.6 times higher than that of commercial Pt/C (0.185g Pt kW−1). Therefore, the consumption of precious metals is effectively minimized. [ABSTRACT FROM AUTHOR]

Mixed ionic and electronic conduction (MIEC) in the composite cathode can alter oxygen stoichiometry and other physiochemical properties, eventually promoting the electrocatalytic functionalities for oxygen reduction reaction (ORR) at low operational temperatures (<650 °C). Here, we demonstrate a composite cathode of CoGd 0.8 Fe 1.80 O 4 /Gd 0.10 Ce 0.9 O 2−δ (CGFO-GDC), which delivers low electrode polarization resistance of 0.60 Ω cm2 at 550 °C. The best-performing sample CGFO-GDC exhbits the peak power density (PPD) of 611-343 mW cm−2 at 550-470 °C under a fuel cell conditions. Moreover, durability measurement verifies CGFO-GDC as a chemically stable cathode with improved ORR catalytic functionality. Additionally, first principle calculations using density function theory (DFT) were also conducted to analyze the ion diffusion mechanism of fabricated CGFO-GDC cathode. Our findings certify that introducing ionic conducting GDC into CGFO sample improves the catalytic functionalities. As a result, the composite CGFO-GDC based SOFC delivers minimum electrode polarization resistance with improved power output owing to its enhanced oxygen vacancies and fast catalytic reactions at 550 °C. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • We synthesized Au@PtNiAu concave octahedral core-shell nanocatalysts (Au@PtNiAu-COCS). • The mass activity of this catalyst is 11.22 times in ORR and 4.56 times in MOR than commercial Pt/C. • It exhibits a superior power density under fuel cell operation and better performance. • Its half-wave potential displacement after 30 k cycles is only 12 mV. • It retained the 78.8% of MA after 30 k cycles in ORR and lower CO oxidation overpotential in MOR. Despite the remarkable research efforts, the lack of ideal activity and state-of-the-art electrocatalysts remains a substantial challenge for the global application of fuel cell technology. Herein, is reported the synthesis of Au@PtNiAu concave octahedral core-shell nanocatalysts (Au@PtNiAu-COCS) via solvothermal synthesis modification and optimization approach. The special structure generating a large number of step atoms, enhancing the oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) activity and stability. The superior ORR mass activity of the Au@PtNiAu-COCS is 11.22 times than the exhibited of Pt/C initially by Pt loading, and 5.11 times by Pt + Au loading. After 30 k cycles the mass activity remains 78.8% (8.83 times the initial Pt/C activity) and the half-wave potential only shifts 12 mV. Au@PtNiAu-COCS has superior half-cell activity and gives ideal membrane electrode assemblies. Furthermore, for MOR the Au@PtNiAu-COCS show enhanced anti-toxic (tolerant) ability in CO. This work provides a new strategy to develop core-shell structure nanomaterials for electrocatalysis. [ABSTRACT FROM AUTHOR]

One big obstacle for the oxygen reduction reaction (ORR) electrode in solid oxide fuel cells (SOFCs) is the poor reaction activity and fast degradations caused by CO 2 poisoning. Here we report our design of an active A-site Ca-rich high-entropy Pr 0.1875 Ba 0.1875 Sr 0.1875 La 0.1875 Ca 0.25 CoO 3-δ (PBSLC 25 C) electrode, guided by the O p-band theory. When applied as a cathode in solid oxide fuel cells (SOFCs), it demonstrates high ORR activity and excellent CO 2 tolerance under realistic operating conditions. Ni-YSZ-based anode-supported cells with PBSLC 25 C cathodes demonstrate excellent peak power densities of 1.14 W cm−2, 1.04 W cm−2, and 0.77 W cm−2 in the air with 1%, 5%, and 10% CO 2 , respectively, at 750 °C. The engineered high-entropy PBSLC 25 C effectively diminishes the CO 2 poisoning effect and maintains active surfaces for fast oxygen exchange, as confirmed by the cell durability test in air containing CO 2 (5 and 10 vol%), Raman spectroscopy, and density functional theory calculations. [Display omitted] • A rational design of an A-site Ca-rich high-entropy perovskite electrode has been proposed. • The developed electrodes have demonstrated excellent activity and CO 2 tolerance. • The CO 2 tolerance mechanism has been confirmed via density functional theory calculations. [ABSTRACT FROM AUTHOR]

In this study, cost-effective cathode materials with high catalysis activity for oxygen reduction reaction (ORR) are proposed for use in intermediate-temperature solid oxide fuel cells. Cobalt-free Ba 0.5 A 0.5 Fe 0.8 Zr 0.2 O 3-δ (A=Sr2+/Sm3+, BSrFZ/BSmFZ) composites were synthesised using a smart self-assembled method that primarily utilised doped-BaZrO 3 and doped-BaFeO 3 cubic perovskites. The BSrFZ composite possesses a higher doped-BaFeO 3 (75 wt%) content, which facilitates the formation of oxygen vacancies and ORR catalysis. The BSmFZ composite exhibits a relatively higher content of doped-BaZrO 3 (31 wt%) than that of the BSrFZ composite, which is more suited to the electrolyte and improves the thermal expansion coefficient (16.0 × 10−6 K−1). Both composite cathodes exhibit nano- and micro-particles with extensive heterointerfaces and excellent cathode|electrolyte interfaces, which can assist the surface catalysis and oxygen species transport. The cell with a BSrFZ composite cathode achieved a higher maximum power density of 1.64 W cm−2 at 750 °C compared to that of the cell with a BSmFZ composite cathode that had a maximum power density of 0.99 W cm−2. The electrochemical analysis revealed that the BSrFZ composite cathode demonstrated enhanced oxygen adsorption dissociation and oxygen species reduction processes, which benefit from its enriched oxygen vacancies and high surface and heterointerface activities. [ABSTRACT FROM AUTHOR]

Using cheap graphite powder as catalyst and polytetrafluoroethylene (PTFE) as binder, graphite/PTFE composite coating cathodes were fabricated for efficient electrochemical synthesis of hydrogen peroxide (H2O2) in a no-diaphragm electrolysis system. A series of experiments were conducted to examine the influence of different factors, such as cathode thickness, cathode area, solution pH and current density, on H2O2 electrogeneration. Adjusting the thickness and area of the cathode was demonstrated to be effective in optimizing the electrocatalytic properties in oxygen reduction reaction. Among the cathodes investigated, the cathode with the thickness of 0.75 mm and area of 16 cm2 achieved the highest H2O2 accumulation and current efficiency. The H2O2 accumulation reached 207.5 mg L−1 and current efficiency reached 34.1% in 180 min when the current density is 5 mA cm−2 and the initial pH is 3.0. The present work successfully develops a simple approach to enhance the H2O2 electrogeneration, as well as the corresponding current efficiency, through optimization of cathode geometric parameters and operation conditions. [ABSTRACT FROM AUTHOR]

The manganese dioxide/graphene oxide (MnO2/GO) nanocomposites were prepared from hydrothermally synthesized MnO2 nanorods and graphene oxide. Electrocatalytic performance for the oxygen reduction reactions (ORR) of the fabricated MnO2/GO nanocomposites was evaluated using the rotating disk electrode (RDE) method. It is found that MnO2/GO nanocomposites deliver significantly enhanced performance compared to standalone MnO2 and GO with current density and onset potential values of 5.1 mA/cm2 and 0.93 V versus RHE, respectively. The alkaline membrane fuel cell (AMFC) characteristics were also studied. In particular, the single‐cell alkaline fuel cell stack with MnO2/GO nanocomposite as cathode loading produced a peak power density value of 82 mW/cm2. Our findings revealed great potential for MnO2/GO nanocomposites for their electrocatalytic performance and utilization in AMFC as the cathode. Namely, MnO2/GO achieved fuel cell functionalities that were comparable to the widely used commercial Pt/C. The enhanced electrochemical performance of MnO2/GO is attributed to the synergistic interaction between highly conductive GO sheets and active sites of MnO2 nanorods. The commendable performance of MnO2/GO suggests that it can be used as electrocatalysts in alkaline fuel cell applications. [ABSTRACT FROM AUTHOR]

Polyazomethine (PAM) prepared from the polycondensation between p-phenylene diamine (PDA) and p-terephthalaldehyde (PTAl) via Schiff reaction can physically crosslink (complex) with Co ions. Co-complexed PAM (Co-PAM) in the form of gel is calcined to become a Co, N-co-doped carbonaceous matrix (Co-N-C), acting as cathode catalyst of an anion exchange membrane fuel cell (AEMFC). The obtained Co-N-C catalyst demonstrates a single-atom structure with active Co centers seen under the high-resolution transmission electron microscopy (HRTEM). The Co-N-C catalysts are also characterized by XRD, SEM, TEM, XPS, BET, and Raman spectroscopy. The Co-N-C catalysts demonstrate oxygen reduction reaction (ORR) activity in the KOH(aq) by expressing an onset potential of 1.19–1.37 V vs. RHE, a half wave potential of 0.70–0.92 V, a Tafel slope of 61–89 mV/dec., and number of exchange electrons of 2.48–3.79. Significant ORR peaks appear in the current–voltage (CV) polarization curves for the Co-N-C catalysts that experience two-stage calcination higher than 900 °C, followed by double acid leaching (CoNC-1000A-900A). The reduction current of CoNC-1000A-900A is comparable to that of commercial Pt-implanted carbon (Pt/C), and the max power density of the single cell using CoNC-1000A-900A as cathode catalyst reaches 275 mW cm−2. [ABSTRACT FROM AUTHOR]

Subject to the binding strength between the cathode and the oxo-intermediates, the hydrogen peroxide (H 2 O 2) electrosynthesis with high productivity and high selectivity in oxygen reduction reaction (ORR) cannot be achieved simultaneously. In this work, the dual-metal-organic frameworks (NiFe-MOFs) is designed and synthesized, in which the e g orbital occupancy of Ni nodes is regulated by the super-exchange effect of Ni(2+σ)+-O-Fe(3-σ)+ bond. As a result, the binding strength between the cathode and the oxo-intermediates (*O 2 , *OOH) is optimized, which efficiently promotes oxygen reduction kinetics and inhibits O-O bond breakage. The H 2 O 2 yield of NiFe-MOFs cathode reaches 1.83 mol·g−1·h−1 with a Faraday efficiency of 96.3 % at 0.5 V vs. RHE, which is far superior to Ni-MOFs (0.21 mol·g−1·h−1, 65.4 %), Fe-MOFs (0.65 mol·g−1·h−1, 57.5 %). This work offers a new strategy to design and develop cathodic catalysts for H 2 O 2 electrosynthesis with high productivity and high selectivity. [Display omitted] • H 2 O 2 synthesis with high yield and selectivity is achieved on NiFe-MOFs cathode. • The super-exchange effect of Ni-O-Fe regulates the e g orbital occupancy of Ni node. • The binding strength with oxo-intermediates is optimized to enhance 2e- ORR. [ABSTRACT FROM AUTHOR]

As one of the most promising methods for H2O2 production, H2O2 electroproduction has received increasingly more attention. In this study, a spherical particle polydopamine (pDA) modified carbon felt (noted as ht-pDA/ACF) for H2O2 production was fabricated. At a constant potential of 2.0 V and pH of 1.0, the H2O2 production of the ht-pDA/ACF cathode reached 220 mg/L after 6 h of electrolyzing, compared to the 30 mg/L H2O2 production of raw carbon felt. Firstly, the spherical pDA exposes more active sites that are favorable to the 2e− ORR compared to pDA film. Secondly, the ring cleavage and re-cyclization of indole structure in the pDA during electrolyzing could form the radicals that act as the intermediate to the H2O2 formation. This research exhibits a low-cost method to modify carbon materials for effective H2O2 electroproduction. The ht-pDA/ACF cathode is promising for green H2O2 production and wastewater treatment. [ABSTRACT FROM AUTHOR]

Exhibiting a very high surface area, a good electrical conductivity and a high density of active sites, nitrogen-doped graphenic materials are considered as promising catalysts for the oxygen reduction reaction (ORR). Seldom studied in acidic media, N-doped graphenic foams were tested here as the cathode catalysts of a polymer electrolyte membrane fuel cell (PEMFC). The materials were prepared via a solvothermal-based process, by reacting either cyclohexanol and ethanolamine or 1-(2-hydroxyethylethyl) piperidine with metallic sodium, under high pressure and temperature. Membrane electrode assemblies were prepared with a Pt/C anode, 212 Nafion membrane, and an 8 mm disk cathode based on the graphenic materials. The performance exhibited by the PEMFC was evaluated using chronopotentiometry and impedance spectroscopy, depending on the synthesis conditions. The kinetic parameters of the ORR were estimated by interpretation of the experimental data: the high Tafel slope found might express the partial control of oxygen diffusion through the graphenic microporous structure. Relationships between the electrochemical behavior of the materials and their structural properties are discussed. Moderately crystallized materials with a low oxygen content showed the highest catalytic properties, with a current density larger than 30 mA cm−2 and a maximum power density at 2.3 mW cm−2. [ABSTRACT FROM AUTHOR]

Platinum (Pt) and Samaria-doped ceria (SDC) as cermet cathodes were investigated to enhance oxygen reduction reaction (ORR) kinetics in low-temperature solid oxide fuel cells (SOFCs). Pt is widely known for its high catalytic activity, whereas SDC is one of the most promising oxide ionic conductors as an LT-SOFC electrolyte. To improve both the catalytic activity and oxygen ionic transportation, a co-sputtering technique was used to fabricate a composite cathode by adjusting the elemental composition of Pt and SDC. This technique demonstrated that the Pt-SDC cermet cathode can increase the electrochemical reaction sites and offer a percolated pathway for rapid electron-ion conduction within the cermet structure. The electrochemical analysis results also revealed that the fuel cells coated with Pt-SDC cermet cathodes outperformed the pure Pt-coated fuel cells in terms of peak power density. The electrochemical impedance spectroscopy analysis indicated that the improved ORR kinetics of Pt-SDC cermet cathodes were the main reason for the improved fuel cell performance by catalyzing both electron and oxygen ion conduction. • Pt-SDC cermet cathodes were fabricated via co-sputtering technique for LT-SOFCs. • The chemical composition of cermet cathodes was controlled by RF power of SDC. • The TPB density can be enlarged by mixing the both Pt and SDC with co-sputtering. • Optimized ratio of Pt and SDC can provide the percolating path for charge transport. • Pt-SDC cermet cathode can increase the performance of fuel cell by catalyzing ORR. [ABSTRACT FROM AUTHOR]

A key obstacle to commercialization of solid oxide fuel cells is the sluggish oxygen reduction on the cathodes. In this work, a series of calcium-doped La 0.5- x Ca x Ba 0.5 FeO 3-δ (x = 0–0.2) are developed as highly active cathode materials and systematically evaluated their physicochemical properties. Among all the components, the La 0.35 Ca 0.15 Ba 0.5 FeO 3-δ cathode delivers the minimal polarization resistance (0.059 Ω cm2) and maximum power densities (452 mW cm−2) at 800 °C, and possesses better stability after long-term operation. Based on the analysis results of electrochemical impedance spectra and distribution of relaxation time, the adsorption process of oxygen on the La 0.35 Ca 0.15 Ba 0.5 FeO 3-δ cathode surface is proved to be the major rate-limiting step. These results suggest that La 0.35 Ca 0.15 Ba 0.5 FeO 3-δ can be used as a candidate cathode material for solid oxide fuel cells. • Ca-doped La 0.5−x Ca x Ba 0.5 FeO 3-δ powders are synthesized and characterized. • The La 0.35 Ca 0.15 Ba 0.5 FeO 3-δ cathode shows excellent ORR catalytic activity. • The lowest R p of 0.059 Ω cm2 is achieved at 800 °C. [ABSTRACT FROM AUTHOR]

On-site H 2 O 2 electrosynthesis via two-electron oxygen reduction reaction (ORR) is attracting great interest for water treatment. The use of carbon black-based gas-diffusion electrodes (GDEs) is especially appealing, but their activity, selectivity and long-term stability must be improved. Here, a facile GDEs modification strategy using trace polymethylhydrosiloxane (PMHS) allowed reaching a outstanding H 2 O 2 production, outperforming the conventional polytetrafluoroethylene (PTFE)-GDE (1874.8 vs 1087.4 mg L−1 at 360 min). The superhydrophobicity conferred by PMHS endowed the catalytic layer with high faradaic efficiencies (76.2%−89.7%) during long-term operation for 60 h. The electrochemical tests confirmed the high activity and selectivity of the PMHS-modified GDE. Moreover, the efficient degradation of several micropollutants by the electro-Fenton process demonstrated the great potential of the new GDE. An in-depth understanding of the roles of PMHS functional groups is provided from DFT calculations: the −CH 3 groups contribute to form a superhydrophobic interface, whereas Si-H and as-formed Si-O-C sites modulate the coordination environment of active carbon centers. [Display omitted] • Boosted H 2 O 2 activity and selectivity of siloxane-modified gas-diffusion electrode (GDE). • H 2 O 2 production: 1874.8 vs 1087.4 mg L−1 with PTFE/PMHS-GDE and PTFE-GDE. • Superhydrophobicity of PTFE/PMHS-GDE keeps durable high current efficiency (> 76%). • Enhanced removal of 8 organic micropollutants by EF process using the new GDE. • DFT study to correlate the role of PMHS groups with the improved electrocatalysis. [ABSTRACT FROM AUTHOR]

In this study, a novel magnetic nanocomposite of Ru@Fe 3 O 4 /rGO was successfully synthesized by a simple hydro-thermal method. The Ru@Fe 3 O 4 /rGO particles were assembled and immobilized for innovative magnetically assembled electrode (MAE) without any binder, and the electrode was further applied in heterogeneous electro-Fenton (hetero-EF) process for the degradation of diclofenac (DCF). The results showed that rGO could remarkably enhance the conductivity and catalyze the two-electron oxygen reduction, which greatly improved the generation of H 2 O 2. In addition, the mixture valence of Fe and Ru species might provide rich reaction sites and enhance electron transfer by synergy. Thus, the Ru@Fe 3 O 4 /rGO MAE exhibited a stable and high electrocatalytic activity in the hetero-EF process for DCF degradation over a wide pH range from 2 to 9 owing to the higher electroactive surface area (EASA) and lower charge/mass-transfer resistance. The DCF degradation efficiency could reach about 100% within 90 min under pH 5 and current 40 mA, and the Ru@Fe 3 O 4 /rGO MAE showed high stability and reusability after five cycles. Theoretically, 1O 2 and •OH were the main reactive oxygen species (ROS) participating in DCF degradation in the Ru@Fe 3 O 4 /rGO MAE hetero-EF process. Furthermore, according to the LC-MS/MS intermediates, the possible DCF degradation pathway was deduced including dechlorination, hydroxylation and ring opening attacked by ROS. Eleven intermediates were detected during DCF degradation in the MAE hetero-EF process, and the ecological risk of DCF degradation in Ru@Fe 3 O 4 /rGO MAE hetero-EF process was significantly reduced. This study provides new insights into the magnetically assembled electrode of Ru@Fe 3 O 4 /rGO and displays a new practical application prospect of the materials for high-efficient removal and degradation of DCF from wastewater. [Display omitted] • The innovative magnetically assembled electrode (MAE) was used in hetero-EF process. • Nearly 100% of DCF were degraded by Ru@Fe 3 O 4 /rGO MAE at current 40 mA within 90 min. • Ru@Fe 3 O 4 /rGO MAE showed high activity and stability in hetero-EF process for DCF degradation under pH 2–5. • 1O 2 and.•OH were the main ROS participating in DCF degradation in Ru@Fe 3 O 4 /rGO MAE hetero-EF process. [ABSTRACT FROM AUTHOR]

Layered perovskite (La1−xSrx)2CoO4±δ (x = 0.3, 0.4, 0.5) oxides were prepared using sol–gel route and evaluated as the cathode materials for intermediate-temperature solid-oxide fuel cells. (La1−xSrx)2CoO4±δ has a tetragonal structure with space group of I4/mmm in all cases of x levels. The average thermal expansion coefficient of (La1−xSrx)2CoO4±δ is relatively low and slightly increases with x, which can be ascribed to the sway of Sr doping on the spin-state transition of Co ions. X-ray photoelectron spectroscopy and thermogravimetric analysis show that Co ions exist in mixed oxidation states, but the lattice oxygen content considerably varies with x. Regarding transport property, (La1−xSrx)2CoO4±δ behaves like a semiconductor in the temperature range of 200–800 °C, and the electrical conductivity significantly increases with x. As one of the most important results, electrochemical performance of (La1−xSrx)2CoO4±δ cathode is affected by x in a complex manner, and x = 0.4 cathode, i.e., La1.2Sr0.8CoO4±δ, has the most favored area-specific resistance of 0.062 Ω cm2 and the highest power density of 630 mW cm−2 in an electrolyte-supported single cell at 800 °C, showing a rapid kinetics toward oxygen reduction reaction. This study demonstrates that the structural, transport, thermal, and electrochemical properties of (La1−xSrx)2CoO4±δ cathodes significantly depend on the La/Sr ratio at the A-site of lattice. Rietveld refinement profile and temperature-dependent electrochemical performance for La1.2Sr0.8CoO4±δ cathode material [ABSTRACT FROM AUTHOR]

In this study, LSM-YSZ composite cathodes were analyzed by changing the firing temperature, composition, and operating temperature to determine the contribution of each step of the oxygen reduction reaction (ORR). The overall resistance of the cathode reaction was characterized by fitting the AC impedance spectra with an equivalent circuit model. It was found that initial reactions of ORR (dissociative adsorption) are the main rate-determining step (RDS) regardless of operating or sintering temperature, while reactions on LSM surface become the main RDS when the ratio of LSM catalysts has a relatively small proportion. The [LSM-YSZ] 5:5 cathode fired at 1100 °C showed the best microstructure and lowest resistance in the ORR at an operating temperature of 700 °C (R HF : 0.18 Ωcm2, R MF : 0.20 Ω cm2, R LF : 0.25 Ωcm2, R cathode : 1.14 Ωcm2). This demonstrates the potential use of LSM-YSZ cathodes for IT/LT-SOFC without the use of expensive materials, such as LSCF and BSCF. [ABSTRACT FROM AUTHOR]

Developing MIEC materials with high electrocatalytic performance for the ORR and good thermal/chemical/structural stability is of paramount importance to the success of solid oxide fuel cells (SOFCs). In this work, high-activity Bi 0.5 Sr 0.5 FeO 3- δ - x Ce 0.9 Gd 0.1 O 1.95 (BSFO- x GDC, x = 10, 20, 30 and 40 wt%) oxygen electrodes are synthesized, and confirmed by XRD, SEM and EIS, respectively. The crystal structure, microstructure, electrochemical property and performance stability of the promising BSFO- x GDC composite cathodes are systematically evaluated. It is found that introducing GDC nanoparticles can obviously improve the electrochemical property of the porous composite electrode. Among all these composite cathodes, BSFO-30GDC composite cathode shows the best ORR activity. The peak power density of anode supported single cells employing BSFO-30GDC composite cathode reaches 709 mW cm−2 and the electrode polarization resistance (R p) of the BSFO-30GDC is about 0.14 Ω cm2 at 700 °C. The analysis of the oxygen reduction kinetic indicates that the major electrochemical process of the GDC-decorated composite cathode is oxygen adsorption-dissociation. These preliminary results demonstrated that BSFO-30GDC is a prospective composite cathode catalyst for SOFCs because of its outstanding ORR activity. [ABSTRACT FROM AUTHOR]

One of the most important factors to commercialized yttria-stabilized zirconia (YSZ)-based solid oxide fuel cell (SOFC) is a highly active mixed-conducting cathode at reduced temperatures. Herein, we propose a new strategy of fluorine anion (F−) doping to enhance electrochemical performance of the H+/O2−/e triple-conducting BaCo 0.4 Fe 0.4 Zr 0.1 Y 0.1 O 3-δ (BCFZY) perovskite cathode for YSZ-based SOFCs. The F−-doped BCFZY as BaCo 0.4 Fe 0.4 Zr 0.1 Y 0.1 O 2.95-δ F 0.05 (BCFZYF) retained the cubic structure with better symmetry. The doping of minor fluorine in oxygen-site was found to increase the oxygen exchange capability and thus oxygen reduction reaction (ORR) catalytical activity, as reflected by lower area specific resistance (ASR) of cathode on symmetrical cells. Maximum power density of 786 mWcm−2 was achieved at 800 °C for anode-supported single cell with BCFZYF cathode, being 1.7 times higher than that with BCFZY cathode. Furthermore, the single cell with BCFZYF cathode demonstrated excellent stability without any degradation of current density over 200 h at 700 °C. The present work clarifies that the fluorine doping strategy is highly effective to promote the ORR activity of the triple-conducting BCFZY cathode for state-of-the-art oxygen-conducting SOFC. • Fluorine anion doping is proposed for triple-conducting BaCo 0.4 Fe 0.4 Zr 0.1 Y 0.1 O 3-δ (BCFZY) perovskite cathode. • F−-doped BCFZY shows highly promoted cathodic performance. • Single cell with F−-doped BCFZY cathode and YSZ electrolyte exhibits outstanding output performance. • F−-doped BCFZY cathode demonstrated excellent long-term stability. [ABSTRACT FROM AUTHOR]

Self-assembly is an emerging strategy for preparing composite cathodes with good oxygen electrochemical reduction activity and congenital chemical compatibility for intermediate-temperature solid oxide fuel cell (IT-SOFC). Here we report that a self-assembled BaCo 0.6 Zr 0.4 O 3-δ (BZC-BC) nanocomposite is prepared through one-pot glycine-nitrate process and exhibits high cathode performance. The BZC-BC nanocomposite is composed of 62 mol% cubic perovskite BaZr 0.82 Co 0.18 O 3-δ (BZC) as an ionic conductor and 38 mol% hexagonal perovskite BaCo 0.96 Zr 0.04 O 2.6+δ (12H-BC) as a mixed ionic and electronic conductor. The BZC-BC nanocomposite has the pomegranate-like particles aggregated with a larger number of nanoparticles (50-100 nm) which greatly enlarge the three-phase boundary sites. The BZC-BC nanocomposite exhibits a thermal expansion coefficient of 12.89 × 10−6 K−1 well-matched with that of Ce 0.8 Gd 0.2 O 3-δ (12.84 × 10−6 K−1) electrolyte. The high electro-catalytic activity of BZC-BC nanocomposite cathode for oxygen reduction is reflected by the low polarization resistances of oxygen ions incorporation at cathode/electrolyte interface (0.02823 Ω cm2), oxygen species diffusion (0.03702 Ω cm2) and oxygen adsorptive dissociation (0.07609 Ω cm2) at 700 °C. The single cell with BZC-BC nanocomposite cathode achieves the maximum power density of 1094 mW cm−2 at 650 °C and shows good stability under 25 h run. [ABSTRACT FROM AUTHOR]

• Auricularia is used to prepare Co 8 FeS 8 /NSC via thorough coordination of precursors. • MFC with Co 8 FeS 8 /NSC (900 °C) cathode has higher performance and stability than Pt/C. • Co2+ and Fe2+ in Co 8 FeS 8 provide more active sites to achieve rapid kinetics for ORR. • Co 8 FeS 8 with multiple atoms boosts side-on oxygen adsorption to enhance ORR activity. • Porous structure with N-species has abundant available channels for mass transfer. The main issues regarding the practical application of microbial fuel cells (MFCs) are the poor activity and tolerance of oxygen reduction reaction (ORR) catalysts in wastewater. In this study, Auricularia chelated with Co, Fe and S ions is used as a nitrogen (N)-enriched carbon source to prepare N-doped bimetallic sulfide (Co 8 FeS 8)-embedded carbon spheres (Co 8 FeS 8 /NSC) using a hydrothermal method. The effects of various temperatures (800–950 °C) on the structure and catalytic activity of Co 8 FeS 8 /NSC catalysts are investigated. The MFC with a Co 8 FeS 8 /NSC (900 °C) cathode obtained the maximum power density of 1.002 W m−2, which is higher than that of Pt/C (0.88 W m−2). After 1440 h of operation, the power density of the Co 8 FeS 8 /NSC (900 °C) cathode only declined by 5.49%, indicating that the Co 8 FeS 8 activity, charge transfer and O 2 transport were slightly influenced by the attached microbes and poisonous substances in the wastewater. The electrochemical results indicate that Co 8 FeS 8 /NSC (900 °C) mainly proceeds by a 4e− ORR pathway, indicating that Co 8 FeS 8 (Co2+ and Fe2+) wrapped in NSCs (carbon spheres) can trigger synergistic effects to provide more active sites and high electrical conductivity to achieve the rapid kinetics required for the ORR. Moreover, the porous structures of the NSCs (220.97 m2 g−1) with incorporated pyridinic N, pyrrolic N and graphitic N can provide abundant available channels for O 2 and OH− transport to ensure the preferential accessibility of the reactant molecules to active sites. This indicates that Auricularia-derived Co 8 FeS 8 /NSC catalysts have great potential as alternatives for precious metal-based catalysts in neutral electrolyte MFCs. [ABSTRACT FROM AUTHOR]

The cathode is a critical component in the utilization of solid oxide fuel cells (SOFCs) technique. Herein, the perovskite oxide SmBa 0.5 Ca 0.5 CoCuO 5+δ (SBCCC) with exsolved CaCuO 2 -type phase was proposed as an advanced cathode material of SOFCs. It is synthesized through a simple sol-gel method and displays a good chemical and thermal matching with Gd 0.1 Ce 0.9 O 1.95 electrolyte, high electrocatalytic activity and durability to the oxygen reduction reaction. Its thermal expansion coefficient is 14.3 × 10−6 °C−1, which is very close to that of Gd 0.1 Ce 0.9 O 1.95 electrolyte (11.5 × 10−6 °C−1). The area-specific resistance low to 0.076 Ω cm2 (700 °C) and output power density high to 1.23 W cm−2 (800 °C) were obtained for the SBCCC-based symmetrical and single cells. A stable and non-attenuating output current density was acquired for the SBCCC-based single-cell working at 750 °C and 0.7 V for 200 h. These results demonstrate that SBCCC with exsolved CaCuO 2 -type phase is an attractive electrocatalyst for SOFC application. • An advanced cathode material with exsolved second phase is proposed. • Its average thermal expansion coefficient is 14.3 × 10−6 °C−1. • Its ASR is 0.076 Ω cm2 at 700 °C and PPD is 1.23 W cm−2 at 800 °C. • No performance degeneration was observed for the SOFC working at 750 °C for 200 h. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) flower-like Bi 2 SiO 5 nanomaterials (FLB) and 3D flower-like Bi 2 SiO 5 @nitrogen doped graphene nanomaterials (FLBNG) have been originally synthesized. Notably, as-synthesized FLB and FLBNG nanomaterials have not yet been discussed in previous reports. The FLBNG nanomaterials have been for the first time studied as the cathodic catalysts for Fuel cell. Research results have shown that the FLBNG-2 possesses perfectly 3D flower-like Bi 2 SiO 5 with numerous uniformly coiled nanowires and exhibits good methanol immunity, high activity and high durability during oxygen reduction reaction (ORR) process under acidic and basic electrolytes. The value of onset potential (E 0) for FLBNG-2 in alkaline electrolyte can reach to 1.091 V, Tafel slope of FLBNG-2 is 45.637 mV dec−1 and its limiting current density (J L) is 6.49 mA cm−2. Similarly, These ORR performances in acidic electrolyte are also better than those of 20 wt% commercial Pt/C and most of the associated reports. Thus, the FLBNG-2 could be a potential ORR catalyst, applied in the cathode of fuel cells to enhance the kinetic rate, decrease costs and enhance durability. And this synthesis method may be provide a good design to synthesize other 3D flower-like nanomaterials with desirable properties. [ABSTRACT FROM AUTHOR]

One of the significant motivations in developing intermediate-temperature solid oxide fuel cells (IT-SOFCs) is to design cobalt-free cathodes with high electrocatalytic activity and CO 2 tolerance ability. In this work, iron-based perovskite materials Bi 0.5 Sr 0.5 Fe 1- x Ta x O 3- δ are investigated as potential cathodes for IT-SOFCs. The effects of Ta doping on crystal structure, thermal expansion coefficients and electrocatalytic activities are systematically evaluated. Among the Ta-doped oxides, Bi 0.5 Sr 0.5 Fe 0.9 Ta 0.1 O 3- δ exhibits the highest electrochemical performance with the lowest polarization resistance (R p) of 0.124 Ω cm2 at 700 °C in air. The peak power density of the single cell with Bi 0.5 Sr 0.5 Fe 0.9 Ta 0.1 O 3- δ cathode reaches 1.36 W cm−2 at 700 °C. Compared to Bi 0.5 Sr 0.5 FeO 3- δ , the improved CO 2 tolerance of Ta-doped oxides can be attributed to the high acidity of Ta5+ cations and the increased average metal bond energy (ABE) within the material. Further study proves that the adsorption-dissociation process of molecular oxygen is the limiting step for oxygen reduction reaction (ORR) on Bi 0.5 Sr 0.5 Fe 0.9 Ta 0.1 O 3- δ cathode. [ABSTRACT FROM AUTHOR]

Although La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 (LSCF) owns a high level of maturity as a cathode material for intermediate and high-temperature SOFCs, there still exists tremendous potential for it to be employed under an efficient low-temperature working conditions. Since the charge transfer and oxygen ions diffusion act as pivotal obstacles to realizing the operation of LT-SOFCs (below 600 °C), the B-site doping elements (Ni, Cu, Nb) in commercial LSCF are selected using the first-principles calculation. Based on the theoretical findings, the novel Cu-doped La 0.6 Sr 0.4 Co 0.2 Fe 0.8-x Cu x O 3 (LSCFCx, x = 0, 0.1, 0.2) cathode materials are synthesized with exploring the phase structure, valence states of the elements, and thermogravimetric properties. Among different doping elements, Cu doping could facilitate the electrochemical performance of LSCFCx cathode by the enhancement of electrons at B-site and enrichment the of oxygen vacancies. Arising from the inspiring charge transfer and the accelerating oxygen ion transportation, Cu-substitution yields superior activity than other LSCF doping elements. The polarization resistant and activation energy values for LSCFC0.2 cathode attenuates more than 71% and 35% in contrast to the undoped LSCF cathode, respectively. The maximal power density of the anode-supported single cells utilizing LSCFC0.2 cathode outputs 0.594 W ∙ cm‐2 at 600 °C and promotes over 41% than commercial LSCF at the same condition. These results conclusively point to a practical Cu-doping strategy for the development of highly efficient cathodes for LT-SOFCs. Cu doping in LSCF displays the lowest state density for oxygen bonding, the highest Bader charge in B-site metals and the smallest oxygen vacancy formation energy among other metal-doping based on first-principles DFT, then novel Cu-doped LSCF perovskite cathodes for LT-SOFCs are synthesized and evaluated. The LSCFC0.2 cathode can promote the electrochemical performance by reinforcing charge transfer and accelerating the oxygen transportation. [Display omitted] • Charge transfer is significantly promoted by Cu addition in LSCF based on DFT results. • Cu substitution in LSCF presents the lowest generation energy of oxygen vacancy. • Cu introduction reduces B-site valence and generates more oxygen vacancy as expected. • The prepared LSCFC0.2 cathodes displays significant drops of R p & E a than LSCF. • The peak power density of LSCFC0.2 notably outputs over 41% than commercial LSCF. [ABSTRACT FROM AUTHOR]

To attain superior electrochemical performance, a new series of high-entropy double perovskites are investigated as cathodes for solid oxide fuel cells. In this study, three PrBa 0.5 Sr 0.5 Co 1.5 Fe 0.5 O 5 double perovskites with different dopings of La, Pr, Sm, Gd, Nd, Y elements in A-site, high-entropy oxides (HEOs) cathodes are successfully prepared by EDTA-citrate combustion method and used as potential cathodes for SOFC at intermediate temperature. Three HEOs cathodes all form single phase double perovskite structure and match chemically well with Gd 0.2 Ce 0.8 O 2-δ (GDC) electrolyte. Linear thermal expansion coefficient of (La 0.2 Pr 0.2 Sm 0.2 Gd 0.2 Nd 0.2)Ba 0.5 Sr 0.5 Co 1.5 Fe 0.5 O 5 (LPSGNBSCF) at 200–1000 °C range is found to be moderate, 18.39 × 10−6 K−1. Typical anode supported SOFC with LPSGNBSCF cathode exhibits an excellent output performance of 1000 mW cm−2 with a lower polarization resistance of 0.3 Ω cm2 at 800 °C. These results might suggest that LPSGNBSCF can be a potential excellent cathode for SOFC. • High entropy PrBa 0.5 Sr 0.5 Co 1.5 Fe 0.5 O 5+δ cathodes with A-site dopings are prepared. • SOFC with LPSFNBSCF cathode exhibits output performance of 1000 mW cm−2 at 800 °C. • LPSGNBSCF can be a potential cathode for SOFC. [ABSTRACT FROM AUTHOR]