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A highly active mixed conductive cathode is required for solid oxide fuel cells (SOFCs) based on yttria-stabilized zirconia (YSZ) at reduced temperatures, which is one of the most important factors for their commercialization. Herein, we propose a Na+ doping strategy to activate and stabilize the triple-conducting (H+/O2−/e−) layered perovskite oxide of representative NdBa 0.5 Sr 0.5 Co 1.5 Fe 0.5 O 5+δ (NBSCF) for high-performance YSZ fuel cells. The results show that Na+ doping enhances the electrochemical properties of the NBSCF cathode, with polarization impedance decreasing from 0.105 to 0.080 Ω cm2 at 750 °C and output power increasing from 946.05 to 1435.75 mW cm−2 at 800 °C. Furthermore, high-temperature XRD (HT-XRD) and the oxygen temperature-programmed desorption (O 2 -TPD) further confirm that Na+ doping can improve the structural stability of NBSCF. The single cell with a Na-doped NBSCF cathode showed no degradation of current density for more than 120 h at 700 °C and exhibited good stability. This work demonstrates the promise of Na+ doping for layered perovskite cathodes and an effective way to promote fuel cell performance. [ABSTRACT FROM AUTHOR]

Graphite nitrogen, pyridine nitrogen and pyrrole nitrogen are the main nitrogen types in nitrogen-doped graphene materials. In order to investigate the mechanism of the oxygen reduction activity of nitrogen-doped graphene, several models of nitrogen-doped graphene with different nitrogen contents and different nitrogen types are developed. The nitrogen content is varied from 1.3 at% to 7.8 at%, and the adsorption energy is calculated according to the established models, then the band gaps are analyzed through the optimization results, so as to compare the magnitude of the conductivity. Finally, the oxygen reduction activity of graphite nitrogen-doped graphene (GNG) is found to be better than pyridine nitrogen-doped graphene (PDNG) and pyrrole nitrogen-doped graphene (PLNG) when the nitrogen content is lower than 2.6 at%, and the oxygen reduction activity of PDNG is the best when the nitrogen content was higher than 2.6 at%.

Abstract Oxygen electrocatalysis is crucial for renewable energy conversion and storage technologies. Specifically for proton exchange membrane fuel cells (PEMFCs), oxygen reduction reaction (ORR) is the primary reaction that determines performance and costs. The ORR activity and durability are commonly assessed using a rotating disk electrode (RDE). However, there are numerous inconsistencies in the RDE measurements among researchers when comparing newly developed ORR catalysts to state‐of‐the‐art ones. These inconsistencies in activity and durability evaluation and deviations from standard protocols result in irreproducible screening and benchmarking of electrocatalysts. Despite the fact that the US Department of Energy has established and regularly revises the standard protocols, many reported studies do not adhere to these guidelines. This perspective aims to draw attention to the discrepancies in ORR activity and stability measurements at RDE as primary screening and emphasizes implementing the mandatory standard for a meaningful comparison of ORR activity and durability. We intend to emphasize the use of available ORR test standards ubiquitously for more accurate comparisons and accelerate the development of fuel cell catalysts.

A new type of Ruddlesden-Popper Pr 1.2 Sr 0.8 Ni 1−x Mo x O 4+δ (PSNMO) cathode with x = 0, 0.025, 0.050, 0.075 was prepared by the sol-gel method. The conductivity of Pr 1.2 Sr 0.8 NiO 4+δ cathodes reaches the max values and then decreases the continuous increase of Mo amount in all the Mo doped cathodes. Results of electrochemical impedance spectroscopy show that the Pr 1.2 Sr 0.8 Ni 0.950 Mo 0.050 O 4+δ has the lowest polarization resistance of 0.110 Ω cm2 at 750 °C among PSNMO cathodes. And results of electrical conductivity relaxation and X-ray photoelectron spectroscopy indicate that Mo-doping improves the oxygen surface exchange properties of PSNMO cathodes, which can be mainly ascribed to co-interaction of oxygen vacancy and interstitial oxygen in PSNO cathodes after Mo-doping. • Mo-doping improves the electrochemical performance of Pr 1.2 Sr 0.8 NiO 4+δ cathodes. • The improvement mechanism of Pr 1.2 Sr 0.8 NiO 4+δ cathodes is revealed by Mo-doping. • Oxygen surface exchange properties of Pr 1.2 Sr 0.8 NiO 4+δ cathodes are greatly improved by Mo-doping. [ABSTRACT FROM AUTHOR]

This work demonstrates a nanoscale zirconia layer coated by atomic layer deposition (ALD) with only a few coating cycles on a nano-porous platinum cathode surface to serve as a physical confinement to prevent the electrode agglomeration under high temperature operation, and at the same time to enhance the cathode oxygen reduction activity. The resulted enhancement in cathode electrochemical performance can arise from the discontinuous ZrO 2 film that facilitates the oxygen adsorption on cathode surface and decreases the oxygen adsorption–desorption resistance. [ABSTRACT FROM AUTHOR]

In this study, Pt-Pd alloy catalyst was fabricated on carbon papers via electro-deposition as an alternative catalyst for oxygen reduction in air-cathode Microbial Fuel Cells (MFCs). Effects of electro-deposition cycles and supporting materials (graphene and carbon nanotubes (CNTs)) on oxygen reduction reaction (ORR) activity of the Pt-Pd electrode and power generation in MFCs were investigated. The structural and electrochemical properties of the Pt-Pd catalyst were characterized by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). Results showed that the Pt-Pd electrode showed a good ORR activity. A MFC with a Pt-Pd cathode of 15 deposition cycles produced a maximum power density of 1274 mWm −2 , comparable to that with a conventional Pt/C cathode (0.5 mg Pt cm −2 ). CNT as the supporting material further increased ORR activity of the Pt-Pd electrode and power generation capacity in MFCs, while graphene as the supporting material did not produce positive effects. XRD results confirmed the presence of Pt/Pd elements on the electrode. SEM results showed that decoration using CNT reduced Pt-Pd particle size and promoted them even dispersion on the carbon paper. The Pt-Pd electrode attained a comparable performance to the Pt/C electrode when controlling an optimum deposition cycles and using CNT as the supporting materials, which demonstrates the potential of replacing Pt as an oxygen reduction catalyst in MFCs due to high oxygen reduction activity and relatively low cost. [ABSTRACT FROM AUTHOR]

Solid oxide fuel cells with nano-sized Co 1.5 Mn 1.5 O 4 (CMO) crystals infiltrated LSM-YSZ cathodes have been investigated using XRD, SEM, EIS and cell performance measurements. 20∼30 nm nanocrystals of Co 1.5 Mn 1.5 O 4 are present on the surfaces of LSM and YSZ particles. The infiltrated cells display more than 2 times higher power density than the non-infiltrated cell under 0.7 V at the same temperature in 600–700 °C. The Co 1.5 Mn 1.5 O 4 infiltration reduces both ohmic resistance and polarization resistance in the cells. The distribution of relaxation times (DRT) analysis of the EIS data depicts that oxygen reduction process is greatly accelerated on the infiltrated cathode, which is attributed to high catalytic activity of nano-sized CMO crystals. [ABSTRACT FROM AUTHOR]

Abstract: Carbon-based films with nitrogen species on their surface were prepared on a glassy carbon (GC) substrate for application as a non-platinum cathode catalyst for polymer electrolyte fuel cells. Cobalt and carbon were deposited in the presence of N2 gas using a pulsed laser deposition method and then the metal Co was removed by HCl-washing treatment. Oxygen reduction reaction (ORR) activity was electrochemically determined using a rotating disk electrode system in which the film samples on the GC substrate were replaceable. The ORR activity increased with the temperature of the GC substrate during deposition. A carbon-based film prepared at 600°C in the presence of N2 at 66.7Pa showed the highest ORR activity among the tested samples (0.66V vs. NHE). This film was composed of amorphous carbons doped with pyridine type nitrogen atoms on its surface. [ABSTRACT FROM AUTHOR]

Under potential cycling, fuel cell catalysts undergo dramatic losses in activity as a result of corrosion and catalyst surface change and dissolution. As transmission electron microscopy indicates, in the early potential cycles, two mechanisms are likely involved; namely, Pt particles growth and Pt dissolution. We reported that catalyst support plays a key role in enhancing catalyst activity and durability. Support based on boron doped diamond (DD) has an excellent corrosion resistance in an acidic environment and at high potential. Hence, BDD could be a good alternative to carbon. Also, ceramic materials, such as metal oxides, are promising candidates as catalyst supports. These materials can improve the oxygen reduction reaction (ORR) activity and durability due to possible interaction between catalyst and support. We have shown, as an example, the effect of support on ORR activity for two systems, Pd/C and Pd/TiO2. [ABSTRACT FROM AUTHOR]

Abstract: Two ways of reverse micelle (RM) method were investigated to prepare carbon-supported nano-sized LaMnO3 with high oxygen reduction activity. Hydrolysis precipitation in reverse micelle (HP-RM) method could give nano-sized particles of LaMnO3 easily because the particles size decreased with decreasing R w (=[H2O]/[surfactant]) value as well as nitrate concentration. The electrode prepared by the resulting particles showed high oxygen reduction activity as compared with that prepared by mechanical mixing-method. Furthermore, it was found that new RM method (ROP-RM) using KMnO4 as an oxidizer gave higher oxygen reduction activity than the HP-RM method, although particle size of LaMnO3 obtained by the ROP-RM method was almost same as that by RM-HP method. [Copyright &y& Elsevier]

The development of efficient electrode catalysts is of great significance for the evolution of microbial fuel cells (MFCs). In this work, Fe, N, and S co-doped porous carbon nanosheets (Fe–N–S/C) are synthesized by high-temperature sulfuration from Fe and N co-doped carbon (Fe–N/C). Fe–N–S/C not only exhibits superior oxygen reduction activity than Pt/C (20%) with a half-wave potential of 0.86 V, but also exhibits remarkable biocompatibility while facilitating electron transfer between microorganism and electrode. Satisfactorily, the MFCs with Fe–N–S/C as the catalysts for both cathode and anode show outstanding performance with a maximum power density of 923 ± 21 mW m−2 and favorable durability after 30 days of operation. Furthermore, 16srDNA results confirm that Fe–N–S/C effectively promotes the growth of functional colonies in anode biofilms, leading to high-efficient electricity production. The development of bifunctional electrode materials in this study can improve the performance of MFCs and facilitate their practical application. [Display omitted] • Fe–N–S/C is synthesized from Fe–N/C by high-temperature sulfuration. • Fe–N–S/C has remarkable biocompatibility and electrocatalytic activity. • MFCs equipped Fe–N–S/C for both anode and cathode exhibit enhanced performance. [ABSTRACT FROM AUTHOR]

Due to its better corrosion resistance and higher mechanical strength, 3D graphene is considered as a promising support for oxygen reduction reaction (ORR) electrocatalysts. However, the chemical inertness nature of graphene makes it difficult for Pt-based catalysts to anchor on. Compared with the spherical catalyst, although the Pt-based octahedral catalyst possesses higher mass activity (MA), it has fewer active sites per unit mass due to its larger size, which further hinders the application of 3D graphene as the support of Pt-based octahedral catalyst. Herein, we developed a facile and effective one-step hydrothermal method to fabricate nitrogen-doped porous graphene (NPG). The carbon material with an interconnected 3D framework and submicron macropores was then used to support Pt-Ni octahedral nanoparticles (NPs). The nitrogen not only increase the number of defects, but also improves the distribution of Pt-based octahedral catalysts on the graphene. The electrochemical surface areas (ECSA) of Pt-Ni/NPG reaches 5.5 times that before N-doping. Relative to commercial Pt/C (JM), Pt-Ni/NPG exhibits 6.8-fold enhancement in MA for 725.2 mA mg Pt −1 at 0.9 V RHE. Particularly, Pt-Ni/NPG showed only 8.6% loss in MA after 8000 cycles of the accelerated durability test, as compared to a sharp decrease of 56.2% for Pt/C after only 4000 cycles. In the accelerated durability test of carbon support, Pt-Ni/NPG also exhibited good durability relative to Pt-Ni/C. These results indicate that the Pt-based octahedral catalyst supported on NPG is expected to be applied to proton exchange membrane fuel cells (PEMFCs). [Display omitted] [ABSTRACT FROM AUTHOR]

Microbial fuel cells (MFCs) are a promising biotechnology that realizes the transformation of wastewater treatment from an energy consumption to an electricity generation process. However, the tedious process and the large resources consuming in preparing powder ORR catalysts are still non-negligible limiting factors for application. This study aims at proposing an energy-efficient method for preparing three-dimensional binder-free air cathode for MFCs: non-noble composite catalysts based on graphene and MnO 2 are synthesized directly on stainless steel fiber felt (SSFF) by pre-fixing and electro-reducing graphene oxide on SSFF (rGO-SSFF), and then in-situ depositing MnO 2 nanocatalysts on rGO-SSFF (rGO@MnO 2 -SSFF). The experimental results show that the ORR ability of rGO@MnO 2 -SSFF cathode is greater than that of Pt/C-CC cathode, even if the performance of rGO@MnO 2 powder catalyst is slightly lower than that of the traditional Pt/C catalyst. The excellent performance is found to be due to the three-dimensional framework-pore structure of SSFF which helps the prepared cathode possess larger electrochemical active area (8415.18 m2 m−3) than Pt/C-CC cathode (7518.13 m2 m−3). The proposed method provides a new way to reduce the cost (labor, materials and energy) of air cathode while ensuring the high electricity output of MFCs. [Display omitted] • The non-noble composite catalysts are synthesized on SSFF for preparing air cathode. • This catalyst loading method is low-consumption and eco-friendly. • The proposed cathode exhibits higher ORR activity than Pt/C-CC cathode. • The 3D framework-pore structure of SSFF helps achieve the high electric output. [ABSTRACT FROM AUTHOR]

A 3D macroporous stainless steel fiber felt (SSFF) is used as base material and a simple water bath method is adopted to directly load Pd nanocatalysts on SSFF to fabricate the air cathode of microbial fuel cells (MFCs). The optimum Pd loading is explored on the basis of the optimized PVP additive amount and reaction temperature. To attain a high ORR activity, a conductive carbon black filling layer is added into the 3D pores of Pd-SSFF. A series of physical and electrochemical tests are conducted to characterize the morphology, chemical composition and oxygen reduction activity and then the obtained cathodes are installed in MFCs for electricity production verification. The results show that the Pd-SSFF cathode at a Pd loading of 0.5 mg cm−2 (Pd-SSFF-0.5) achieves high output voltage and power density (492.65 mV, 390.79 mW m−2) which are comparable to the conventional Pt/C electrode (504.80 mV, 405.47 mW m−2). Furthermore, with Pd-SSFF-0.5 cathode the high-voltage platform duration of MFC in one operation cycle is 2.79 times of that of Pt/C electrode. Excellent mechanical properties (high pressure and corrosion tolerance), high electric energy output and simple fabrication prove it is an efficient strategy to improve the overall performance of MFCs using the obtained cathodes. • 3D macroporous SSFF is proposed as base material in air cathode. • Pd nanocatalysts is loaded directly on SSFF with the simple water bath method. • This loading method can replace the complex preparation process of powder catalysts. • Filling carbon black into the 3D pores of Pd-SSFF helps improving ORR performance. • Excellent mechanical properties and high electric output are achieved by Pd-SSFF cathodes. [ABSTRACT FROM AUTHOR]