Search

A cathode of zinc-air fuel cells (ZAFCs) comprises a catalyst layer and a diffusion layer. We propose a new type of cathode, which overcomes the disadvantages of a double-layer cathode used in ZAFCs. To improve the performance of the single-layer cathode, dispersing the particles and reducing their size in the cathode mixture were conducted. The single-layer cathode had the same hydrophobicity as with the diffusion layer of the double-layer cathode and showed better electrochemical properties than the catalyst layer of the double-layer cathode. The single-layer cathode had a dense microstructure and a flat surface. The electrochemical performance and mechanical strength of the single-layer cathode were superior to those of a double-layer cathode. We showed single-layer cathode cell had better electrochemical performance than the double-layer cathode cell through a newly designed flexible-tubular-type ZAFC. [ABSTRACT FROM AUTHOR]

This study was conducted to develop new fabrication techniques and achieve improved performance of the cathode in liquid fuel cells. An integrated electrode with a sandwich-structured MnCo 2 O 4 /NC/MnO 2 catalyst was prepared by in-situ growth on nickel foam. The resulting integrated electrode was tested as the cathode of the alkaline direct methanol fuel cell (DMFC) and direct borohydride fuel cell (DBFC). The data indicated peak power density of 12.22 mW cm−2 for DMFC, and 33.65 mW cm−2 for DBFC. The in-situ growth of the MnCo 2 O 4 /NC/MnO 2 catalyst layer, without an organic binder, indicated a superior catalytic activity to that of MnCo 2 O 4 and MnCo 2 O 4 /NC. Moreover, stability test conducted at a constant-current discharge of 10 mA cm−2 for the integrated cathode-based DBFC revealed excellent stability for about 350 h. Compared to that of traditional cathode prepared by doctor-blade method, traditional cathode showed a significantly diminished discharge voltage. Thus, the highly dispersed nanocatalysts and the macroporous nickel foam accelerated the intrinsic catalytic activity and mass transfer in the cathode. This work provides a new strategy for the preparation and structure optimization of fuel cell electrodes. [Display omitted] • An integrated cathode with sandwich-structured MnCo 2 O 4 /NC/MnO 2 catalyst was prepared. • The sandwich-structured catalyst was prepared by in-situ growth on nickel foam (NF). • The integrated cathode was tested in alkaline DMFC and DBFC. • The cell stability was enhanced for the dispersed nanocatalysts and macroporous NF. [ABSTRACT FROM AUTHOR]

Nd 0.9 Ln 0.1 BaCo 2 O 6- δ (NLnBCO, Ln = La, Sm, Gd) materials are synthesized by EDTA-citrate method. The effects of rare earth element doping on crystal structure, thermal expansion behavior, electrical conductivity and electrochemical properties are investigated. Nd 0.9 Ln 0.1 BaCo 2 O 6- δ crystallizes in tetragonal symmetry with the space group P4/mmm. It is found that both the unit cell volume and the average valence of cobalt in NLnBCO increase, whereas the oxygen vacancy content (δ value) decreases with the gradual enlargement of the radius of the doped rare earth elements. XPS and O 2 -TPD results prove that the surface oxygen adsorption ability of NLnBCO improves gradually with the steady increase of Co4+ concentration in the material. The electrochemical impedance spectroscopy measurement results indicate that among the doped materials, Nd 0.9 La 0.1 BaCo 2 O 6- δ exhibits the lowest polarization resistance of 0.083 Ω cm2 at 700 °C in air. The anode-supported fuel cell constructed with this cathode shows a power output of 1.045 W cm−2 at 700 °C, and stable current density of 1.7 A cm−2 has been obtained with the load of 0.6 V for prolonged 100 h consecutive measurement. The rate limiting step of the oxygen reduction reaction (ORR) is the charge transfer process on Nd 0.9 La 0.1 BaCo 2 O 6- δ cathode. Our studies prove that doping La3+ with larger radius than Nd3+ is an effective way to promote the ORR reaction on NdBaCo 2 O 6- δ cathode. • The effects of rare earth element doping on the electrochemical properties of Nd 0.9 Ln 0.1 BaCo 2 O 6- δ are investigated. • La3+ doping improves the surface oxygen adsorption ability of Nd 0.9 Lan 0.1 BaCo 2 O 6- δ. • The anode-supported fuel cell constructed with Nd 0.9 Lan 0.1 BaCo 2 O 6- δ cathode shows a power output of 1.045 W cm−2 at 700 °C. [ABSTRACT FROM AUTHOR]

Designing affordable high efficient oxygen reaction (ORR/OER) electrocatalyst is a major task for promoting sustainable energy conversion batteries (such as Zn-air batteries and fuel cells). Herein, a bifunctional oxygen reaction electrocatalyst with excellent activity and stability constructed using the peasecod-like N-doped carbon nanotubes (N/CNT) in situ confinement encapsulate bimetallic FeCu alloy (FeCu–N/C). The bimetallic FeCu alloy embedded into N/CNT that inhibits serious polymerization of copper, increases Fe/Cu–N bimetallic active sites, improves conductivity, reduces the energy barrier of oxygen reaction and speeds up reaction kinetics, thus obtaining efficient ORR/OER performance. The optimal FeCu–N/C electrocatalyst reveal more positive half-wave potential for ORR, smaller overpotential for OER and lower ORR/OER potential gap than those of commercial grade Pt/C, IrO 2 and many reported catalysts. Moreover, the zinc-air batteries constructed using FeCu–N/C as the air electrode indicate the high power density and excellent stability. The alkaline anion exchange membrane fuel cells assembled with FeCu–N/C as cathode also exhibit enhanced power density compared to single metal-based catalysts (Fe–N/C and Cu–N/C). This work demonstrates potential use of FeCu–N/C for energy conversion and storage applications, provides a new sight for the reasonable design of bifunctional oxygen reaction electrocatalysts. Image 1 • A bifunctional oxygen reaction catalyst constructed using FeCu alloy encapsulated in peasecod-like N-rich carbon nanotubes. • The FeCu alloy increases Fe/Cu-N bimetallic active sites, conductivity and electrocatalytic oxygen reaction activity. • The FeCu 0.3 -N/C exhibited the low ORR/OER potential gap (△ E) of 0.777 V and extraordinary stability. • The FeCu 0.3 -N/C reveals superb cathode catalytic activity in zinc-air batteries and anion exchange membrane fuel cells. [ABSTRACT FROM AUTHOR]

Development of non-noble metal cathode catalysts was a continuous hotspots of fuel cell research. In this work, the CoO nanorods/C with different mass content of CoO were prepared by hydrothermal method and were investigated as cathode catalysts in direct borohydride fuel cell. The CoO nanorods exhibited an average length about 1–2 μm and an average diameter about 15 nm. The 10 wt% CoO nanorods/C achieved the best oxygen reduction reaction (ORR) activity compared to the 5 wt% CoO nanorods/C and 20 wt% CoO nanorods/C. The onset reduction reaction potential of the 10 wt% CoO nanorods/C catalyst toward ORR was 0.821 V (vs. reversible hydrogen electrode), and the number of electron transfer was about 4.01. The ORR on the catalyst was mainly based on an appropriate four-electron reaction pathway. The half-wave potential difference of the 10 wt% CoO nanorods/C after 5000 cycles was 26 mV, suggesting a good catalytic stability. The DBFC using the cathode catalyst achieved a maximum power density of 410 mW cm−2 at 60 °C. The experimental results confirmed that the CoO nanorods/C had excellent catalytic performance in DBFCs. Image 1 • CoO nanorods/C was prepared by hydrothermal method. • An appropriate 4e reaction was realized on CoO nanorods/C towards ORR. • CoO nanorods/C had much better stability than Pt/C towards ORR in alkaline solution. • DBFC using CoO nanorods/C cathode achieved a maximum power density of 410 mW cm−2. [ABSTRACT FROM AUTHOR]