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Direct borohydride fuel cells (DBFCs) exhibit the potential for a wide range of applications due to their high energy and power density; however, the hydrolysis of BH 4 − significantly limits the use of DBFCs. In this paper, PdNi x -B/carbon nanotubes (PdNi x -B/CNTs) (x = 0, 0.3, 0.6, 0.9) composites have been prepared by a chemical reduction method in which PdNi x -B nanoparticles of approximately 3.5 nm are grown on the surface of carbon nanotubes. A cell was assembled with PdNi x -B/CNTs as the anode catalyst, a polymer fibre membrane (PFM) as a substitute for the Nafion membrane and LaNiO 3 as the cathode catalyst. The results show that the Ni element displays an ability to balance the competition between the hydrolysis and oxidation of BH 4 − . A peak power density of 105 mW cm −2 (x = 0.9) was achieved at 25 °C. However, the highest fuel efficiency of 69% was achieved at x = 0.3, and the corresponding power density was 87 mW cm −2 , which represents the best comprehensive performance of these DBFCs. [ABSTRACT FROM AUTHOR]

Similar to MXene, MAB is a group of 2D ceramic/metallic boride materials which exhibits unique properties for various applications. However, these 2D sheets tend to stack and therefore lose their active surface area and functions. Herein, an amorphous cobalt nickel boride (Co–Ni–B) nanocomposite is prepared with a combination of 2D sheets and nanoparticles in the center to avoid agglomeration. This unique structure holds the 2D nano-sheets with massive surface area which contains numerous catalytic active sites. This nanocomposite is prepared as an electrocatalyst for borohydride electrooxidation reaction (BOR). It shows outstanding catalytic activity through improving the kinetic parameters of BH 4 − oxidation, owing to abundant ultrathin 2D structure on the surface, which provide free interspace and electroactive sites for charge/mass transport. The anode catalyst led to a 209 mW/cm2 maximum power density with high open circuit potential of 1.06 V at room temperature in a miniature direct borohydride fuel cell (DBFC). It also showed a great longevity of up to 45 h at an output power density of 64 mW/cm2, which is higher than the Co–B, Ni–B and PtRu/C. The cost reduction and prospective scale-up production of the Co–Ni–B catalyst are also addressed. [Display omitted] • DBFC with Co–Ni–B nanocomposite as anode catalyst exhibited P max = 209 mW/cm2 which is over twice higher than PtRu/C. • MXene-like structure enhanced the exposure of active metallic species and the mass transfer. • The assembled DBFC has good stability of retaining 91.2% of the output voltage after 45 h. • The narrow band gap of Co–Ni–B nanocomposite urges the charge transfer kinetic. [ABSTRACT FROM AUTHOR]

In recent years, the oxygen reduction reaction (ORR) performance of N-doped carbon catalysts has made great progress and is now comparable to that of commercial Pt/C. However, the rich porous features of N-doped carbon catalysts give them a very low bulk density, which leads to problems in oxygen mass transfer due to water flooding when they are used as the cathode in fuel cells. Herein, a controllable mesoporous surface of nitrogen-doped yolk-shelled carbon spheres (N-YS-CS) with an extremely regular particle size was synthesized. The mesopores of the N-YS-CS effectively store the hydrophobic agent and form robust hydrophobic tunnels within the close-packed N-YS-CS units, forming an excellent structure for mass transfer at the cathode. This elaborately constructed hydrophobic cathode structure has a larger triple-phase interface than traditional carbon paper in an electrolyte-penetration-type direct methanol fuel cell (DMFC) with a polymer fiber membrane (PFM), and delivers a high power density (55 and 142 mW cm −2 at 25 °C and 60 °C, respectively) and discharge stability (a run time of over 210 h). [ABSTRACT FROM AUTHOR]

The Au@Co-B nano-particles are prepared by chemical reduction and used as anode catalyst in direct borohydride fuel cells (DBFCs). The physical and electrochemical properties of the catalyst are investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and fuel cell tests. The physical characterisation demonstrates that the crystalline Au particles are wrapped by amorphous Co-B, and the average size of Au@Co-B particles are about 15 nm. The fuel cell tests prove that the kinetics property of Au@Co-B is improved significantly and material cost reduced obviously compared with pure Au catalyst for DBFC. The maximum power output of 85 mW cm −2 is achieved at 25 °C for this cell without using any ion exchange membranes. This power density performance is also better than some noble metal and bimetallic anode in DBFCs which reported in literatures. And this cell also has a good durability, with no attenuation observed after 80 h of operation. [ABSTRACT FROM AUTHOR]

Abstract: LaNi0.9Ru0.1O3 as cathode catalyst for a direct borohydride fuel cell (DBFC) was synthesized and investigated for the first time. The electrochemical experiments indicated that perovskite-type oxide LaNi0.9Ru0.1O3 exhibited higher electrochemical performance compared with LaNiO3, which suggested incorporation of element Ru into LaNiO3 could further improve the catalytic ability for oxygen reduction reaction (ORR) in alkaline solution. LaNi0.9Ru0.1O3 catalyst was found to have good tolerance of BH4 −. Meanwhile the maximum power density of 171mWcm−2 was obtained at 65°C without using any precious ion exchange membrane. A life test indicated that the DBFC displayed no significant degradation for about 70h testing. The electrochemical data suggested that LaNi0.9Ru0.1O3, which provided a simple way to construct DBFCs without using any ion exchange membrane, might be promising cathode catalyst with high performance and low cost for DBFCs. [Copyright &y& Elsevier]

Abstract: Co-B amorphous alloy powders have been synthesized by chemical reduction of cobalt chloride with potassium borohydride in an aqueous solution. We find that this alloy can be used as an anode catalyst for a direct borohydride fuel cell (DBFC). This catalyst exhibits excellent electrocatalytic activity. An essential power output of 220mWcm−2 has been achieved at 15°C, and a life test last for 160h with no attenuation has been observed. The amorphous structure of the CoB alloy is still stable after the life test. [Copyright &y& Elsevier]

Abstract: In this paper, cobalt(II) oxide (CoO) has been used as an anode catalyst in a direct borohydride fuel cell (DBFC). The microstructure of CoO has been characterised by X-ray diffraction. The cell performance and short-term performance stability of the DBFC using the CoO as anode catalyst have been investigated. At the optimum conditions, the maximum power density of 80mWcm−2 has been achieved at 30°C for this cell without using any precious metals and ion exchange membranes. Results from XRD, TEM, and XPS analysis confirm that the good performance of the fuel cell is attributed to the co-operation of CoO and CoB which formed from CoO during the operation. [Copyright &y& Elsevier]