A fuel cell was developed using borohydride solutions as the fuel. The cell consisted of an anode made of a Zr-Ni alloy, a cathode made of Pt/C, and a Na+ form Nafion membrane as the electrolyte. The borohydride-fueled cell showed an open-circuit voltage of 1.3 V, compared with 1.0 V for a hydrogen gas-fueled one. The anode exhibited a small polarization property compared with the cathode. The cathode polarization was the main reason for the cell voltage drop with increasing currents. When a Nafion membrane was used as the electrolyte, it was confirmed that cations false(Na+false) were the charge carrier in it. Compared with Nafion 112 membrane, Nafion 117 membrane demonstrated a considerable resistance to borohydride crossover and resulted in acceptable cell performance. However, there are several problems such as H2 evolution during operation, BH4− crossover, NaOH accumulation at the cathode, and NaBO2 accumulation at the anode in recent systems. Further effort is needed to develop the fuel cell using borohydrides as the fuel. © 2003 The Electrochemical Society. All rights reserved.

This paper is related to the hydrogen storage (H-storage) system composed of an alkaline solution that contains metal-hydrogen complex ions. The BH 4 − -complex ions stabilized when it is dissolved in aqueous KOH or NaOH to form homogeneous solutions. However, it is necessary to apply an appropriate catalyst for a high rate generation of hydrogen under atmospheric pressure and temperature conditions. The authors intended to develop catalysts suitable for the hydrolysis of BH 4 --complex ion solutions and found that Mg 2 Ni exhibits excellent catalytic functions in the hydrolysis, in particular, after the fluorination treatment (F-treatment). In this work, the effects of F-treatment on the rates of hydrolysis were evaluated between the hydrided and unhydrided Mg 2 Ni. No hydrogenation in addition to F-treatment is required in view of hydrolysis kinetics and cost-effectiveness.

Properties and characteristics of hydriding alloys are strongly dependent on surface compositions and morphologies. For instance, oxides such as La203 on AB5 alloys and ZrO2 on AB2, AB, and body-centered-cubic (BCC) alloys act as the barriers for the conversion of molecular and ionic hydrogen to atomic hydrogen at the surface, thus reducing the kinetics in both the gas-solid and electrochemical reactions.Alloy surfaces chemically treated by an aqueous F-ion containing solution have been developed to solve such problems. F-treated surfaces exhibit significantly improved characteristics in regard to the hydrogen uptakes and the protection against impurities and electrolyte solution. In addition, highly conductive metallic Ni layers can be formed on the surface of the alloy particles by the fluorination.The authors report the properties and characteristics of fluorinated hydriding alloys, mainly of a typical AB2 Laves phase material which represents the difficult activation characteristics and poor long-term durability during electrochemical charge/discharge cycles.