The borohydride oxidation reaction on La-Ni-based hydrogen-storage alloys.
This work provides insights into the processes involved in the borohydride oxidation reaction (BOR) in alkaline media on metal hydride alloys formed by LaNi(4.7)Sn(0.2)Cu(0.1) and LaNi(4.78)Al(0.22) with and without deposited Pt, Pd, and Au. The results confirm the occurrence of hydrolysis of the borohydride ions when the materials are exposed to BH(4)(-) and a continuous hydriding of the alloys during BH(4)(-) oxidation measurements at low current densities. The activity for the direct BOR is low in both bare metal hydride alloys, but the rate of the BH(4)(-) hydrolysis and the hydrogen-storage capacity are higher, while the rate of H diffusion is slower for bare LaNi(4.78) Al(0.22). The addition of Pt and Pd to both alloys results in an increase of the BH(4)(-) hydrolysis, but the H(2) formed is rapidly oxidized at the Pt-modified catalysts. In the case of Au modification, a small increase in the BH(4)(-) hydrolysis is observed as compared to the bare alloys. The presence of Au and Pd also leads to a reduction of the rates of alloy hydriding/de-hydriding.
Instituto de Quimica de Sao Carlos, Universidade de Sao Paulo, Avenida Trabalhador Sancarlense, 400 Parque Arnold Schmidt, CP 780 13560-970, Sao Carlos, SP (Brazil).
Waldemir J
WJ
Paschoalino
Stephen J
SJ
Thompson
Andrea E
AE
Russell
Edson A
EA
Ticianelli
alloys; borohydride oxidation reaction; galvanic displacements; hydrogen storage; metal hydrides