In situ infrared (FTIR) study of the borohydride oxidation reaction

The direct borohydride fuel cell (DBFC) is an interesting alternative for the electrochemical power generation at lower temperatures due to its high anode theoretical specific capacity (5Ahg-1). However, the borohydride oxidation reaction (BOR) is a very complex eight-electron reaction, influenced by the nature of the electrode material (catalytic or not with respect to BH4- hydrolysis), the [BH4-]/[OH-] ratio and the temperature.In order to understand the BOR mechanism, we performed in situ infrared reflectance spectroscopy measurements (SPAIRS technique) in 1 M NaOH/1 M NaBH4NaBH4 with the aim to study intermediate reactions occurring on a gold electrode (a poor BH4- hydrolysis catalyst). We monitored several bands in B–H (1184 cm−1) and B–O bond regions (1326 and 1415 cm−1), appearing sequentially with increasing electrode polarisation. Thanks to these experimental findings, we propose possible initial elementary steps for the BOR.