Borohydride electrooxidation on Au and Pt electrodes

Direct borohydride fuel cells (DBFCs) are attractive energy generators for powering portable electronic devices, mainly due to their high energy density and number of electrons per borohydride ion. However, the lack of a highly efficient electrocatalyst for the borohydride oxidation reaction limits the performance of these devices. The most commonly studied electrocatalysts for this reaction are composed of gold and platinum. Nevertheless, for these metals, the borohydride electrooxidation reaction mechanism (BOR) is not completely understood, and the total oxidation reaction, involving eight electrons per BH4− species, competes with parallel reactions, with a lower number of exchanged electrons and/or with heterogeneous chemical hydrolysis. Considering the above-mentioned issues, this work presents recent advances in the knowledge of the BOR pathways on polycrystalline (bulk) Au and Pt electrocatalysts. It presents the studies of the BOR reaction on Au and Pt electrodes using in situ Fourier Transform Infrared Spectroscopy (FTIR), and on-line Differential Electrochemical Mass Spectrometry (DEMS). The spectroscopic and spectrometric data provided physical evidence of intermediate species and the formation of H2 in the course of the BOR as a function of the electrode potential. These results enabled to advance in the knowledge about the BOR pathways on Au and Pt electrocatalysts.

► Mechanism of the borohydride oxidation reaction. ► Electrocatalysis of the borohydride oxidation reaction on gold and platinum eletrodes. ► Heterogeneous hydrolysis of borohydride on direct borohydride fuel cells. ► FTIR and mass spectrometry: key techniques for studying the borohydride oxidation reaction.