Rotating Disk Electrode (RDE) Investigation of BH₄⁻ and BH₃OH⁻ Electro-oxidation at Pt and Au: Implications for BH₄⁻ Fuel Cells

Abstract

We present a thorough electrochemical study of the mechanism of borohydride oxidation on gold and platinum surfaces via cyclic voltammetry and rotating disk and ring-disk electrode voltammetry. We have paid particularly close attention to the number of electrons transferred (from a theoretical maximum of 8e−), values of the heterogeneous charge transfer rate constant (kb), the presence of coupled chemical reactions, and adsorbed intermediates. We find that the nature of the electrode (Pt, Au) plays an important role in all of these processes and we present a detailed mechanistic analysis in light of the above-mentioned results. Our study suggests that Pt will significantly outperform Au for a direct borohydride fuel cell, providing similar electron recovery at much lower anode potentials.