Investigation of stability of gold nanoparticles modified zinc–cobalt coating in an alkaline sodium borohydride solution

Abstract

The electrochemical stability and durability of ZnCo alloy thin layers deposited on the titanium surface (denoted as ZnCo/Ti) and those modified by small amounts of Au nanoparticles (denoted as AuZnCo/Ti) prepared via the electrochemical metal deposition technique and a simple galvanic displacement have been investigated in alkaline sodium borohydride (NaBH₄) solutions. The physical properties of the fabricated AuZnCo/Ti catalysts have been examined using field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDX) and inductively coupled plasma optical emission spectroscopy (ICP-OES). The electrocatalytic activity of the ZnCo/Ti and AuZnCo/Ti catalysts toward the oxidation of NaBH4 has been evaluated in an alkaline medium using cyclic voltammetry (CV) and chronoamperometry (CA), whereas the catalytic efficiency of the catalysts for the hydrolysis reaction of NaBH₄ has been also examined by measuring the amount of generated hydrogen via the classic water-displacement method. It has been determined that the modification of the ZnCo alloy coating by Au nanoparticles apparently improves not only the morphology and structure of the catalyst, but also the activity and stability of the one for the oxidation of NaBH₄ in an alkaline medium as compared to those of ZnCo/Ti and bare Au. The AuZnCo/Ti catalysts that have Au loadings of 63 and 306 µg cm^–2 give ca. 12 and 11, respectively, times higher NaBH₄ oxidation current densities as compared to those of the bare Au catalyst. Moreover, the AuZnCo/Ti catalysts catalyze the hydrolysis reaction of NaBH₄ in alkaline solutions.