Substrate catalyzed formation of Au-Cu bimetallic nanoparticles as electrocatalyst for the reduction of dioxygen and hydrogen peroxide

Abstract

Bimetallic nanoparticles (BMNPs) offer a novel vision for enhancing the electrocatalytic activity due to their promising synergetic effects. In this study, bimetallic Au-CuNPs were directly attached on electrode surface by electroless deposition for the first time. Initially, AuNPs were fabricated on glassy carbon (GC) electrode by the reduction of HAuCl4 by hydrazine hydrochloride besides catalyzed by the substrate. SEM studies showed that the size of the deposited AuNPs was found to be 40 nm. The CuNPs were then formed on the AuNPs fabricated electrode by immersing it into the solution containing CuSO4 and hydrazine and the former act as a nucleation centre. The growth of CuNPs on AuNPs follows the seeding mechanism and the growth was monitored by SEM with respect to deposition time. The deposited Au-CuNPs were isotropic and uniform. The X-ray photoelectron spectroscopic (XPS) results confirmed the zero valent nature of both Au and Cu in the Au-CuNPs assembly. The electrocatalytic activity of the GC/Au-CuNPs electrode was examined towards the reduction of dioxygen and hydrogen peroxide (HP). It was found that the GC/Au-CuNPs electrode exhibited higher electrocatalytic activity by not only enhancing the reduction current of dioxygen and HP but also decreased their reduction overpotentials. Moreover, the deposition time dependent electrocatalytic activity was studied at Au-CuNPs modified electrode and it was found that 4 h deposition of CuNPs on AuNPs showed higher electrocatalytic activity in contrast to other electrodes. The limit of detection was found to be 73 nM (S/N = 3) and the sensitivity was 941 μA mM−1 cm−2 for HP at Au-CuNPs modified electrode.