Nitrogen-doped graphene quantum dots as a support for Ni–Au nanoparticles: efficient electrocatalysts for ethanol and formate fuel cells using hydrogen peroxide as an oxidant

Abstract

Recent studies have shown that the networking and interaction between N, S, and CQDs activate reactions by creating additional active sites that bind more oxygen molecules. In this study, we used nitrogen-doped graphene quantum dots as a support for Ni–Au nanoparticles and investigated the influence of different Ni–Au ratios on the N-doped graphene quantum dots as an electrocatalyst for ethanol and formate oxidation. Indeed, three electrocatalysts containing gold and nickel nanoparticles are synthesized in 1 : 1, 1 : 3, and 3 : 1 (Ni₁Au₁, Ni₁Au₃, and Ni₃Au₁) ratios on the nitrogen-doped graphene quantum dots as a catalyst support by the reduction process. The synthesized electrocatalysts are characterized by XRD, FESEM, and EDX methods. The electrocatalytic activity of the Ni₁Au₁-NGQD, Ni₁Au₃-NGQD, and Ni₃Au₁-NGQD (nickel–gold–nitrogen-doped graphene quantum dot) electrocatalysts towards ethanol and formate oxidation are evaluated in half-cell and single-fuel cell configurations. The half-cell results confirm the superiority of the Ni₁Au₁-NGQD electrocatalyst towards oxidation of both fuels compared to the two other electrocatalysts, and the corresponding chronoamperometry shows its high stability. Therefore, the Ni₁Au₁-NGQD is used as an anodic electrocatalyst in a single fuel cell configuration using ethanol and formate as fuels and hydrogen peroxide as an oxidant. The maximum power density of 8.20 and 14.23 mW cm⁻² is obtained at 60 °C with 2 M ethanol and 4 M formate as the fuel in a direct ethanol–hydrogen peroxide fuel cell (DEHPFC) and direct formate–hydrogen peroxide fuel cell (DFHPFC), respectively.