Deposition of Pd/graphene aerogel on nickel foam as a binder-free electrode for direct electro-oxidation of methanol and ethanol

Abstract

We reported a simple and green method to fabricate various palladium (0.8, 2.17, 7.65 wt%) loaded graphene aerogel deposited on nickel foam (Pd/GA/NF) as binder-free direct electrodes for electro-oxidation of methanol and ethanol. L-Ascorbic acid (vitamin C, VC) was used as a reducing agent in the process under a mild temperature of 40 °C. The morphology, chemical composition, and electrochemical performance of the prepared electrodes were characterized by optical microscopy, SEM/EDX, TEM, XRD, XPS, XRF, and cyclic voltammetry (CV), respectively. The XPS results revealed that both graphene oxide and Pd ions were simultaneously reduced by VC. The CV analysis revealed that the 7.65 wt% Pd/GA/NF electrode showed a maximum peak current density of 798.8 A g⁻¹ (forward to backward peak current density ratio (I_f/I_b) of 3.11), and 874 A g⁻¹ (I_f/I_b of 2.72) in methanol and ethanol electro-oxidation, respectively. The catalytic performance of the electrodes was enhanced with increasing the Pd loading. The results indicated that the 7.65 wt% Pd/GA/NF electrode exhibited a good electrocatalytic activity and an outstanding stability for alcohol electro-oxidation. The prolong CV scanning study (over 1000 cycles) showed that the 7.65 wt% Pd/GA/NF electrode achieved a better overall performance and stability in ethanol oxidation compared to methanol oxidation. The proposed electrode preparation method has a great potential for preparing various binder-free catalytic electrodes, which would be beneficial to the development of fuel cell application.