Effect of the configurations of N and S atoms on electrochemical performance of Pt for methanol oxidation

Designing a highly efficient catalyst for methanol oxidation largely depends on fabricating a new material that exhibits a superior synergistic effect with Pt. Until now, heteroatom-doped graphene has been used as a promising material for deposition of highly ultrafine Pt particles. Also, each heteroatom has different configurations that affect the catalytic activity of the catalyst. N and S-doped graphene layer includes different types as a thiophenic S and oxidized S and different N types as a pyrrolic, graphitic, and pyridinic N. In this study, the effect of different types of S and N atoms (S type and N type) on methanol oxidation was investigated. For this, N, S co-doped graphene layer and its pyrolysed form at 500 °C were obtained and labeled N-S-rGO and p-N-S-rGO. Then, Pt was deposited chemically on N-S-rGO and p-N-S-rGO. The obtained catalysts (Pt–N-S-rGO and Pt-p-N-S-rGO) were characterized by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDX), mapping, X-ray powder diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Electrochemical performance of prepared electrodes for methanol oxidation was investigated by cyclic voltammetry (CV), electrochemical impedance (EIS), and amperometric measurements. Current densities of Pt–N-S-rGO and Pt-p-N-S-rGO electrodes were determined as 139.4 mA/cm² and 86.17 mA/cm², respectively. Besides, Pt–N-S-rGO exhibited higher anti-CO poisoning properties than Pt-p-N-S-rGO. It was concluded that the strong interaction between the oxidized S group and Pt caused Pt deposited on the graphene layer with ultra-small size and homogeneous, which increased catalytic activity of Pt–N-S-rGO towards methanol oxidation. Furthermore, it was found that Pt–N-S-rGO revealed 95.34% stability even after the long-term accelerating test.