Surface plasmon-enhanced activity and stability for methanol oxidation on gold caviar-like assembly under solar light

Abstract

The surface plasmon-enhanced catalytic performance of a gold caviar-like assembly (Au-CA) in methanol electrooxidation was investigated with and without simulated solar irradiation. An Au-CA catalyst synthesized by an ion sputtering method not only exhibited an excellent anodic peak current density (115.86 μA μg⁻¹) but also displayed long-term catalytic stability for methanol electrooxidation. The Au-CA catalyst also provided an anodic peak current density of 248.9 μA μg⁻¹ for methanol electrooxidation under simulated solar irradiation. This value corresponded to a 2.15-fold increase with respect to that in the absence of solar light irradiation in a deoxygenated solution of 1.0 M KOH and 1.5 M CH₃OH. The diffuse reflectance UV-vis absorption spectra and photoelectric response performance of the as-prepared Au-CA catalyst were investigated to understand the effectiveness of the surface plasmon resonance of Au nanoparticles for the enhancement of methanol electrooxidation performance. The results showed that the Au-CA catalyst exhibited a broad absorption peak at a wavelength of 515 nm with a red shift in comparison with that of a solution of Au nanoparticles. The photocurrent density of the Au-CA catalyst was 175.8 μA μg⁻¹ at an irradiation wavelength of 468 nm, which was 2.5 times higher than that at 640 nm (70.2 μA μg⁻¹) in a deoxygenated solution of 0.5 M Na₂SO₄. These findings suggested the potential of the new strategy for the improvement of the activity and durability of Au in methanol electrooxidation in direct methanol fuel cell technologies.