Integrated technique of pulsed laser irradiation and sonochemical processes for the production of highly surface-active NiPd spheres

Abstract The development of highly surface-active nano-sized and submicron particles with well-defined features is a promising approach in regulating various physicochemical properties of materials for different applications. A new hybrid technique involving pulsed laser irradiation and sonochemical processes for the production of Pd nanoparticles, NiPd alloys, and ZnO and Ag/graphene oxide (GO) composites was developed herein. An unfocused pulsed laser (neodymium-doped yttrium aluminum garnet [Nd:YAG] laser pulse with a wavelength of 532 nm) was used to irradiate a mixture of colloidal Ni solution obtained by ablation and PdCl2, resulting in the formation of highly surface-active NiPd under continuous sonication at 40 kHz. The physicochemical properties of the synthesized materials were analyzed by X-ray diffraction (XRD), ultraviolet–visible (UV–vis) spectroscopy, field-emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HR-TEM), and dynamic light scattering (DLS). To investigate their potential uses, the alloys were employed as electrocatalysts in the hydrogen evolution reaction (HER). Notably, the NiPd synthesized by the integrated process exhibited higher HER activity in a 1 M KOH solution (overpotential of 38 mV at 1 mA/cm2) than the material obtained via pulsed laser irradiation alone (44 mV). The enhanced HER performance of the NiPd alloy was attributed to the synergistic effects of the integrated pulsed laser irradiation and sonochemical processes, affording NiPd particles displaying active surface defects and shape homogeneity. These features resulted in high electronic conductivity and low internal resistance of the material. The proposed hybrid technique could be utilized in the upscaling production of various functional materials with controlled properties.