Pulsed Laser Defect Engineering in Liquid (PUDEL) of platinum nanoparticles with UV-laser pulses in a flat liquid jet leads to the formation of reactive oxygen species and subsequent increase of the nanoparticle zeta potential (surface charge density) and enhancemend of the catalytic activity.

Abstract

The performance of heterogeneous catalysts is governed by their physicochemical surface properties, requiring respective engineering strategies. Pulsed laser defect engineering in liquid (PUDEL) has emerged as a scalable green technology to activate and dope oxide-based catalysts. This study investigates UV-PUDEL effects on the catalytic activity and nanostructure of metallic, colloidal platinum nanoparticles (Pt NPs). As will be shown, the Pt NP size and polydispersity were maintained after UV-PUDEL, while the zeta potential and hence surface charge density increased by 40%. X-ray photoelectron spectroscopy (XPS) revealed ∼33% surface-near platinum oxidation, unaffected by UV-PUDEL. Control experiments using radical scavengers and nitrogen-saturated water support the hypothesis that radical oxygen species (ROS) drive these effects. Electrocatalytic studies demonstrated an almost twofold electrochemically active surface area (ECSA) and improved oxygen reduction reaction (ORR) activity of the Pt/C catalysts when UV-PUDEL was applied to the Pt NPs prior to the carbon deposition. In contrast, a direct laser processing of Pt/C resulted in an activity loss due to a ROS-induced carbon degradation. Mechanistic insights suggest that the laser-induced ROS formation is directly linked to the Pt NP. These findings establish UV-PUDEL as a scalable post-processing strategy to enhance the catalytic activity of oxide and metal-based catalysts.