Colloidal nanomaterials have attracted significant interest in the field of high-performance catalyst synthesis. Additives (surfactants) are commonly used in colloid chemistry to control nucleation and growth of the nano-objects from a homogeneous solution. The action of these additives often yields colloidal particles of well-defined size, shape and composition thus being a crucial pre-requisite for systematic studies on structure-reactivity correlations.1-2 However, when left behind on the colloid surface the surfactants might affect its activity or change the selectivity towards certain reaction products by sterically altering reaction sites on the colloid surface. Approaches of surfactant removal shape from the nano-objects which do not change their size and shape are therefore highly desired.Herein, we report on a systematical investigation on various surfactant removal methods.Among the surfactant methods studied (including but not restricted to thermal annealing, chemical washing, plasma treatment, and exposure to ozone) photonic curing stands out. Photonic curing is an exposure of matter to intense and short (µs) light pulses. This approach of catalyst activation will exemplarily be demonstrated on the basis of Cu nanowire (Cu-NW) catalysts synthesized by an oleylamine route.3 Whereas the 3D-networks of the as-synthesized Cu-NW catalysts predominantly produce hydrogen as CO2RR product, photonically cured Cu-NWs show a high selectivity towards ethylene formation reaching a Faradaic efficiency of FEC2H4 = 42.4% (JC2H4 = -7.8 mA cm-2, E = -1.1V vs RHE) which can be maintained during prolonged electrolysis of 110 h. The almost quantitative surfactant removal by the photonic curing was confirmed by XPS analysis.A further beneficial effect of the photonic curing treatment is related to the substantially increased mechanical stabilization of the Cu-NW film on the support electrode induced by a ‘mild’ sintering of Cu-NWs which remains locally confined to their points of contact. A loss of catalyst material or delamination of the catalyst film from the support electrode during massive gas evolution can thus be prevented.Figure 1. SEM image of Cu-NWs and CO2RR product distribution at -1.1V vs RHE (1 h electrolysis) derived from catalysts treated by various procedures for the removal of the surfactant.