Metal nanoparticles (NPs) have been studied extensively as catalysts due to their high activity. However, the application of metallic nanostructures in catalytic reactions is hampered by their uncontrollable performance due to their reconstruction in reactive environments. Here, controllable restructuring of silver NPs in the reactive environment has been achieved to increase their activity. Surface restructuring of the as-synthesized silver NPs was monitored in situ by UV-vis spectra. Kinetic analysis, transmission electron microscopy (TEM), and molecular simulation were conducted to investigate the mechanism of this process. Results indicate that this reaction-driven restructuring leads to the formation of reactive high-index facets on silver NPs. In the reduction of 4-nitrophenol by sodium borohydride, silver NPs with extremely high catalytic activity (surface-area-normalized rate constant of 13.22 s(-1) m(-2) L) were obtained Via accurately controlled surface restructuring of silver NPs obtained by UV irradiation. (C) 2014 Elsevier Inc. All rights reserved.