The aim of this proposal is to investigate H2 and CO-induced phenomena occurring at Pt- and Ru-based catalysts by time-resolved XAS experiments in the liquid-phase. Previous multi-technique experiments, comprising Pt L3-edge XAS (CH-5204), revealed that Pt nanoparticles (NPs) restructure in the presence of H2 in the gas-phase; a similar behaviour is expected also for Ru, which is more reactive than Pt. Moreover, in a very recent high-energy XRPD/PDF experiment (CH-6371), we found that both catalysts restructure in the presence of H2 also in liquid phase, at a short time-scale (1-2 min). Here we want to perform time-resolved Pt L3-edge and Ru K-edge XAS to collect complementary information on adsorbate-induced NPs restructuring, extending the interest from H2 to CO. The experiment will help in bridging the gap of knowledge between phenomena occurring in gas and liquid phase, which are relevant both for fundamental research and for industrial catalysis.