I will discuss recent collaborative studies on the potential of advanced GW detectors for improving the current knowledge of cosmological parameters and testing the dark-energy sector, using standard sirens. We consider second generation network made by the two advanced LIGO detectors+advanced Virgo+LIGO India+Kagra, and third-generation detectors such as the Einstein Telescope and Cosmic Explorer. We construct mock catalogs of standard sirens, considering different scenarios for the local merger rate and for the detection of an electromagnetic counterpart. We first study how standard sirens can improve the determination of H0 and OmegaM in LCDM, with respect to the current results from Planck CMB data, BAO and SNe. We then study how standard sirens at second- or third-generation GW detectors, alone or in combination with other cosmological datasets, can give information not only on H0 and Omega_M, but also on the dark energy sector, considering both a non-trivial dark energy equation of state and modified GW propagation.