  Space-borne gravitational wave detectors like TianQin are expected to detect
GW signals emitted by the mergers of massive black hole binaries. Luminosity
distance information can be obtained from GW observations, and one can perform
cosmological inference if redshift information can also be extracted, which
would be straightforward if an electromagnetic counterpart exists. In this
paper, we concentrate on the conservative scenario where the EM counterparts
are not available, and comprehensively study if cosmological parameters can be
inferred through a statistical approach, utilizing the non-uniform distribution
of galaxies as well as the black hole mass-host galaxy bulge luminosity
relationship. By adopting different massive black hole binary merger models,
and assuming different detector configurations, we conclude that the
statistical inference of cosmological parameters is indeed possible. TianQin is
expected to constrain the Hubble constant to a relative error of about 4%-7%,
depending on the underlying model. The multidetector network of TianQin and
LISA can significantly improve the precision of cosmological parameters. In the
most favorable model, it is possible to achieve a level of 1.7% with a network
of TianQin and LISA. We find that without EM counterparts, constraints on all
other parameters need a larger number of events or more precise sky
localization of GW sources, which can be achieved by the multidetector network
or under a favorable model for massive black hole mergers. However, in the
optimistic case, where EM counterparts are available, one can obtain useful
constraints on all cosmological parameters in the Lambda-CDM cosmology,
regardless of the population model. Moreover, we can also constrain the
equation of state of the dark energy without the EM counterparts, and it is
even possible to study the evolution of EoS of the DE when the EM counterparts
are observed.

Cosmology and Nongalactic Astrophysics;General Relativity and Quantum Cosmology