The centre-back passed his medical with the Catalan club on Friday, completing his transfer from Dutch team AZ Alkmaar, and has penned a five-year deal with the Spanish side.
Mexico's participation in the Gold Cup meant the 23-year-old was unable to officially complete his transfer until now but he is keen to help his new team fulfil ambitions next season.
In quotes published by El Mundo Deportivo, Moreno said: "The future [of the club] is to be built on young people, all with an overwhelming desire. The intent is to win a cup or get into European competition.
''I am happy, calm and excited. I'm arriving in Spain with my batteries charged and I'm eager to meet my new team-mates. I consider myself to be an ambitious player. I always have the desire to win.''
Moreno will join up with the squad's pre-season preparations after moving to Espanyol for an undisclosed fee, believed to be in the region of €3 million.