After Real Madrid cut the gap by beating Elche on Saturday the Spanish champions responded by romping to a comfortable victory.
Dani Olmo and Joao Cancelo also struck for Hansi Flick’s side, who host Newcastle in the Champions League on Wednesday.
Club members streamed to the stadium before the game to vote in the club’s presidential elections, with either Joan Laporta or Victor Font to be announced the new chief later on Sunday night.
“Three points more, one game less and we scored five goals, it was good to see,” Flick told reporters, although he called for a sharper all-round performance on Wednesday.
“We have to be focused for the next game because Newcastle is a great team.
“I’m not negative, I just think about what can be better.”
After the 1-1 draw in Newcastle in the last-16 first leg, Flick left Lamine Yamal on the bench and handed youngster Xavi Espart his first start, at right-back.
Barcelona were handed two penalties by a sorry Sevilla side to get off to the perfect start at the partially-rebuilt Camp Nou, which finally received clearance to open the north stand.
Around 56,000 fans attended and they were able to watch a fairly straightforward rout of the Andalucians, 14th.
Djibril Sow clumsily clipped rampaging Barca full-back Cancelo in the box and Raphinha dinked home from the spot to open the scoring in the ninth minute.
The Brazilian winger was afforded another penalty to put Barca two goals up when Jose Angel Carmona, lying on the floor, handled as Cancelo tried to dribble around him.
This time Raphinha fired it low to the left and although Odysseas Vlachodimos went the right way he could not keep it out.
The hosts netted a third in the 38th minute when Marc Bernal’s deflected cross from the left found Olmo, who produced a clinical finish.
Sevilla pulled one back before the break when Juanlu Sanchez got in behind Cancelo and crossed for Oso to score unmarked at the back post.
Raphinha completed his hat-trick early in the second half with a heavily deflected shot as Barca strolled in the spring sunshine.
“Playing like this it’s hard for teams to beat us,” Raphinha told DAZN.
“I love this club, and the way to respond from the love I receive from the fans is by scoring goals and kissing the badge.
“Until the last day (I’m here) I will give the best of myself.”
Cancelo capped an impressive attacking display with a goal of his own, driving into the box and finishing through Vlachodimos’s legs.
– Gavi’s return –
Barca coach Flick sent on 21-year-old midfielder Gavi for the final 10 minutes after a severe knee injury, and Ronald Araujo handed him the captain’s armband.
“It has been very tough, if I’m honest,” Gavi told DAZN of his recovery process, on his first appearance since August.
The Spain international also missed most of the 2023/24 season out injured.
“This time was much harder than the last time, I was having a bad time of it. It was more of a painful process and it was harder for me day to day,” continued Gavi.
“But this feeling (to be back at) Camp Nou, with my people, with the fans and all my team-mates is unique and I’m really happy.”
Sow pulled another one back for Sevilla in stoppage time, nodding home Oso’s cross, with Barcelona already thinking about Newcastle’s visit on Wednesday.
“Barcelona are very good… I think that the two quick penalties (given away) hurt us a lot, after that it was a difficult game,” said Sevilla defender Nemanja Gudelj.