Liuzzi competed for the Trulli team for five rounds of the inaugural all-electric series, but is unavailable this weekend due to a prior commitment to the GT Asia series.
GP3 driver Fontana will take over the second car alongside former Formula One ace and team boss Jarno Trulli.
Swiss driver Fontana is currently taking part in his third season in GP3 and has ginished on the podium on three occasions.
"I am so excited to get this opportunity to drive for Trulli Formula E in the final rounds of the season, and to be able to race next to Jarno is nothing but a privilege," the 22-year-old told Autosport.
"Now I have a lot to learn in the next 24 hours but I'm confident in the team and that I can produce a good result."
Incidentally, two other Swiss drivers will take part this weekend in London – Fabio Leimer for Virgin and Simona de Silvestro for the Andretti team.
In other driver changes for this weekend’s double header, local boy Oliver Turvey will make his series debut for China Racing while Sakon Yamamoto represents Aguri.