Thx for the catch!
Fixed the math using chat gpt :P.
Reaction: 3CO2 + 12H2 -> C3H8 + 6O2
Number of moles of electrons (n): n = 3 * 4 = 12
Total charge (Q) in Coulombs: Q = (-395 * 1 * 100 * 3600 * 0.91 / 1000) * 12 * 96485
Voltage (V): V = -0.8
Total energy for given current density: E = Q * V
Moles of CO2 in 1 ton: n_CO2 = (1000 * 1000) / 44.01
Total charge for 1 ton of CO2: Q_total = (12 / 3) * n_CO2 * 96485
Adjusted charge considering Faradaic efficiency: Q_adjusted = Q_total * 0.91
Total energy for 1 ton of CO2: E_total = Q_adjusted * V
Convert to kWh: E_kWh = E_total * 2.778e-7 E_kWh ≈ 17707.4 kWh