I thought it produce a 1 liter mixture of hydrogen and oxygen? That would be 0.66L (0.03 mole) Hydrogen and 0.33L Oxygen. It could even be less because the mixture was bubbled through water at 91 degrees so the mix is probably not at STP.He produced 1 liter of hydrogen gas, which is 0.044643 moles, because 1 mol H2 = 22.4L
I agree with your figure for the input power.
Revising the figures for the output gives..
(0.03 moles H2) * (237.5 kJ/mol) = 7125JThe output energy (from combusting the hydrogen is potentially) =
with the efficiency working out at about
(7125/15163) * 100 = 47%