Lol I don’t blame him. Although this has definitely peaked my interest as well.
You basically need to use H2O but the O is an isotope (generally the most common is 18O instead of the usual 16O). It’s also not that cheap lol. D2O (instead of H2O) is cheaper, but the hydrogens and deuteriums do hydrogen-exchange super easily, so if you used that, you end up with NaOD, but then the D can exchange very readily with the H, so you lose track of it when it becomes NaOH. If you use the 18OH2 instead, you just have to trace the oxygen, and the hydrogen exchange no longer matters. This is actually what they use in metabolic experiments as well. Whether or not this would work for electrolysis… no idea lol, but I would imagine it could be applied with some careful monitoring.
Other fun little high school chemistry experiments: Making slime and making a bottle silver (I still have my silver bottle actually.)