"The researchers also plan to develop a water splitter than runs on electricity produced by solar energy."
Unfortunately that approach would be less efficient that simply transferring the electrical energy to an electric motor.
Light > Electricity > Hydrogen > Electricity > Electric Motor
is longer than
Light > Electricity > Electric Motor
Did you do that when you were 9 too?
That may have been coincidence but it certainly wasn't new knowledge to me that Nickel works well as an electrode when splitting water in Hydrogen and Oxygen.
I wished I'd kept my books from childhood and I'd be able to show you. It wasn't a particular fancy set either, just a bunch of test tubes, some leads to attach to a 4.5 V flat battery (I haven't seen those in ages either) and a bunch of basic chemicals.
Using non-mobile solar cells to produce an energy-dense fuel which is portable makes sense, even if there is an efficiency hit.
Cars themselves are not efficient no matter how they are powered, because utmost efficiency in a car means lying on your back in a narrow, feather-weight, fragile aerodynamic tube with wheels, going about 25 mph max, and taking minutes to get to that speed. Forget niceties like air conditioning.