A reader e-mails:

What this guy did was a fifth-grade science experiment. You can decompose water into hydrogen and oxygen by using copious amounts of electricity. It’s called electrolysis and was discovered around the turn of the last century. What most 12-year-old science-fair entrants do is use a battery to provide the electricity. What this scientist did was to use a solar cell to provide the electricity.
First, thermodynamics require that more energy is require to separate the hydrogen from the oxygen than can be reproduced when they are recombined. Second, even with his new catalyst for the electrolysis step, efficiencies currently available for solar panels (producing oxygen and hydrogen) and fuel cells (recombining them), and even those in the near future, are so low that this is not a viable method.
What I can’t believe is that this guy (a) has been at this for 25 years and this is his result; and (b) has received $4M for what is an elementary school science fair entry.