News items about this work have popped up in several places (like the PV Magazine article referenced above). The chemistry, as described in the popular writeups, doesn't make sense. So I decided to look into it.

Bottom line: the chemistry is valid, but not as described in the popular accounts. The press release from Queensland University of Technology must have been a little sketchy. There's more to it than the evolution of hydrogen and capture of CO2. 

This is essentially the same idea that Dr. Greg Rau, of the UCSC Institute of Marine Sciences, along with collaborators at LLNL and the University of Colorado, has been promoting for several years now. Here's a link to a pretty good writeup about the concept from UC Santa Cruz news center in 2018.

Greg refers to his version of the process as "carbon-negative hydrogen". It exploits the fact that an electrolysis cell produces equal measures of alkalinity at the cathode and acidity at the anode. It's possible to use the acidity from the anode to dissolve silicate minerals, while the alkalinity from the cathode enhances uptake of CO2 from the atmosphere. 

I reviewed some of Greg's papers on the concept several years ago. We were co-members of an interest group on OTEC. My engineering conclusion was that carbon-negative hydrogen would be difficult to commercialize. Ionic solutions are not actually very conductive. Commercial electrolysis cells achieve high productivity by creating a very short flow path between the anode and cathode. Greg's carbon negative hydrogen scheme, however, inherently requires a large volume of electrolyte around the cell anode. It works, but achievable current levels would be at least an order of magnitude too low for commercial utility.

Perhaps the Queensland researchers have found a way around that I was unable to see. I doubt it however. The paper is behind the usual pay wall, and my curiosity about this isn't high enough for me to pony up to read it when I already think I know the answer. Retirement is fun, but having no income kind of sucks.