Not without large amounts of waste energy. This energy cost makes electrolysis impractical for efficient energy storage.

If you could reduce the amount of energy required to electrolyze water, then it would make an extremely good energy storage vehicle. That's exactly what this research is about.

Releasing or not releasing O2 has nothing whatsoever to do with waste energy. It's impossible to electrolyze water without releasing O2.

It's great to try to make it more efficient, but this research doesn't actually do that, it just makes the equipment cheaper, but at the same efficiency.

And besides electrolysis is a terrible way to store energy because storing hydrogen is impractical (it leaks right though metal). Plus there are unavoidable inefficiencies.