A very quick Google search gives plenty of info about negative ions. The research is generally positive, but not proven. Just because it doesn't SOUND like science to you, doesn't mean it isn't.
"Once they reach our bloodstream, negative ions are believed to produce biochemical reactions that increase levels of the mood chemical serotonin, helping to alleviate depression, relieve stress, and boost our daytime energy"
A random study, first one I found...
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6213340/ Keep an open mind guys. That's doesn't mean be a new age loony, just understand that there's a huge world of science which you won't have heard of (because you're not a scientist stufying these fields every day) and things yet to be discovered