I want to report one of my co-workers to human resources for not wearing shoes in the workplace.
Why do you want to report your co-worker to human resources for not wearing shoes?
Because it's unsanitary and not professional for a business environment.
I'm sure your co-worker's behavior is bothering you and it's good that you reported them to human resources. It's not appropriate for your co-worker to not follow the rules and dress that appropriate for a business environment.
Doesn't help that their feet smell as well.
That certainly isn't right for a professional setting like the work office. Good on you for calling them out.