It is nothing new that scents can influence our mood. They work very directly on our emotional center and that also applies to your cat(s). However, cats do have different scent preferences than humans and it is generally known that cats love the smell of catnip, matatabi and valerian.
Apart from the smell of catnip, which almost no domestic tiger can resist, every cat has its own very personal taste. What is a wonderful smell for one person may be unpleasant for another. Especially with sick or recovering cats, you have to be careful not to confront them with an odor that they find very unpleasant. Therefore, test your cat if he is healthy. This works best with scented cushions.