You could look into buying lion poop/manure, it's for this reason and helps fertilise the ground. I've had some success with cat deterant granules from amazon but every cat is different.

Putting down old coffee grounds or citrus peel are often given as suggestions too. Planting lavender and peppermint plants - a lot of cats don't like the smell, some wont give a fk.

Big problem is this looks and feels like a litter tray to cats.

You could make the soil suitable for cactus, there is also little plastic spikey mesh things to put down that deters cats and dogs no harm just uncomfortable.

Oh also large chunky gravel, not the little stuff but the ones that look like rocks, they can't dig it and its uncomfortable to walk on - although you'll probably get the odd weirdo that still poops on top of it.