Are psn cd keys region free? If not where can I get one in my region?

I live in China, and I have a PS4, for some reason, I can't buy anything with credit cards in playstation store, so I was thinking if I could use psn cd keys - https://www.scdkey.com/playstation-prepaid-card_5.html  to purchase in playstation store. Where can I get one for my area?