Early in the war there have been discussions about this and the rumblings were that Russia wanted to use tactical nukes on the battlefield, but China said "no".

https://www.newsweek.com/china-news-reacts-after-russia-chan...

Apparently they still regularly do: https://www.politico.eu/article/volodymyr-zelenskyy-china-ur...

I am happy that some cooler heads prevail.