Yes, you can without issue.
Make sure when you download Alipay you select International region and not Mainland China. Then you’ll be able to add RMB to your Alipay account using your Monzo card within the Alipay app. Keep in mind you’ll need to verify your identity and it’s a temporary service - it’s not designed to be used permanently.
If you’re a Chinese national you cannot use this option and you’ll instead need to use Transferwise, a similar service or another bank to send money directly to a Chinese bank account.