From Sydney to Japan (stop over in Beijing for 8 hours)

Hi! I'm from Brazil but I live in Australia and I'm going to Japan from Sydney, stopping over in Beijing for 8 hours. My passport is Brazilian, but I have Australian visa. My question is: do I need to apply for the 24h direct transit in Beijing, at the airport in Sydney before landing or can I just do it at the airport in Beijing?

Thanks!
Maryana