I will be arriving 13 July from NRT with US passport, then leaving PVG 2days later 15 July to USA

I have a a standby ticket leaving China. But since I will only be in Shanghai for 2 days am I eligible for this 144-hour rule? Or must I pay for any China Visa on arrival or will I be required to hold a tourist China Visa if I have a standby ticket to leave flight?