19 hour layover in Beijing to Bangkok

Hello
I have a 19 hour layover in Beijing from USA to Bangkok. My airline carrier is AirChina who is also offering a free night stay at local hotel (outside airport -PEK). I plan to venture the city and continue my travel to Bangkok via Beijing.

My questions are:
(a) Am I still required to apply/purchase a visa?
(b) If not, how do I apply for a free 72-hour free transit since my time in China (PEK) is less than 24 hours?

Thank you
(b)