On our return trip back home (Toronto), we plan to fly from Hong Kong to Shanghai

on Dec 28, leave the Shanghai Airport, stay one night in a hotel near the airport, and then the next day Dec 29 departing from Shanghai to Toronto. I assume this 72-hour visa-free transit applies to us. Do we have to show any documents (hotel receipts, airline tickets) to the custom officers in Hong Kong on Dec 28, and in Shanghai on Dec 29?