Hi Bm6
Thank you for your request.
You can buy the Half Fare Travelcard at Zurich Airport and use it immediately. You can also pay by cash. You’ll receive a transitory SwissPass. We need your passport/ID card and a photo of you. There will be a possibility to transmit the photo also within a link when you are at the train station. There’s no other documentation needed.
I wish you a nice day.
Kind regards, LeaG