Can I purchase the Hutong card in Daxing Airport ?

I'm afraid no, you need to go to the service center at Dongzhimen to consult about the card with your passport.

Try to buy the card at the Daxing Airport Station service desk first. If it fails, then go to Caoqiao Station. Try Line 19 Station service desk to buy one. If nobody there, then go out of Caoqiao Station either E1 or E2 Exit. Turn on Chinese Map App. Find direction to Caoqiao Bus Stop by entering keyword "caoqiao". There is a big bus depot of Beijing City Bus about 2 kilometers away from Caoqiao Subway Station. The map app should direct you to "玉泉营桥南" Yuquanyingqiaonan bus stop to take bus 679 or 497. Caoqiao bus stop is the first stop from Yuquanyingqiaonan. After arriving at Caoqiao bus stop, then go up overhead pedestrain bridge to go across the street. Turn right toward the entrance of the bus depot. There is a service shop dealing Yikatong card. Say "E Ka Tong E go" to buy one. If even they refuse to sell, your luck is over for the day. Go to your hotel.