One day trip to Shenzen from Hong Kong

No, you cannot use 24 hour visa free transit, but the solution is very simple. You will arrive with MTR at Lo Wu (Luohu) border crossing where you will apply for a 5 days Shenzhen visa on arrival. It costs just 130 CNY and you will pay for it by your card. After your stay in Shenzhen you can return by taking any border crossing and any mean of transport, high speed train included. Of course, you can return via the same border crossing and use MTR again. You should be at Lo Wu (Luohu) border crossing the latest at 08:30, just before the opening of Luohu visa office in order to avoid the major queues. Have a nice visit to Shenzhen.