When connected to Dex station, Can I charge my S8|S8+?

You can use the Samsung DeX multimedia dock only when you connect it to a charger and need to use only Samsung-approved chargers(9 V/1.67 A, 9 V/2 A, 12 V/2.1 A). Charging device connected to Samsung DeX station may not work properly depending on the type of connected charger.
For example, if you want fast charging of S8/S8+ device while connecting with DeX Station, use only Samsung-approved chargers that support fast charging based on *12V/2.1 A

Note: These are the chargers supplied for Samsung Tablet devices

And, if Samsung DeX station is connected to Samsung-approved Adaptive Fast Charger for general smartphones, fast charging does not operate and general charging is only possible. However, charging itself is not supported if Samsung DeX station is connected to the standard Samsung-approved charger, not Samsung Adaptive Fast Charger..