For safety reasons, the OneBlade is designed to only work cordless.
This is because the Philips OneBlade can be used for both wet and dry shaving. Using it with water while connected to electricity can be very dangerous. To avoid any risks, the appliance does not work while it is connected to a power outlet.
Also keep in mind that the adapter for OneBlade is not waterproof. Hence, while charging your OneBlade, make sure that you keep it and its adapter away from water or any wet surface.