Yes. It would work as a pass-through charging pad when you use it. It will charge the devices connected to it first, and will automatically switch to recharge itself when the external devices are fully charged. 

However, in this mode, the charging voltage may be low when the battery of the power bank is low depending on the AC adapter that you use. For best results, the adapter should be able to support 2A current at 5V. If the power bank does not charge your phone, press the power button on the power bank once to switch from charging the internal battery to charging the external device.