Network cards are said to work on layer 2 (Datalink - Mac Address), but you can also argue that they also work on layer 1 (Physical) as they contain the jack where the network cable and electrical signals terminate (or are generated when transmitting).
The NIC card is a Layer 1 device because it sends data over physical media such as a CAT5 cable.
The NIC card is a Layer 2 device because there are two sub layers on Layer 2. The Logical Link Control (LLC) and Media Access Control (MAC). The MAC sub layer communicates with hardware such as NIC cards by using their MAC addresses