حَمْدًا
Translation: I offer praise.
حَمْدًا: accusative maṣdar of an unspoken verb.
Expanded: حَمِدْتُكَ حَمْدًا; the finite verb has attached subject tāʾ, -ka is object, ḥamdan absolute object.
Shukran centers gratitude; ḥamdan centers praise. They should not be treated as semantically identical.