There is a certification, but it is a general knowledge test of the specialty area and the recommendation is that you have 2 years experience in the specialty before taking the exam. You can find information about it here:
http://www.nbchpn.org/
Oncology, geriatrics, med-surg, and long-term care all offer aspects of the body of experience that will help you if you decide to enter hospice/palliative nursing in the future. Best wishes for success in your studies.