have you ever attended a conference? Your university should at the very least have informed you of any that are in the area. This can give you a good overview of what is possible in the field.
Other than that you have to make the decision yourself as to what degree of fundamentalism you want in your research. Very basic science, or more applied, or even commercial as in making consumer products.
Physical Chemistry is a very wide field, with applications including (but not limited to!) catalysis, spectroscopy, microscopy, electrochemistry, up to even the more physical aspects in x-ray studies.