This is very broad subject. There are many reports in the literature about this subject and most of them are recent. There are many types of nanocatalystsl as well as many applications.You have to do a search about this subject to find out which type of research in this field is of interest to you.
Actually this question is very interesting, in my opinion you have to first decide which nanomaterials you want to focus for photocatalytic applications. you may search the applications with Zn based nanomaterials, please look into recent publications with following:
Article ZnO based Nanomaterials for Photocatalytic degradation of Aq...
Article Structure-directing property and growth mechanism induced by...
Article A review on bio-synthesized zinc oxide nanoparticles using p...
Few of others... Check this... Vinaya Satyawan Tari