Can ZnO act as a reducing agent for noble metals like Pd? Palladium ions (e.g., $\ce{Pd^2+}$) can be reduced to $\ce{Pd}$ by more reactive metals such as zinc. Metal oxides such as $\ce{ZnO}$ are very stable but can its atoms in the oxide structure still be displaced by Pd?
I know the answer is probably "No" but in one of my samples $\ce{ZnO}$ nanoparticles were removed from the solution after I added $\ce{Pd^2+}$ solution to the system and $\ce{Pd}$ nanoparticles were formed. The solvent was methanol. After washing the solution and drying I did XPS and no trace of zinc was observed but saw $\ce{Pd}$ peaks.
Zinc chemistry is overwhelmingly that of the +2 oxidation state, it does not go higher. For ZnO to reduce Pd+2, the Zn has to go up from +2 which it cannot. If you are getting reduction of Pd+2, Zn is not responsible.