CV of supported Cu catalysts (Cu/FTO and Cu/CeO2-δ) demonstrate qualitatively similar behavior for NO3RR as Cu foil (Figure ,b). A cathodic limit of -0.6 VRHE was chosen for supported catalysts to prevent cathodic dissolution of FTO. In the absence of nitrate, the only Faradaic process on Cu/CeO2-δ corresponds to phosphate deprotonation, evident by ca.