where CeO2-δ was deposited over a Cu foil (Figure ). Thermal NO3RR (sparging dihydrogen into a slurry of catalyst particles) investigations have made similar observations, relating the enhanced activity of Pd/CeO2-δ, relative to Pd/C, Pd/Al2O3, or Pd/SiO2 to the 𝑣 𝑂 •• in CeO2-δ activating the N-O bond of nitrate. The similar voltagedependent rate orders (Figure ) and Tafel slopes (Figure ) for supported Cu and Cu foil suggest the oxide support facilitates the rate limiting step without changing the overall mechanism.