Electric control of the chemical reaction in ceramic-ceramic contact interface - modeling of the reaction scheme

The CuO/ZnO heterocontact is made by stacking CuO and ZnO porous ceramics and its catalytic activity for CO oxidation reaction is evaluated as a function of applied bias. Its catalytic activity is strongly depend on the dc applied bias and when the reverse bias (CuO^-, ZnO⁺) is applied to the heterocontact, the amount of the produced CO₂ from the catalytic interface rapidly increases, while it decreases when forward bias is applied. The magnitude of the enhancement of the catalytic activity by reverse applied bias is extremely large (30% for -2.0 V at 320 °C), comparing with the results in the gradient composition CuO/ZnO heterocontact. The p-i-n structure is suggested as to the electronic structure of the CuO-ZnO contact interfaces and supposing p-i-n structure, the surface Fermi level position of CuO and ZnO are guessed to move as a function of applied bias. The catalytic reaction over CuO make a large contribute to the whole catalytic reaction at the CuO/ZnO heterocontact and it would be modified by the applied voltage dependent surface Fermi level position of CuO. The working mechanisms of such phenomena are qualitatively discussed by the electronic theory of catalyst proposed by Wolkenstein.