In-situ Scanning Tunneling Microscopy of Cobalt Phthalocyanine Catalyzed CO2 Reduction Reaction.

We report a molecular investigation of cobalt phthalocyanine (CoPc) catalyzed CO 2 reduction reaction by electrochemical scanning tunneling microscopy (ECSTM). An ordered adlayer of CoPc is prepared on Au(111). Approximately 14% of the adsorbed species appear with high contrast in CO 2 purged electrolyte environment. The ECSTM experiments indicate the proportion of high contrast species correlated with the reduction of Co II Pc (~-0.2 V). The high contrast species is ascribed to CoPc-CO 2 complex, which is further confirmed by theoretical simulation. T he sharp contrast change from CoPc-CO 2 to CoPc is revealed by  in situ ECSTM in the reaction. Potential step experiments provide dynamic information for the initial stage of the reaction, which including the reduction of CoPc and the binding of CO 2 , and latter is the rate-limiting step. The rate constant of the formation and dissociation of CoPc-CO 2 is estimated on the basis of the in situ ECSTM experiment.