Electrochemical CO 2 Reduction Catalysed by Cobalt Octacyanophthalocyanine and its Mechanism

Electrochemical CO 2 reduction was studied by using a graphite electrode coated with cobalt octacyanophthalocyanine ( CoPc ( CN )8) and dipped in an aqueous phase. The most active and selective CO 2 reduction was achieved at −1.20 V (vs Ag / AgCl ) with the ratio of the produced CO / H 2 around 10 at pH 9.3. The electrocatalytic CO 2 reduction by CoPc ( CN )8 could be achieved at a more positive applied potential than non-substituted CoPc ( CoPc ), which can be ascribed to the relatively positive redox potential of CoPc ( CN )8. The catalytic mechanism of the CoPc ( CN )8 in a homogeneous system was investigated by an in situ potential-step chronoamperospectroscopy under argon and under CO 2 as well. In CoPc ( CN )8 the rate-determining step was an intermediate formation step, while in CoPc it was the second reduction of the complex.