Boosting Electrocatalytic CO2 Reduction with Conjugated Bimetallic Co/Zn Polyphthalocyanine Frameworks

Development of high-efficiency electrode materials for the electrochemical CO2 reduction reaction (CO2RR) with high current density and selectivity compatible with industry is an important but significant challenge. Herein, we describe a facile strategy to enhance the selectivity and current density by regulating the local electron density of the cobalt site in a series of stable, conjugated, bimetallic Co/Zn polyphthalocyanine frameworks CoxZnyPPc with an AB stacking model under alkaline aqueous conditions. When adjusting the ratio of Co and Zn to 3:1, the optimal Co3Zn1PPc exhibits an industry-compatible CO partial current density of 212 mA cm(-2) at -0.9 V versus reversible hydrogen electrode in a flow cell, which is 1.7 and 9.1 times that of the single metal polyphthalocyanine CoPPc and ZnPPc, respectively. Co3Zn1PPc shows a high CO Faraday efficiency of more than 90% in a wide operating potential window of -0.3 to -0.9 V. In-depth experimental and theoretical analysis revealed that introduction of electron-rich Zn atoms modified the electron density of the active Co center, placing Co in the electronrich region and weakening the bonding strength with the reaction intermediate, thereby improving the CO2RR performance. These results clarify the interaction mechanism of dual metal sites at the atomic level and provide a new avenue for the design of electrocatalysts with potential in industrial applications.