Bimetallic effects on Zn-Cu electrocatalysts enhance activity and selectivity for the conversion of CO2 to CO

Abstract

We report an active zinc-copper (Zn-Cu) bimetallic electrocatalyst for CO 2 reduction to CO, prepared by a facile galvanic procedure. Under moderate overpotentials, Zn-Cu catalysts that are Zn rich exhibit intrinsic activity for CO formation superior to that of pure Zn, Cu, and Ag, the last of which is the state-of-the-art catalyst in CO 2 electrolyzers. Combinatorial experiments involving catalysts prepared by physical vapor deposition reveal trends across the Zn-Cu system, corroborating the high CO selectivity unrivaled by other alloys and intermetallics. Physical and electrochemical characterization and first principles theory reveal that the origin of this synergy in intrinsic activity is an electronic effect from bimetallic Zn-Cu sites that stabilizes the carboxyl intermediate during CO 2 reduction to CO. Furthermore, by integrating Zn-Cu into gas-diffusion electrodes, we demonstrate that bimetallic effects lead to improved electrocatalytic performance at industrially relevant currents. These insights provide catalyst design principles that can guide future development of efficient and earth-abundant CO-producing electrocatalysts. • A Zn-Cu electrocatalyst is prepared by a facile galvanic-exchange synthesis procedure • Zn-Cu electrodes demonstrate high selectivity (>95%) for CO 2 reduction to CO • Bimetallic effects stabilize the carboxyl intermediate during the CO 2 reduction Electrochemical CO 2 reduction is a promising strategy for the sustainable synthesis of fuels and chemicals when combined with carbon-free electricity. A major challenge for the development of electrochemical CO 2 reduction has been establishing robust design principles that can guide the discovery of cost-effective catalysts, due to the complexity of the reaction networks. In this work, we discover a bimetallic effect between Zn and Cu that promotes synergistic performance for CO 2 reduction to CO superior to that of its pure component metals. The insights and catalyst structure-property relationships obtained can guide the future development of efficient and earth-abundant electrocatalysts for CO 2 reduction. We achieve a >7-fold enhancement in intrinsic activity for electrochemical CO 2 reduction relative to a Zn-based electrode, by simply introducing a small quantity of Cu atoms onto the Zn surface. Detailed mechanistic investigations reveal that this improvement originates from a bimetallic effect between Zn and Cu, which can stabilize the key carboxyl intermediate during the CO 2 reduction to CO.