Identifying the optimal oxidation state of Cu for electrocatalytic reduction of CO2 to C2+ products

Abstract

The electrocatalytic CO₂ reduction reaction (CO₂RR) to C₂₊ products is of great importance. It is known that the co-operation of Cu¹⁺ and Cu⁰ in the catalysts can yield a high faradaic efficiency (FE). However, it is very difficult to figure out the optimal ratio of Cu¹⁺ and Cu⁰ because Cu¹⁺ can be reduced to Cu⁰ during CO₂RR. To solve this problem and identify the optimal oxidation state of Cu, herein we propose a strategy to prepare Cu catalysts with different oxidation states, which could be stabilized by the pulsed electrolysis method during CO₂RR. On the basis of this method, we have studied the effect of the oxidation state of Cu on CO₂RR to form C₂₊ products. It has been found that the Cu catalyst with an oxidation state of +0.41 is the most efficient in our reaction system, and the FE of C₂₊ products is 70.3% in an H-type cell. This work provides a precise method to identify the optimal oxidation state of the catalysts that are not stable in the reaction.