Closed-Loop Synthesis of Highly Dispersed Cobalt Phthalocyanine Catalysts for Efficient CO₂ Electroreduction

Abstract

Electrochemical CO 2 reduction offers a promising path to transform excessively emitted CO 2 into valuable products. However, the lack of sustainable access to effective catalysts hampers the practical applications of this important process. Herein, we report a closed-loop synthesis strategy to fabricate a type of hybrid catalysts based on multiple-round adsorption of cobalt phthalocyanine onto carbon black from a dilute solution. This strategy allows for recycling and reuse of all the reagents involved in the synthesis, which not only minimizes the waste production but also reduces the catalyst cost significantly. Furthermore, the strategy enables catalyst synthesis at gram scale with remarkable reproducibility and is universal for catalyst synthesis starting from metal phthalocyanines with different functional groups. More importantly, we show that it is possible to integrate the preparation of effective hybrid catalysts with the elimination of metal phthalocyanine pollutants from wastewater. Benefiting from the highly dispersed cobalt sites, the hybrid catalysts exhibit good performance for electrochemical CO 2 reduction. Specifically, a large current density of 250 mA cm −2 , a high Faradaic efficiency of 99%, and an excellent turnover frequency of 2.0 × 10 5 h −1 for CO production can be achieved in the flow cell. This study demonstrates the great potential of the closed-loop strategy for sustainable, scalable, and cost-effective synthesis of efficient catalysts for CO 2 valorization, contributing to the mitigation of climate change.