Addressing the Carbonate Issue: Electrocatalysts for Acidic CO 2 Reduction Reaction.

Electrochemical CO 2 reduction reaction (CO 2 RR) powered by renewable energy provides a promising route to CO 2 conversion and utilization. However, the widely used neutral/alkaline electrolyte consumes a large amount of CO 2 to produce (bi)carbonate byproducts, leading to significant challenges at the device level, thereby impeding the further deployment of this reaction. Conducting CO 2 RR in acidic electrolytes offers a promising solution to address the "carbonate issue"; however, it presents inherent difficulties due to the competitive hydrogen evolution reaction, necessitating concerted efforts towards advanced catalyst and electrode designs to achieve high selectivity and activity. This review encompasses recent developments of acidic CO 2 RR, from mechanism elucidation to catalyst design and device engineering. We begin by discussing the mechanistic understanding of the reaction pathway, laying the foundation for catalyst design in acidic CO 2 RR. Subsequently, we provide an in-depth analysis of recent advancements in acidic CO 2 RR catalysts, highlighting heterogeneous catalysts, surface immobilized molecular catalysts and catalyst surface enhancement. Furthermore, we summarize the progress made in device-level applications, aiming to develop high-performance acidic CO 2 RR systems. Finally, we outline the existing challenges and future directions in the design of acidic CO 2 RR catalysts, emphasizing the need for improved selectivity, activity, stability, and scalability. This article is protected by copyright. All rights reserved.