Hierachical Aerogel-Supported Cu-Sn-O x Solid Solutions for Highly Selective CO 2 Electroreduction and Zn-CO 2 Batteries.

The electrochemical CO 2 reduction reaction (CO 2 RR) into high-value carbon compounds such as CO and HCOOH is a promising strategy for the utilization and conversion of emitted CO 2 . However, the selectivity of the CO 2 RR for HCOOH is typically less than 90% and operates within a narrow voltage range, which limits its practical application. Herein, we propose a novel heterostructural aerogel as a highly efficient electrocatalyst for CO 2 RR to HCOOH. This catalyst consists of Cu-Sn-O x solid solutions embedded in a reduced graphene oxide matrix (Cu-Sn-O x /rGO). The incorporation of Cu 2+ into the SnO 2 matrix enhances HCOOH production by improving the adsorption of the *OCHO intermediate and inhibiting H 2 evolution, as confirmed by in situ measurements and computational studies. As a result, Cu-Sn-O x /rGO achieves a remarkable Faradaic efficiency (FE) of up to 91.4% for HCOOH and maintains high selectivity over a broad operating voltage range (-0.8 to -1.1 V). Additionally, the assembled Zn-CO 2 batteries demonstrated an excellent power density of 1.14 mW/cm 2 and exceptional stability for over 25 h.