Hierachical Aerogel-Supported Cu–Sn–Ox Solid Solutions for Highly Selective CO₂ Electroreduction and Zn–CO₂ Batteries

The electrochemical CO2 reduction reaction (CO2RR) into high-value carbon compounds such as CO and HCOOH is a promising strategy for the utilization and conversion of emitted CO2. However, the selectivity of the CO2RR 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 CO2RR to HCOOH. This catalyst consists of Cu–Sn–Ox solid solutions embedded in a reduced graphene oxide matrix (Cu–Sn–Ox/rGO). The incorporation of Cu2+ into the SnO2 matrix enhances HCOOH production by improving the adsorption of the *OCHO intermediate and inhibiting H2 evolution, as confirmed by in situ measurements and computational studies. As a result, Cu–Sn–Ox/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–CO2 batteries demonstrated an excellent power density of 1.14 mW/cm2 and exceptional stability for over 25 h.