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

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