Abstract: Earth-abundant and nontoxic Sn-based materials have been regarded as promising catalysts for the electrochemical conversion of CO₂ to C1 products, e.g., CO and formate. However, it is still difficult for Sn-based materials to obtain satisfactory performance at low-to-moderate overpotentials. Herein, a simple and facile electrospinning technique is utilized to prepare a composite of a bimetallic Sn-Co oxide/carbon matrix with a hollow nanotube structure (SnCo-HNT). SnCo-HNT can maintain > 90 % faradaic efficiencies for C1 products within a wide potential range from - 0.6 V_RHE to - 1.2 V_RHE, and a highest 94.1 % selectivity towards CO in an H-type cell. Moreover, a 91.2 % faradaic efficiency with a 241.3 mA cm^-2 partial current density for C1 products could be achieved using a flow cell. According to theoretical calculations, the fusing of Sn/Co oxides on the carbon matrix accelerates electron transfer at the atomic level, causing electron deficiency of Sn centers and reversible variation between Co²⁺ and Co³⁺ centers. The synergistic effect of the Sn/Co composition improves the electron affinity of the catalyst surface, which is conducive to the adsorption and stabilization of key intermediates and eventually increases the catalytic activity in CO₂ electroreduction. This study could provide a new strategy for the construction of oxide-derived catalysts for CO₂ electroreduction.

Key words: Hierarchic structure, Tin-cobalt bimetallic oxide, Electronic effect, CO₂ electroreduction, Wide potential range