Phase Engineering of a Tin Oxide-Based Nanostructured Catalyst for Efficient Electrochemical Reduction of CO ₂ toward Formate

Although Sn-based materials have been widely investigated for formate-producing CO 2 RR catalysts because of their abundance and high formate selectivity, tremendous challenges remain in developing highly efficient and stable Sn-based catalysts for CO 2 electrolysis under industrially relevant conditions. This work proposes an in situ approach to engineering the tin oxide phase to enhance the activity and stability of the material. In this study, nanostructured Sn-based catalysts were synthesized from SnCl 2 via a one-pot hydrothermal reaction. Electrochemical, chemical, and morphological properties were characterized to elucidate the synthesis process, the CO 2 RR-to-formate electrocatalytic activity, and the catalyst stability under prolonged electrolysis. The results reveal that an optimal reaction time of only 4 h yields an effective SnO x catalyst with a good formate Faradaic efficiency of 87.1% at a high current density of 200 mA cm –2, originating from a defective, oxygen-vacancy-rich surface induced by mixed oxidation states of Sn. Although concerns about catalyst durability persist, the rapid, cost-effective, and facile method introduced in this research offers a practical pathway to fabricating an effective SnO x catalyst for CO 2 RR.