An Energy-Efficient Integrated System by Coupling Carbon Dioxide Reduction and Methanol Oxidation to Produce the Identical Value-Added Formic Acid

Abstract

Metal-organic frameworks (MOFs) are considered as promising catalytic materials for electrochemical carbon dioxide reduction (ECR) reactions due to their excellent properties. However, the development of efficient and stable electrocatalysts within a wide potential window remains a great challenge. Herein, the rod-like Sn-MOF is synthesized by a fast and simple solution reaction, which has good performance in converting CO2 to HCOOH. In particular, Sn-MOF reaches a maximum Faradaic efficiency of 86.4% at −1.15 V vs RHE with a current density of 25.2 mA cm−2. It is worth noting that Sn-MOF has excellent long-term stability, maintaining more than 80% of FEHCOOH production within 30 h of continuous electrolysis. Meanwhile, X-ray diffraction and X-ray photoelectron spectroscopy characterization confirm that Sn2+ in Sn-MOF can be reduced to Sn0 in the ECR reaction. The theoretical results show that *COOH intermediate tends to form in the ECR process on Sn-MOF, and it has a high selectivity for the formation of HCOOH. In addition, the two-electrode system driving the co-electrolysis of methanol and CO2 can significantly reduce the voltage by 500 mV at a current density of 20 mA cm−2.