Oxygen Vacancy-Induced and Boundary Effects Promote Electrochemical CO₂ Reduction to Formic Acid under Acid Electrolytes

Electrochemical CO2 reduction reaction (eCO2RR) is a meaningful way for CO2 depletion and value addition. And electrocatalysts play great roles in the CO2 reduction product selectivity. SnOx-based catalysts have been widely used in formate production. However, the activity and selectivity are still unsatisfying, especially at the industrial level current density (>0.2 A cm–2) for pure HCOOH production. In this work, we proposed a triple-metal composite electrocatalyst with high oxygen vacancy contents and an abundant grain-boundary strategy for the eCO2RR. In particular, oxygen vacancies in the designed catalyst reached 13.9%. When catalysts were employed as catalysts for eCO2RR, both high HCOOH FE and long-term electrolysis stability under acid electrolytes were obtained. The FE of HCOOH was around 87.9% at 0.3 A cm–2 and was stable even after 15,000 s of electrolysis. This work provides a new path for electrocatalyst design and highly efficient HCOOH production.