Cu-Doped Highly Porous SnO2 for Long-Lasting Acidic CO2 Electroreduction at 1000 mA cm–2

Abstract Electrochemical CO2 reduction reaction (CO2RR) to formic acid (HCOOH) provides a carbon-neutral route. SnO2-based catalysts suffer from limited activity and instability at industrial current densities. We develop a Cu-doped highly porous SnO2 catalyst (SnO2-Cu) that enhances activity and stabilizes the SnO2 framework. The porous structure exposes numerous active sites while confining local OH– within the bulk acid electrolyte, enabling high-current-density operation. Cu doping strengthens CO2 chemisorption and Sn–O bond covalency, boosting CO2RR activity while suppressing SnO2 self-reduction. SnO2-Cu sustains 1000 mA cm–2 for 19 h with 98.5% FE and 800 mA cm–2 for 72 h with 94.1% FE in a flow cell at pH 1.82. It achieves a HCOOH production cost of 722.7 USD tonne–1 in a solid-state electrolyte (SSE) device calculated based on onshore wind power, demonstrating economic competitiveness. This work demonstrates that rational Cu doping of porous SnO2 addresses activity and durability limits, offering an effective platform for high-rate, economically viable HCOOH electrosynthesis.