Gallium modulated tin oxide for continuous production of formic acid via durable acidic CO₂ electroreduction

CO₂ reduction catalyst corrosion and H₂ evolution remain challenging under the strongly acidic electrolyte. Here, Ga-modulated SnO_x was investigated to achieve a good Sn^δ+ oxidation state stability for durable (> 4000 hours) acidic CO₂ reduction to HCOOH. Under pH 1.7, catalysts achieved a partial current density of 440 mA cm^-2 at -1.63 V_RHE and the highest single-pass conversion efficiency (SPCE) of 91.9%. In a 10 cm² electrolyzer, a total current of ~986.3 milliampere is exhibited for more than 4000 hours with Faradaic efficiency of HCOOH (FE_HCOOH) higher than 82% and SPCE higher than 50%. Mechanism study indicates that lattice oxygen anchoring effect of Ga due to its strong oxygen affinity establishes a stable framework, reinforcing interface Sn─O bonds and protecting the Sn^δ+ from the heavy self-reduction process. The robust structure of catalyst and modulated active Sn^δ+ sites elevate the CO₂ reduction activity. The durable and highly efficient catalytic system exhibits the potential for industrial applications of the Ga-modulated SnO_x.