Morphologically engineered S-InxZny bimetallic catalysts via an ionothermal approach for enhanced carbon dioxide electroreduction to formate†

The conversion of carbon dioxide through electrochemical reduction (ECO₂RR) offers a promising pathway for sustainable carbon cycling, yet the development of efficient catalysts remains challenged by the trade-off between activity and stability. Herein, we report a sulfur-modulated In–Zn bimetallic sulfide catalyst (S-In_0.5Zn₁) that achieves highly selective CO₂-to-formate conversion via morphological engineering. The optimized catalyst demonstrates exceptional performance with a maximum formate faradaic efficiency (FE) of 95.2% at −1.36 V vs. RHE, coupled with outstanding long-term stability exceeding 80 hours. Systematic investigations reveal that Zn incorporation induces a microstructural reconstruction, forming a hierarchical nanoparticle-lamellar composite architecture. This unique morphology significantly enhances the specific surface area and establishes efficient mass transport pathways, effectively mitigating diffusion limitations for both CO₂ reactants and critical *OCHO intermediates during electrocatalysis. The resultant reduction in kinetic barriers substantially improves the conversion efficiency of formate production. The findings not only introduce a metal sulfide catalyst system combining high activity and stability for ECO₂RR but also provide fundamental structural insights for the rational design of advanced CO₂ conversion electrocatalysts.