Wrapping Tin Sulfide Nanocatalysts with Graphene Oxide Nanosheets for Improved Electroreduction of Carbon Dioxide to Formic Acid

Electroreduction of carbon dioxide (CO₂) to formic acid is an important piece of puzzle in carbon neutralization and modern chemical industry. However, the catalytic activity and selectivity of this reaction still need to be improved for practical applications. Herein, we reveal that a highly active, selective, and stable electroreduction of CO₂ to formic acid could be realized by wrapping tin sulfide (SnS_x) nanoparticles with graphene oxide (GO) nanosheets. The GO wrapping helps to preserve the crystal size of SnS_x (2∼4 nm) and confine the sulfur atoms in SnS_x, obtaining a promising catalyst. As a result, a high current density of 126.25 ± 0.78 mA cm^-2 and high Faradaic efficiency (FE) of 99.9 ± 1.1% toward formic acid is achieved in a flow cell. The current density could be further improved to 554.41 ± 2.32 mA cm^-2 in a membrane electrolyzer. Additionally, our catalytic system demonstrates a high stability exceeding 50 h at ampere-level current. This finding provides a valuable insight for further development of highly efficient and selective catalysts for electroreduction of CO₂ to high-value carbon-containing products. Our strategy may also be applied to preserve the structures of many other amorphous or nanocrystal catalysts for efficient and stable electrocatalysis.