Chemically coupling SnO2 quantum dots and MXene for efficient CO2 electroreduction to formate and Zn-CO2 battery

Electrochemical conversion of CO2 into formate is a promising strategy for mitigating the energy and environmental crisis, but simultaneously achieving high selectivity and activity of electrocatalysts remains challenging. Here, we report low-dimensional SnO2 quantum dots chemically coupled with ultrathin Ti(3)C(2)Tx MXene nanosheets (SnO2/ MXene) that boost the CO2 conversion. The coupling structure is well visualized and verified by high-resolution electron tomography together with nanoscale scanning transmission X-ray microscopy and ptychography imaging. The catalyst achieves a large partial current density of -57.8 mA cm(-2) and high Faradaic efficiency of 94% for for-mate formation. Additionally, the SnO2/MXene cathode shows excellent Zn-CO2 bat-tery performance, with a maximum power density of 4.28 mW cm(-2), an open-circuit voltage of 0.83 V, and superior rechargeability of 60 h. In situ X-ray absorption spec-troscopy analysis and first-principles calculations reveal that this remarkable perfor-mance is attributed to the unique and stable structure of the SnO2/MXene, which can significantly reduce the reaction energy of CO2 hydrogenation to formate by increasing the surface coverage of adsorbed hydrogen.

Automated summary

This study reports a chemically coupled catalyst of low-dimensional SnO2 quantum dots and MXene nanosheets that enhances the conversion of carbon dioxide and shows excellent performance in battery applications.