In a study published in The Innovation, Prof. WEI Wei, Prof. CHEN Wei and Prof. SONG Yanfang from Shanghai Advanced Research Institute of the Chinese Academy of Sciences constructed a hierarchical SnO₂(101)@Ni composite hollow-fiber penetration electrode (HPE), which helped to realize high-efficiency CO₂ electroreduction to formate in neutral electrolyte at ampere-level.

The electrochemical CO₂ reduction reaction (eCO₂RR), powered by renewable energy, is a promising method for converting CO₂ into value-added products, thereby enabling sustainable carbon-neutral cycles. However, the practical implementation of eCO₂RR technology is challenged by limitations in activity, selectivity, and stability.

To simultaneously achieve high formate Faradaic efficiency, high current density, and long-term stability, researchers constructed facet-oriented SnO₂ nanoflowers arrayed on the exterior of three-dimensional nickel hollow fibers by a facile hydrothermal method.

This electrode demonstrates exceptional electrocatalytic performance for converting CO₂ to formate.A formate selectivity of 94% and stability of 300 h with a current density of 1.3 A cm^-2 at −1.1 V (vs. RHE) are attained under ambient conditions. Notably, an extremely high CO₂single-pass conversion rate of 85% is achieved, outperforming prominent catalysts reported in electrocatalysis.

The synergetic combination of the unique nanostructures and their advanced spatial configuration is proposed to be responsible for the facet-oriented SnO₂ with a hierarchical structure, providing fully exposed active sites and facilitating mass and charge transfers. Enhanced mass transfer in the hollow fiber electrode verified by electrochemical measurements and well-retained Sn⁴⁺species confirmed by in situ spectroscopy synergistically boost the high CO₂conversion activity. In situ spectroscopy and theoretical calculation results demonstrate that theSnO₂(101) facet favors *OCHO intermediate formation and *HCOOH desorption, leading to high formate selectivity.

This study provides a straightforward approach to the precise fabrication of composite hollow fiber electrodes, enabling highly efficient electrocatalytic reactions with gas molecules.

Schematic diagram of electroreduction of CO₂ to formate over SnO₂@Ni hollow fiber penetration electrode (Image by SARI)