Tunable Selectivity and High Efficiency of CO(2) Electroreduction via Borate-Enhanced Molten Salt Electrolysis

Converting CO(2) into value-added chemical fuels and functional materials by CO(2) reduction reaction (CO(2)RR) is conducive to achieving a carbon-neutral energy cycle. However, it is still challenging to efficiently navigate CO(2)RR toward desirable products. Herein, we report a facile strategy to extend product species in borate-containing molten electrolyte at a positively shifted cathodic potential with a high current density (e.g. 100 mA/cm(2)), which can selectively electro-transform CO(2) into desired products (either CO or solid carbon nanofibers, respectively reaching a high selectivity of ∼90%). The borates can act as a controller of electrolyte alkalinity to buffer the concentration of sequentially generated O(2−) during CO(2)RR, positively shifting the reduction potential of the captured CO(2) and concurrently extending the product species. The sustainable buffering effect is available under CO(2) atmosphere. Compared with borate-free electrolyte, the CO(2) conversion efficiency is over three times higher, while the electrolysis energy consumption is decreased by over 40%.