Tunable Selectivity and High Efficiency of CO Electroreduction via Borate-Enhanced Molten Salt Electrolysis.

Converting CO into value-added chemical fuels and functional materials by CO reduction reaction (CORR) is conducive to achieving a carbon-neutral energy cycle. However, it is still challenging to efficiently navigate CORR 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), which can selectively electro-transform CO 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 during CORR, positively shifting the reduction potential of the captured CO and concurrently extending the product species. The sustainable buffering effect is available under CO atmosphere. Compared with borate-free electrolyte, the CO conversion efficiency is over three times higher, while the electrolysis energy consumption is decreased by over 40%.