Tunable Selectivity and High Efficiency of CO2 Electroreduction via Borate-Enhanced Molten Salt Electrolysis

Abstract

Summary 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%.

Synthetic strategies for MOF-based single-atom catalysts for photo- and electro-catalytic CO2 reduction

“…Carbon dioxide is a relatively stable molecule, and the initial activation of carbon dioxide is often a key step in the reduction of carbon dioxide (Handoko et al, 2020;Hu et al, 2020). The initial activation of carbon dioxide in electrocatalytic reduction may go through the following three paths (Quan et al, 2021).…”

Capture and electrochemical conversion of CO2 in molten alkali metal borate–carbonate blends

“…Electrolytic production of carbon nanotubes using molten lithium carbonate compositions can be aided or mediated by the addition of small quantities of metaborates. 30,31 Adding lithium metaborate (LiBO 2 ) into molten LiCl–Li 2 CO 3 electrolyte at metaborate concentrations up to 1–2 wt% can thermodynamically change the reaction pathway, accelerating the electrolysis and enabling formation of the CO 2 -derived products such as CO or CNT at lower cell voltages. 30–32…”

CO2 Electroreduction in Organic Aprotic Solvents: A Mini Review

“…Among them, the most studied are ionic liquids [19][20][21][22][23][24][25][26], methanol solutions [27][28][29], and organic aprotic solvents [30][31][32][33][34][35][36][37][38][39][40]. In recent years, there has also been engagement in the CO 2 electrochemical reduction process in molten salts [41][42][43][44][45][46]. e following valuable nanomaterials can be obtained in such an environment: carbon nanofibers [43], carbon nanotubes (CNTs), carbon spheres (CSs), and honeycomb carbon [44].…”

“…In recent years, there has also been engagement in the CO 2 electrochemical reduction process in molten salts [41][42][43][44][45][46]. e following valuable nanomaterials can be obtained in such an environment: carbon nanofibers [43], carbon nanotubes (CNTs), carbon spheres (CSs), and honeycomb carbon [44]. In addition, the simplicity of the design of the diaphragm-free electrolyzer (Figure 4), high conversion speed (i cathode = 100 mA × cm − 2 ), and high Faradaic efficiency (80-90%) of products [42] make this method promising.…”