Modulating CO2 electroreduction to syngas by protic-nonprotic ionic liquid composite electrolytes

CO2 electroreduction reaction (CO2RR) to syngas with a tunable CO/H2 ratio and high current density is a promising but challenging application. Here, we report a novel electrolyte, including nonprotic IL acetonitrile (MeCN), [Bmim][NTf2], and protic IL [Bim][NTf2] for CO2RR to syngas. When the concentration of [Bim][NTf2] increased from 0.005 to 0.12 mol·L−1, the CO/H2 ratio dropped from 30 to 0.1 and the current density increased from 26.4 to 113.4 mA·cm−2 at −2.3 V vs. Ag/Ag+ in H-cell. The [Bim][NTf2] not only can generate H+ to accelerate HER, but also increases the CO2 solubility to promote CO2RR to CO. Meanwhile, the [Bmim][NTf2] mainly increased the current density for CO2RR. By varying the concentration of [Bim][NTf2], the CO/H2 ratio could be modulated in ternary electrolyte. This work offers a novel method to modulate the CO/H2 ratio for enhancing the efficiency of CO2RR to syngas with a high current density in H-cell.