A pH-differential dual-electrolyte microfluidic electrochemical cells for CO2 utilization

• Advancing CO2 electrochemical reduction via thermodynamic approach based on microfluidics.
• pH-differential technique enhances the thermodynamic properties of electrodes.
• Individual electrode potentials move closer to the equilibrium status.
• Reactivity and efficiencies improved significantly by adjusting electrolytes' pHs.
• Lead as cathode material outputs superior performance.

CO2 can be converted to useful fuels by electrochemical processes. As an effective strategy to address greenhouse effect and energy storage shortage, electrochemical reduction of CO2 still needs major improvements on its efficiency and reactivity. Microfluidics provides the possibility to enhance the electrochemical performance, but few studies have focused on the virtual interface. This work demonstrates a dual electrolyte microfluidic reactor (DEMR) that improves the thermodynamic property and raises the electrochemical performance based on a laminar flow membrane-less architecture. Freed from hindrances of a membrane structure and thermodynamic limitations, DEMR could bring in 6 times higher reactivity and draws electrode potentials closer to the equilibrium status (corresponded to less electrode overpotentials). The cathode potential was reduced from −2.1 V to −0.82 V and the anode potential dropped from 1.7 V to 1 V. During the conversion of CO2, the peak Faradaic and energetic efficiencies were recorded as high as 95.6% at 143 mA/cm2 and 48.5% at 62 mA/cm2, respectively, and hence, facilitating future potential for larger-scale applications.