A New, Efficient Conversion Technology to Transform Ambient CO₂ to Valuable, Carbon-Based Fuel via Molten Salt Electrochemistry

Abstract

Climate warming and environmental problems caused by the excessive consumption of fossil energy and massive CO2 emissions have seriously damaged the human living environment. This paper develops a new green, efficient, and environmentally friendly CO2 capture and conversion method, which is a crucial way to alleviate the greenhouse effect. In this study, alkali metal carbonates (and the corresponding hydroxides) are fused and blended to construct a liquid molten salt electrolyte system with excellent performance, which is applied to synthesize carbon materials or carbon-based fuel gas. By regulating the electrolyte composition and electrolysis parameters, carbon-based fuels with different micro-morphologies and compositions can be prepared in a controllable manner. In pure Li2CO3 electrolyte, carbon nanotubes (CNTs) with a high value are synthesized at 750 °C with, initially, 10 mA/cm2 and, finally, with 100 mA/cm2. Carbon spheres are obtained in Li-Ca-Ba at 750 °C with 200 mA/cm2, while honeycomb carbon is generated in the electrolyte of Li-Na-K at 450 °C with 450 mA/cm2. Syngas (33.6%) or CH4-rich fuel gas (40.1%) can also be obtained by adding LiOH into the electrolyte under 500 °C at 2.0 V and 3.2 V, respectively. This paper provides a new way of utilizing CO2 resources and a new sustainable green development.

Keywords

• electrolyte of carbonate and hydroxide
• electrochemical reduction of CO₂
• co-electrolysis of CO₂ and H₂O
• carbon-based materials
• syngas and CH₄-rich fuel gas