Capture and Electrochemical Reduction of CO₂ Using Molten Alkali Metal Borates

Abstract

Molten alkali metal borates are a class of molten salts that have recently shown promise as high-temperature sorbents for capture of CO 2 and other acid gases. Thermal swing systems based on molten borates have demonstrated CO 2 capture capacities greater than those of amines, enabling efficient recovery of high-temperature heat in flue gas without practical concerns commonly associated with solid sorbents at these temperatures. In this work, we exploited generation of carbonates upon CO 2 capture by borates to enable their use as electrolytic media for carbon nanotube (CNT) synthesis by CO 2 splitting. Here, we report the conditions necessary to synthesize valuable multiwalled CNTs by CO 2 capture and conversion as a sustainable alternative to conventional carbon-intensive CNT synthesis techniques. Effects of cathode materials and operating conditions are quantified in sodium lithium borate, achieving significantly higher CO 2 uptake capacities than alkali metal carbonate salts for conversion of CO 2 into CNTs in the 550−650 °C range.

Salt-assisted synthesis of advanced carbon-based materials for energy-related applications

“…In their process, molten alkali metal borates were used as electrolyte which can capture CO 2 generating carbonate. 97 Wang et al presented an electrosynthesis to convert CO 2 into unusual nano- and micro-dimensioned morphology carbon in molten carbonate. The resulting carbon exhibited a wide range of potential uses, including batteries, supercapacitors, compression devices, electromagnetic wave shielding and sensors.…”