Pure and Metal‐confining Carbon Nanotubes through Electrochemical Reduction of Carbon Dioxide in Ca‐based Molten Salts

Abstract

To be successfully implemented, an efficient conversion, affordable operation and high values of CO 2 -derived products by electrochemical conversion of CO 2 are yet to be addressed. Inspired by the natural CaO-CaCO 3 cycle, we herein introduce CaO into electrolysis of SnO 2 in affordable molten CaCl 2 -NaCl to establish an in situ capture and conversion of CO 2 . In situ capture of anodic CO 2 from graphite anode by the added CaO generates CaCO 3 . The consequent coelectrolysis of SnO 2 and CaCO 3 confines Sn in carbon nanotube (Sn@CNT) in cathode and increases current efficiency of O 2 evolution in graphite anode to 71.9 %. The intermediated CaC 2 is verified as the nuclei to direct a self-template generation of CNT, ensuring a CO 2 -CNT current efficiency and energy efficiency of 85.1 % and 44.8 %, respectively. The Sn@CNT integrates confined responses of Sn cores to external electrochemical or thermal stimuli with robust CNT sheaths, resulting in excellent Li storage performance and intriguing application as nanothermometer. The versatility of the molten salt electrolysis of CO 2 in Ca-based molten salts for template-free generation of advanced carbon materials is evidenced by the successful generation of pure CNT, Zn@CNT and Fe@CNT.

Structural design of FeCo alloy implanted into N,S co-doped carbon nanotubes via self-catalyzed growth for advanced liquid and flexible all-state-state Zn–air battery

“…37 The nucleation and growth mechanism of CNT induced by Fe 2 O 3 /Co@C was further validated by the successful generation of high-quality FeCo nanoparticles via the Fe/Co nucleus. 38 Fe/Co appeared to be doped into the grown walls of CNTs in the presence of N (Fig. 1g).…”

New Route of Acetylene Synthesis via Electrochemical Formation of Metal Carbides from CO2 in Chloride Melts

“…The potential decreased with time, eventually reaching a potential lower than 0 V at which metal electrodeposition proceeded. From the report that CaC 2 tends to form at potentials lower than Ca electrodeposition, 25 the reaction to form metal carbide was considered to have proceeded even at potentials lower than 0 V. The current efficiencies for C 2 H 2 gas generated by the reaction between the obtained samples and water (Figure 5b) were estimated to be 34% for NaCl−KCl− CaCl 2 −CaO system without CaC 2 and 68% for that with CaC 2 . The results indicated that the addition of CaC 2 into the melt enhanced the current efficiency because of the suppression of the dissolution of electrodeposited CaC 2 in the melt.…”

“…It has been reported that the carbon nanotube was formed through the mediation of CaC 2 in molten CaCO 3 −Na 2 CO 3 −K 2 CO 3 at 1073 K using a Ni-sheet cathode. 25 The acetylene gas can be produced by the reaction between the metallic carbides with water. In the conventional process, the CaC 2 is industrially manufactured by heating a mixture of quicklime and coke to about 2000 °C in an electric furnace.…”

“…On the other hand, the metallic carbides composed of alkali metals or alkali earth metals such as Li 2 C 2 and CaC 2 are attractive materials as a source of acetylene gas. It has been reported that the carbon nanotube was formed through the mediation of CaC 2 in molten CaCO 3 –Na 2 CO 3 –K 2 CO 3 at 1073 K using a Ni-sheet cathode . The acetylene gas can be produced by the reaction between the metallic carbides with water. normalC normala normalC 2 .25em or .25em normalL normali 2 C 2 + 2 H 2 normalO → C 2 H 2 + C a false( normalO normalH false) 2 .25em or .25em 2 L i O H In the conventional process, the CaC 2 is industrially manufactured by heating a mixture of quicklime and coke to about 2000 °C in an electric furnace. C a O + 3 normalC → normalC normala normalC 2 + C O Recently, the new production process of CaC 2 such as the coal-coke-electricity grading substitution method and utilizing low-rank coal-based oxygen-thermal and electro-thermal process toward achieving carbon neutrality have been proposed.…”

Molten Salt Electrolytic CO2-Derived Carbon-Based Nanomaterials for Energy Storage and Electrocatalysis: A Review

“…For instance, metals such as Ge, Sn, Zn, and Fe have been introduced to CO 2 -C to synthesize metal@CNTs or metal@carbon spheres through the coreduction of CO 2 and metal oxides (GeO 2 , SnO 2 , ZnO, and FeO) or utilization of a liquid zinc anode, thereby enhancing the LIBs' performance. 14,34,35 Regarding the applications of electrocatalysts, there have been few reports on employing metal-free CO 2 -C as electrocatalysts. To date, only approximately two studies have concentrated on its application in the two-electron (2e) oxygen reduction reaction (ORR).…”