Sustainable Synthesis of Cr₇C₃, Cr₂AlC, and Their Derived Porous Carbons in Molten Salts

Abstract

Carbide-derived materials including porous carbon and MXenes have received tremendous interest in recent years. Herein, we report a sustainable route direct from low-cost metal oxides/carbon (MOs/C) powders to metal carbides (MCs) and then to porous carbidederived carbons (CDCs). With the assistance of a solid oxide membrane (SOM), Cr 7 C 3 and Cr 2 AlC have been first synthesized from Cr 2 O 3 /C and Cr 2 O 3 /Al 2 O 3 /C powder mixtures, respectively. The synthesis pathway typically comprises electrochemical compounding, electrochemical reduction, and in situ carbonization processes. The Cr 7 C 3 and Cr 2 AlC with similar homogeneous nodular structure have been further in situ electrochemically converted into porous CDC materials. The as-prepared CDCs with amorphous and graphitic structures are hierarchical meso-/ macroporous carbon materials. Besides, the CDCs as an anode for lithium ion batteries were evaluated for their electrochemical performance. The results show that the discharge capacity of Cr 2 AlC-CDC can stay at 248 mAh g −1 after 100 cycles at 100 mA g −1 , demonstrating stable cyclic performance. The molten-salt electrochemical reduction−etching process provides a new method for synthesizing various CDC materials.

Molten Salt Electrosynthesis of Cr2AlC-Derived Porous Carbon for Supercapacitors

“…GCD profiles of the CDC samples obtained at different temperatures and their cycling performances at 100 mA g –1 are shown in Figure S4. The discharge capacity of the first and second cycles for the CDC obtained under 900 °C are 571 and 265 mAh g –1 , respectively, which are similar to the CDC obtained from Cr 2 O 3 /Al 2 O 3 /C in our recent work . However, the CDC obtained under 600 °C in this work possesses larger discharge capacity, which demonstrates 851 and 330 mAh g –1 at first and second cycles, respectively.…”

“…Furthermore, the performance of the synthesized CDC as anode material for the Li-ion battery was also investigated and compared with our previous work . GCD profiles of the CDC samples obtained at different temperatures and their cycling performances at 100 mA g –1 are shown in Figure S4.…”

“…32−35 In fact, the electrochemical synthetic method has been utilized to synthesize micro/nanostructured metal carbides in molten salt, 36−39 which provides a facile electrochemical route to synthesize CDC through combination with the electrochemical in situ etching process. 14 In our previous work, 40 Cr 2 AlC (a typical M 2 AX phase material) and its derived carbon have been successfully synthesized through the facile route (Cr 2 O 3 /Al 2 O 3 /C → Cr 2 AlC → CDC), and the performance of the prepared CDC for Li-ion batteries demonstrated excellent cyclic stability. However, the molten salt electrochemical etching mechanism and the modification of the pore structure as well as the capacitive performance of the MAX phase-derived CDC for supercapacitors are still ambiguous.…”

In-situ synthesis of zirconium oxycarbide by electroreduction of ZrO2/C in molten salt

“…In recent years, researchers have studied and proposed a series of molten salt electrolysis processes to prepare carbide materials [17][18][19][20]. Molten salt electrolysis provides a convenient and fairly easy way to obtain carbide materials.…”

Hybrid synthesis of zirconium oxycarbide nanopowders with defined and controlled composition

“…Other methods like spark plasma sintering or solid-state synthesis with carbide precursors are known but are equally demanding in terms of synthesis conditions. Electrochemical and mechanochemical methods also offer a convenient and rather easy access to carbide materials 13–16. As a completely different method, the gelation procedure is long in use as a rather easy approach to synthesize a plethora of different ceramics, including also carbides 17.…”