3D Graphene Materials from the Reduction of CO2

Document Type

Article

Publication Date

12-24-2020

Department

Department of Materials Science and Engineering

Abstract

Conspectus

The content of carbon dioxide (CO2) in the atmosphere has been continuously growing and threatens the global environment by contributing to the greenhouse effect. The conversion of CO2 directly into value-added chemicals could not only reduce CO2 emission but also make valuable use of the waste gas. However, achieving a highly efficient CO2 conversion with high product selectivity and low energy cost remains a great challenge.

Graphene, one of the most important engineering materials with a wide range of applications, is generally synthesized with valuable hydrocarbons as carbon sources. Producing versatile graphene materials directly from CO2 is intriguing and of profound meaning. Furthermore, it is of critical importance to produce 3D-structured graphene materials, which can avoid the restacking of the graphene sheets and thus keep the graphene properties for practical applications.

Alkali-metal-based exothermic reactions with inorganic carbon compounds, which have been discovered by our group since 2013, offer ideal solutions for efficient CO2 utilization and cost-effective 3D graphene production. In the reactions, alkali metal salts formed simultaneously with the graphenization of CO2 and served as in situ templates for creating the splendid microscale 3D structured graphene materials, which could hardly be achieved using other methods. Meanwhile, the etching effect of CO2 molecules can realize controlled engineering of unique surface porous structures of the formed 3D graphene. Accordingly, diverse 3D graphene materials featuring fascinating properties that are desired for energy-related and environmental applications can be facilely obtained by tuning the conditions for the reactions of CO2 with alkali metals.

This Account provides an overview of the 3D graphene materials from the reduction of CO2 via the state-of-the-art alkali-metal-chemistry-based strategy. After an emphasis on the significance of the CO2-to-graphene conversion process, the alkali-metal-based chemistry for CO2 conversion is introduced by delineating the thermodynamics of the reactions between CO2 and alkali metals and the forming mechanism of the 3D-structured graphene materials as well as the carbon etching effect of CO2. Subsequently, as typical examples, 3D cauliflower-fungus-like graphene, 3D crape myrtle flower-like graphene and mesochannel carbon nanowalls, 3D honeycomb-like structured graphene, and 3D surface-microporous graphene are specifically discussed in terms of their synthesis processes, structural characteristics, and reaction-condition-dependent properties. Furthermore, the great promise of these CO2-derived graphene materials for application in solar cells, supercapacitors, batteries, and environmental remediation are demonstrated. Finally, the challenges remaining in this area and the directions for its future development are addressed.

Publication Title

Accounts of Materials Research

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