Scalable Conversion of Carbon Dioxide into Graphene for Electrochemical Energy Storage

Abstract

Graphene materials are regarded as one promising candidate for next-generation electrochemical energy storage devices due to its unique properties, such as high specific surface area and electrical conductivity. However, most of the up-to-date methodologies for producing graphene, such as chemical vapor deposition, mechanical exfoliation and reduction of graphite oxide, involve several severe drawbacks including heavy ion pollution, low yield and labor-intensive processes, which raise the cost and limit the scalability of graphene production. Therefore, a facile and cost-saving pathway for high-quality graphene synthesis is urgently needed. Combustion of fossil oil still represents a major energy source for electricity generation around the world, which releases a tremendous amount of CO2 to cause detrimental global warming. As a result, a prospective method for graphene production is to use the available CO2 as feedstock gas. But due to the inherent chemical stability of C=O bond, it is a great challenge to reduce CO2 into carbon materials by conventional techniques. It is well-established that magnesiothermic reaction is capable of dissociating strong chemical bonds, which offers a potential way for effective utilization of CO2. Herein, we present an ultra-fast magnesiothermic reaction to fabricate few-layer graphene with highly developed mesoporosity from CO2 and magnesium/magnesium oxide mixture. It is demonstrated that magnesium oxide acts as the crucial template to guide graphene formation and provide mesopores after acid rising. The ordered mesoporous graphene exhibits a high specific surface area of 709 m2 g-1 and a narrow pore size distribution around 4 nm. We further confirm its excellent electrochemical performance as supercapacitor electrodes. In IL electrolyte, the specific capacitance of MSG is as high as 260 F g-1 at 2 A g-1, corresponding to an energy density of 135.6 Wh kg-1, and can still maintain 173 F g-1 at an ultra-high rate of 100 A g-1. This excellent rate capability performance gives birth to an unprecedented power density of 7684 kW kg-1. Moreover, the electrochemical stability is demonstrated by a high capacitance retention of 90% after 1 million cycles of rapid charge/discharge at 100 A g-1. We believe our present work will give a new insight into the production of high-quality graphene materials. Fig. 1 Ordered mesoporous graphene prepared by ultra-fast magnesiothermic reaction Figure 1