The Effect of Solvothermal Conditions on the Properties of Three-Dimensional N-Doped Graphene Aerogels

Abstract

Low-density three-dimensional (3D) N-doped graphene aerogels by a one-step solvothermal method in the presence of ethylenediamine (EDA) are reported. The gelation, formation, and properties of the aerogels were studied with solvothermal conditions, namely, operating temperature, time, graphene oxide (GO) concentration, and the GO/EDA w/w ratio. Two ranges of solvothermal conditions are employed: one involving an operating temperature below 100 °C and a conventional chemical reduction of GO with EDA at atmospheric pressure and a second one employing a higher temperature range up to 165 and a high pressure reduction with EDA. The results show that both solvothermal approaches allow for the fabrication of homogeneous N-doped 3D graphene aerogels with density values close to 10 mg cm−3. The measurements indicated that low values of GO concentration, temperature, and EDA are optimum for obtaining low-density 3D aerogels. N doping is improved with an EDA amount in lower temperature conditions. The N doping mechanism below 100 °C is dominated by the epoxy ring opening while at temperatures up to 165 °C both epoxy ring opening and amidation take place. The CO2 adsorption properties are strongly controlled by the nitrogen configuration, namely, pyridinic nitrogen in terms of its density.

Effect of Varying Amine Functionalities on CO2 Capture of Carboxylated Graphene Oxide-Based Cryogels

“…In this respect, one of the most used and preferred methods is the hydrothermal one, due to its low cost and easy implementation. By applying the simultaneous reduction and self-assembly of GO in the presence of amines and a subsequent freeze-drying procedure, aerogels could be synthesized to tackle the urgent environmental matter of highly selective and efficient CO 2 capture [8][9][10][11][12][13][14].…”

“…Concerning GO, approaches such as narrowing of GO size distribution [19] by employing different mesh size of the parent graphite for oxidation or the control of the oxidation degree were studied [20]. Our group has previously reported on the effect of simple hydrothermal synthesis conditions on the gelation and formation, as well as the effect of GO synthesis conditions on the CO 2 capture properties of ethylenediamine (EDA)-impregnated GO-based 3D monoliths [8,9]. Other studies considered the impregnation with amines such as EDA for obtaining 3D monoliths with improved conductivity and mechanical properties [21].…”

“…The nitrogen content was reported to be greatly influenced by the choice of solvent [16,17], which is usually an organic one. Various reports indicated the N configuration has marked effect on CO 2 conversion and uptake, selectivity and activity of doped material [8,9,[22][23][24][25][26][27]. The type of N configuration could be tailored by suitable synthesis conditions.…”

Synthesis and Electrochemical Study of Three-Dimensional Graphene-Based Nanomaterials for Energy Applications

“…N-doping on 3D graphene has been explored through various routes, namely hydrothermal, solvothermal, thermal treatment, etc. [ 31 , 57 , 58 ]. The deposition of small quantities of metal nanoparticles such as Pd on graphene can enhance its ORR activities [ 59 , 60 ].…”

Further Thermal Reduction of Reduced Graphene Oxide Aerogel with Excellent Rate Performance for Supercapacitors

“…In consideration of this situation, one effective method was to prepare various composites based on 3DG via loading active electrode materials onto the 3DG framework, including transition metal compounds [15][16][17][18][19] and conducting polymers [20,21], etc. [22][23][24][25], for further improving the performance. The specific capacitance has been enhanced up to several thousand F·g −1 [26].…”