CO2 Conversion into N-Doped Carbon Nanomesh Sheets | ACS

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CO Conversion into N-doped Carbon Nanomesh Sheets Chunxiao Xu, Pengwan Chen, Kaiyuan Liu, Xin Gao, and Liyong Du ACS Appl. Nano Mater., Just Accepted Manuscript • DOI: 10.1021/acsanm.9b00377 • Publication Date (Web): 07 May 2019 Downloaded from http://pubs.acs.org on May 8, 2019

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ACS Applied Nano Materials

CO2 Conversion into N-doped Carbon Nanomesh Sheets Chunxiao Xu,a Pengwan Chen,*b Kaiyuan Liu,b Xin Gao,b,c and Liyong Dub a

Aerospace Institute of Advanced Materials & Processing Technology, No. 40 Yard

Yungang north residential community, Fengtai District, Beijing 100074, P. R. China b

State Key Laboratory of Explosion Science and Technology, Beijing Institute of

Technology, No. 5 Zhongguancun South Street, Haidian District, Beijing 100081, P. R. China c

Institute of Pulse Power Science, Kumamoto University, 2-39-1 Kurokami, Chuo-ku,

Kumamoto 860-8555, Japan. *Corresponding author. E-mail: [email protected] (Pengwan Chen)

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ABSTRACT. A new type of ultrathin N-doped carbon nanomesh (NCM) sheet derived from CO2 is prepared via a self-sustained sol-pyrolysis approach, which offers great promise for conversion of emitted CO2 to value-added chemicals in large scale. The newly prepared NCM products, having well-formed two- to four-atom-thick sheet structure, good nitrogen doping level (2.88 at%), high specific surface area (888 m2 g−1) and large hierarchical pores volume (2.05 cm3 g−1), possess superior half-wave potential (0.81 V vs RHE), kinetic limiting current (4.0 mA cm−2), tolerance to methanol crossover effect and stability against O2 reduction reaction in alkaline medium in fuel cells. More importantly, this general sol-pyrolysis approach greatly enhances reaction controllability and product selectivity for the thermochemical reduction of CO2, thus increasing the application potential of this methodology in both research laboratories and industries. KEYWORDS. CO2 conversion, carbon nanomesh, nitrogen doping, sol-pyrolysis, oxygen reduction reaction

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Introduction The carbon dioxide (CO2) emission is a matter of public concern related to global warming and climate change, thus, novel technologies for CO2 reduction are urgently needed such as capture, immobilization and sequestration, and also conversion CO2 into commodity chemicals [1–3]. One vision for such a technology is using CO2 as a raw material for the preparation of carbonaceous products via thermochemical reduction. This could lessen the amount of CO2 released into the atmosphere, and provide many value-added carbonaceous materials such as diamond [4], carbon nanotube [5], porous carbon [6], graphene [7–11], graphene oxide [12] and N-doped graphene [13]. However, apart from the energy- and time-consuming of most of these reduction approaches, the traditional thermochemical reaction which directly use gaseous CO2 as a carbon source suffers from the difficulty of controlling the conversion process and of selecting the product needed, which limits its practical application. Recent researches show that the reaction along a solution or sol-gel medium offers some particular advantages, such as atomic level mixing of precursors and greater control over particle morphology and size [14]. Here, we demonstrate a scalable and self-sustained sol-pyrolysis process for the conversion of CO2, which adsorbed in ethanol amine solution, directly to N-doped carbon nanomesh (NCM) sheets in high yield using magnesium powders as complexing and template agent. The reaction between CO2 and magnesium for the production of carbonaceous nanomaterial has been widely studied. Typically, Mg burns in CO2 environment to 3



produce MgO and carbon powder [15], this approach was later utilized to produce fewlayer graphene nanosheets [7,8]. In our earlier study, gaseous CO2 was adsorbed in noncarbon hydrazine monohydrate, and then reacted with Mg to generate N-doped carbon foam through a combustion pyrolysis process, which develops a more controllable and cost-effective methodology of constructing carbonaceous materials from CO2, and also confirms that carbon can be produced direct from CO2 within this methodology. In this work, we introduce ethanol amine solution into the initial reaction of CO2 and Mg, and synthesis NCM sheets through controlling the adding amount of Mg. Compared with hydrazine monohydrate, the usage of ethanol amine offers potential advantages for conversion of CO2, such as low toxicity and corrosiveness. In addition, the decomposition of ethanol amine is relatively mild and generate less gas, which is helpful for constructing large-size and uniform products. More importantly, ethanol amine solution has been used in industry for chemical sorption of CO2. In the present, the industrial adsorption method with ethanol amine solution also encounters difficulty of consuming large amounts of energy during the solvent regeneration process [16,17]. Therefore, using this industrial solution to both absorb CO2 and use it as a carbon source for NCM sheets synthesis would be like achieving two things at one stroke in the aspect of saving supplying energy and protecting our environment. Heteroatom-doped carbon nanomesh materials, which own high density in-plane nanoholes, high specific surface area and large number of defective edges, have attracted a great attention in the electrochemical field due to their enhanced surface 4


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properties, rapid diffusion of electrolytes, as well as fast transportation of charge carriers [18-21]. These outstanding features may also enable NCM sheets to be promising components in high-performance electrochemical devices such as fuel cells, lithium-ion batteries, and supercapacitors. Herein, due to the homogeneous mixing of the reactants, the high temperature and the short duration of the reaction, moreover the great generation of gases through the sol-pyrolysis process, the NCM sheets obtained show interesting properties including in situ nitrogen doping with level of 2.88 at%, well-formed two- to four-atom-thick layer arrangement, large specific surface area of 888 m2 g−1 and high pores volume of 2.05 cm3 g−1. Taking account of the synergistic effects of the characteristics, NCM electrodes for oxygen reduction reaction (ORR) in fuel cells are prepared and tested in order to determine the electrochemical performance of the synthesized NCM sheets. Results and discussion Fig. 1 illustrates the overall fabrication method of NCM sheets using CO2 gas and ethanol amine solution as reactants that undergo chemisorption, solation and selfsustained combustion pyrolysis process. In a typical experiment, the emitted gaseous CO2 is adsorbed into ethanol amine at room temperature that forming a carbaminate solution (Equation 1)[22]. The addition of an excessive quantity of magnesium powder and its dissolution into the above solution leads to the obtain of a homogeneous sol medium through a irreversible redox reaction between NH3+ and Mg spontaneously, and a consecutive complexation process between formate ions and Mg2+ in the solution 5



(Fig.S1, Equation 2). Herein, the ethanol amine solution serves as both CO2 adsorbent and Mg2+ complexing agent, which contributes to the solation process that can raise the likelihood of chemical modification with the utilization of CO2. Subsequently, the combustion pyrolysis process is initiated using an electrically heated tungsten filament, and then self-sustained for a short period of time. The combustion pyrolysis process is shown in Equation 3. Finally, the NCM sheets are achieved after etching away MgO composition, then washing with deionized water repeatedly, followed by freeze dried. This sol-pyrolysis process employs cheap and raw materials, and the liquid phase reaction is easy to achieve a gradual scale up, thus allow the large-scale production of carbon materials with improved controllability for reaction process and selectivity for the products. Throughout this approach, Mg powder is used to provide metal-ammonia complex ion and energy for self-sustained combustion. The combustion temperature, carbon conversion rate and physicochemical structure of the products are investigated through controlling the adding amount of Mg, which is determined by a relative ratio ϕ, and the prepared samples are denoted as NCM-1,-3,-5,-7,-9 correspondingly in this work. CO2 + 2HOC2H4NH2↔HOC2H4NHCOO ― + HOC2H4NH3+ (1) 2HOC2H4NHCOO ― + 2HOC2H4NH3+ + Mg→(HOC2H4NHCOO)2Mg + 2HOC2H4NH 2 + H2 (2)

(HOC2H4NHCOO)2Mg + 2HOC2H4NH2 + ϕMg + (ϕ/2 +3)O2→ 10C + (ϕ + 1)MgO + 2N2 + 13H2O (3)

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Fig. 1. Overall fabrication of NCM sheets from gas state CO2 via chemisorption, solation, self-sustained pyrolysis and acid etching process. XRD results give the structure of the as-obtained NCM sheets (Fig. 2a). Strong diffraction peaks indexed at ca. 26° and 44° correspond to the (002) and (101) crystal planes of graphite. Meanwhile, the spectrum shows no sign of other characteristic diffraction peak, indicating that MgO impurities have been cleared successfully through acid etching (Fig. S2). A progressive right shifting of (002) peak of NCM sheets can be seen with raising the ratio of Mg (ϕ) from 1 to 9, which is assigned to the intensive graphitization of NCM sheets. Raman spectra shows that the NCM sheets exhibit four bands located at around 1327, 1589, 2636 and 2898 cm−1, which correspond to the D band due to sp3 defects, G band due to the pristine sp2 lattice, 2D band and D+G band (Fig. 2b), respectively, indicating a limited stacking order with a large amount of edges and cross-link structures [23]. The vibration of disorder and defects in the graphitic layers result in the formation of D band [13]. Thus, the strong D band and high ID/IG 7



ratio (1.68 for NCM-1, 1.72 for NCM-3, 1.60 for NCM-5, 1.58 for NCM-7, 1.74 for NCM-9) observed in the NCM sheets imply the existence of a large amount of topological defects due to pyrolysis synthesis process and N-doping in the hexagonal basal planes. The 2D band without a graphite shoulder blue shifts to ca. 2636 cm−1, meanwhile, the broad 2D band with low I2D/IG ratio (0.09 for NCM-1, 0.10 for NCM3, 0.10 for NCM-5, 0.12 for NCM-7, 0.11 for NCM-9) reveals that NCM sheets consist of the few-layers [7,24]. In general, the degree of disorder is barely influenced when changing the Mg content, and the NCM sheets possess similar level of layer thickness, edges and wrinkles.

Fig. 2. (a) XRD pattern and (b) Raman spectra of the NCM sheets with different amount of Mg powders (ϕ = 1, 3, 5, 7, 9). Theoretical calculated adiabatic temperature (Tad) and measured maximum temperature are further employed to understand the causes of NCM sheets. For this self-sustained combustion pyrolysis, Tad can be readily estimated as a traditional self-propagating high-temperature synthesis (SHS) process using Equation S1 [7,25,26] and “Thermo” software [26], respectively. As shown in Fig. 3, Tad of NCM-1,3,5,7,9 is more than 8


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1800K, confirming the self-sustainable synthesis process [27]. With raising the ratio of Mg (ϕ) from 0 to 4, Tad increases accordingly, and the results obtained through Equation S1 are in good agreement with those of “Thermo” software. However, when increasing ϕ from 5 to 10 (Tad approaches 3000K), Tad results obtained through Equation S1 continue to increase while those of “Thermo” software gradually level off. In theory, the thermodynamic calculation through “Thermo” software gives more realistic results, because it considers the latent heats of phase transformations when balancing the enthalpy (Table S1). The maximum temperature measured during this experiment has the same tendency with the calculated Tad through “Thermo”, further confirming the correctness of theoretical calculations. The measured maximum temperature of NCM sheets, by contrast, is always lower than the calculated Tad (Fig. 3, S3). This inconsistency can be attributed to the thermocouple signal delay or/and to the nonadiabatic experimental conditions. The carbon conversion rate is further investigated in Fig. 3. It is noteworthy that the conversion rate also follows the trend of Tad variation, which go through a growing process to achieve balance with increase of Mg content. A stabilisation around 30% of conversion ratio is achieved when ϕ ≥ 5. Thus, the Tad and conversion ratio can be effectively regulated by changing the amount of Mg powders, thereby making the control of the combustion pyrolysis process possible. On the base of consideration of the XRD, Raman, Tad and conversion ratio results, the increase of Mg content can raise the carbon conversion rate on certain level, but show little effects on the carbon structure. Therefore, ϕ = 5 is selected as a typical sample in the following analysis. 9



Fig. 3. Tad, measured maximum temperature and experimental conversion ratio of NCM sheets with different amount of Mg powders (ϕ range from 0 to 10).

The morphology of the as-prepared NCM-5 sheet is confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterization, and the NCM sheets without entirely etching away MgO (Fig. 4a–d, S4, S5) are also investigated for comparison. Since MgO has been extensively investigated as a hard template for the preparation of carbon thin layers and porous structures owing to its structural and thermal stabilities [7,28], we estimate that the MgO formed during the pyrolysis process has an important effect on the product morphology. As can be seen from Fig. 4a, a dense collection of bright spots are displayed, which correspond to MgO particles on the NCM sheets. As expected, TEM images illustrate the presence of ≈ 10 nm MgO nanoparticles in the NCM sheets holes. Meanwhile, large-area MgO completely cover the carbon nanomesh before etching treatment (Fig. 4c). This investigation demonstrates the in-situ formation of MgO and its template role for both NCM sheets growth and nanoholes creation (Fig. S6). By contrast pure NCM sheets 10


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with a average size of about 10 μm can be discerned after etching as displayed in Fig. 4b and S7, moreover, wrinkled sheet walls with well-defined adjacent interlayer voids can be clearly observed. Fig. 4d shows the corresponding TEM and high resolution TEM (HRTEM) images. NCM sheets display abundant mesoporous structures with ≈ 9 nm pore size. Meanwhile, the pores edge displays around 4 graphite layers with a dspacing of 0.34 nm, which is in correspondence with (002) plane from the XRD results (Fig S8). Significantly, NCM sheets show unique non-bending sheet-like structure with uniform holes and with two- to four-layer carbonatomic thickness (ca. 1.5nm) as further confirmed by atomic force microscopy (AFM, Fig. 4e, S9). The specific surface area (SSA) measurement is conducted using Brunauer-EmmettTeller (BET) method according to nitrogen adsorption-desorption curves. The result reveals that NCM-5 has a mesopore hysteresis loop, which is attributed to type-IV isotherm according to IUPAC classification (Fig. S10). The SSA of NCM-5 is as high as 888 m2 g−1, twice of newly reported graphene foam (362 m2 g−1) [29]. Furthermore, NCM-5 sheets exhibit a broad pore size distribution (1 to 100 nm), and a large pore volume (2.05 cm3 g-1) the micropore, mesopore volume and macropore volumes are found to be equal to 0.13 cm3 g-1 (6%), 1.66 cm3 g-1 (81%) and 0.26 cm3 g-1 (13%) respectively (Fig. 4f, Table S2). The majority of mesopores have mainly a diameter in the range 3.2-9.0 nm, which is consistent with TEM results. The creation of such varied pore structure in the NCM sheets maybe attributed to water vapor and nitrogen gas generated and released through the thermal pyrolysis process, creating relatively large 11



pores (macropores and mesopores), whereas MgO molecules removed through acid etching left behind small pores (mesopores).

Fig. 4. SEM and TEM images of NCM-5 sheet (a, c) without entirely acid etching (areas marked in (c) are the in-situ synthesized MgO templates), (b, d) after chemical etching, insets of (d) is the corresponding high-magnification TEM image. (e) AFM image and the corresponding height profile along a line scan for an NCM-5 sheet. (f) Pore size distribution curve and corresponding cumulative pore volume. To probe N atoms in our NCM sheets, we carried out X-ray photoelectron spectroscopy 12


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(XPS) and Energy-dispersive X-ray spectroscopy (EDS) analysis. XPS spectra (Fig. 5a, S11) reveals a strong C 1s peak at 284 eV, a O 1s peak at ca. 532 eV related to the presence of 4.34 at% of oxygen, and a relatively weak N 1s peak at ca. 400 eV. The N atomic ratio of NCM-5 calculated from XPS equals 2.88 %, which is consistent with the EDS results (Fig. S12, Table S3,S4). The high-resolution N 1s spectrum given in Fig. 5b illustrates the formation of pyridine-N (398.2 eV), pyrrolic-N (399.7 eV), graphitic-N (401.0 eV) and oxidized N (402.0 eV) species within carbon backbones [30,31]. Therefore, the ethanol amine serves as a sole nitrogen source for the NCM sheets, and the nitrogen atoms have been integrated into the carbon hexagon rings, which is strongly desired for the electrochemical characteristics and can play an important role in ORR performance [32–37].

Fig. 5. (a) XPS spectrum and corresponding (b) high-resolution N 1s XPS spectra of NCM-5 sheet.

Metal-free heteroatom-doped carbon materials with nano-size pore structure are of great interest owing to their electrocatalytic activities towards the ORR in fuel cell [38– 13



44]. Thus, ORR performance of NCM-5 is extensively investigated and compared to the commercial 20 wt% Pt/C electrode under the same condition of experiment. The cyclic voltammogram (CV) measured in N2 or O2-saturated 0.1 M KOH solutions with Ag/AgCl as a reference electrode is displayed in Fig. 6a. There have no redox peaks for NCM-5 in case of oxygen absence condition. By contrast, remarkable cathodic features are observed in O2-saturated electrolytes at ca. 0.84 V versus reversible hydrogen electrode (RHE), which is close to Pt/C (0.89 V vs RHE). The linear sweep voltammograms (LSVs) test is conducted on the rotating ring-disk electrode (RRED) at 1600 rpm (Fig. 6b). The NCM-5 sample shows a half-wave potential of 0.81 V vs RHE, and a high diffusion-limited current density of 4.0 mA cm−2, demonstrating much the same ORR activity compared with Pt/C electrode (0.83 V vs RHE, 5.0 mA cm−2). Moreover, NCM-5 has a high onset potential of ca. 0.96 V, superior to that of many typical N-doped carbon materials and comparable porous carbon-based materials (Table S5), thus highlighting the remarkable electrocatalytic activity of our NCM sheets. This efficient electrocatalytic performance can be related to the obtained nanomesh porous structure in conjunction with their N-doping. Hierarchical nanomesh structure with high-density micro-, meso- and macropores can greatly improve the mass transport during electrochemical reaction process. Few-layer carbon sheets with sufficient reactive catalytic surface and sites can facilitate the thermodynamic and kinetic of electrochemical catalysis reaction. Meanwhile, the incorporation of nitrogen into carbon skeleton can regulate the charge distribution over the carbon framework and the doped nitrogen heteroatoms provide abundant active sites through an induced electronic 14


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interaction with their adjacent carbon atoms, as well as through the created defects in the carbon structure, constituting asset O2 adsorption sites [45–47].

Fig. 6. (a) CV curves of NCM-5 sheet and Pt/C in an O2-saturated 0.1 M KOH solution at a scan rate of 10 mV s–1. (b) LSV on a RRDE at 1600 rpm. (c) LSV curves of the NCM-5 sheets under varied rotating speeds. Inset in (c) displays the corresponding KL plots. (d) HO2- production and n of NCM-5 derived from the RRED analysis. (e) Chronoamperometric responses of NCM-5 and Pt/C. The arrow in (e) represents adding 15



8 mL methanol into 80 mL 0.1 m electrolyte of KOH. (f) Durability measurement of NCM-5 and Pt/C. The LSV curves with varied electrode rotation speeds are further studied in the O2saturated 0.1 M KOH electrolyte. As shown in Figure 6c, diffusion current densities increased proportionally with a progressive increase of the rotation speed. Meanwhile, The diffusion limiting current is achieved through expanding the potential range. The mean transferred electron number (n) per O2 molecule is determined from KouteckyLevich (K-L) plots (Fig. 6c, inset) using the K-L equation (Equation S2 and S3) is found to equal ≈ 3.5, indicating a nearly four-electron (4e) pathway of the NCM-5 for the ORR. In order to approve the calculated n and to determine the peroxide yield of NCM5 electrode in the ORR process, ring and disk currents over 0.17-0.77 V potential range from the RRDE curves are utilized (Equation S4 and S5). As shown in Fig. 6d, n is found to be ≈ 3.6, which is in good agreement with K-L results. Meanwhile, the peroxide yield is found to exceed 20 % over almost the entire potential range studied, confirming again the nearly 4e ORR process for the NCM electrode. The methanol tolerant ability and long-time durability are two significant factors as an ORR electrocatalyst of fuel cells. Hence, chronoamperometric measurements of both NCM-5 and Pt/C (20 wt%) catalysts at 0.6 V versus RHE are performed and compared in O2-saturated 0.1 M solution of KOH. As can be seen from Fig. 6e, the ORR current response of the NCM sheets shows no obvious change after adding methanol (10 vol%) into the electrolyte, while a significant loss of current density is observed for the Pt/C 16


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catalyst, demonstrating a much better immunity toward methanol crossover for the NCM electrode. The NCM sheets further demonstrate an outstanding durability after continuous testing for 12h (Fig. 6f). Almost no current reduction (ca. 2 %) is observed during the period, whereas Pt/C lost more than 14 % of its initial activity, confirming a superior stability of ORR on NCM sheets. These results prove that the NCM sheets obtained from sol-pyrolysis conversion of CO2 are very promising metal-free catalysts for efficient ORR in alkaline solutions. This efficient electrocatalytic performance can be related to the obtained porous structure of NCM sheets in conjunction with their Ndoping. Extremely thin carbon sheets with hierarchical porous structure can greatly improve the mass transport of electrochemical reactions [18,48,49]. Meanwhile, the doped nitrogen heteroatoms provide abundant active sites through an induced electronic interaction with their adjacent carbon atoms, as well as through the created defects in the carbon structure, constituting asset O2 adsorption sites [50,51]. Conclusions A general sol-pyrolysis process is developed to directly produce NCM sheets from captured CO2 in ethanol amine solution used in industrial routines. This process promotes the elimination of CO2 gas emissions while simultaneously ensures its beneficial use in large-scale production of valuable carbon materials. In such an approach, the ethanol amine is used as a CO2 adsorbent, a fuel, and a nitrogen source, whereas Mg powder participates in the reaction through playing the role of a complex metal ion, a template agent and an energy source for the self-sustained pyrolysis process. 17



The synthesized NCM sheets exhibit an excellent electrochemical performance in fuel cell thanks to their well-formed two- to four-atom-thick layer arrangement, in situ nitrogen doping, high surface area, and unique porous structure. In summary, our approach provides a new direction towards the large-scale production of carbon-based materials with outstanding properties derived from carbon dioxide. ASSOCIATED CONTENT Supporting Information The experimental section, Figure S1-Figure S12 and Table S1-Table S5. Experimental photographs of MEA, CO2-saturated MEA, and magnesium carbaminate sol. Measured combustion temperature-time profile of NCM sheets. XRD, EDS, XPS, high-resolution Mg 1s and N 1s XPS spectra results for NCM-5 catalysts and intermediate materials before pyrolysis and etching. SEM, TEM and the corresponding high-magnification HRTEM images of as-prepared NCM structure before acid etching and after etching treatment. Thermodynamic calculation of the adiabatic temperature and products using “Thermo” software package. ORR electrocatalytic performance of synthesized NCM5 sheets and other typical carbon-based materials in alkaline solution. AUTHOR INFORMATION Corresponding Author *E-mail: [email protected] 18


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ORCID https://orcid.org/0000-0002-4289-364X Notes The authors declare no competing financial interest. Acknowledgments The authors thank the financial support from the Project of State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology under Grant ZDKT18-01. The authors thank Ms. Zineb Benzait for editing the English. References [1] D.-A. Yang, H.-Y. Cho, J. Kim, S.-T. Yang, W.-S. Ahn, CO2 capture and conversion using Mg-MOF-74 prepared by a sonochemical method, Energy Environ. Sci. 5 (2012) 6465–6473. [2] N.S. Spinner, J.A. Vega, W.E. Mustain, Recent progress in the electrochemical conversion and utilization of CO2, Catal. Sci. Technol. 2 (2012) 19–28. [3] E.V. Kondratenko, G. Mul, J. Baltrusaitis, G.O. Larrazábal, Pérez-Ramírez, Status and perspectives of CO2 conversion into fuels and chemicals by catalytic, photocatalytic and electrocatalytic processes, Energy Environ. Sci. 6 (2013) 3112–3135. [4] Z. Lou, Q. Chen, Y. Zhang, W. Wang, Y. Qian, Diamond formation by reduction of carbon dioxide at low temperatures, J. Am. Chem. Soc. 125 (2003) 9302–9303. 19



[5] Z. Lou, C. Chen, Q. Chen, J. Gao, Formation of variously shaped carbon nanotubes in carbon dioxide–alkali metal (Li, Na) system, Carbon 43 (2005) 1084–1114. [6] C. Xu, S. Chen, L. Du, C. Li, X. Gao, J. Liu, L. Qu, P Chen, Scalable conversion of CO2 to N-doped carbon foam for efficient oxygen reduction reaction and lithium storage, ACS Sustainable Chem. Eng. 6 (2018) 3358–3366. [7] A. Chakrabarti, J. Lu, J.C. Skrabutenas, T. Xu, Z. Xiao, J.A. Maguireb, N.S. Hosmane, Conversion of carbon dioxide to few-layer graphene, J. Mater. Chem. 21 (2011) 9491–9493. [8] C. Li, X. Zhang, K. Wang, X. Sun, G. Liu, J. Li, H. Tian, J. Li, Y. Ma, Scalable self-propagating high-temperature synthesis of graphene for supercapacitors with superior power density and cyclic stability, Adv. Mater. 29 (2017) 1604690. [9] H.L. Poh, Z. Sofer, J. Luxa, M. Pumera, Transition metal-depleted graphenes for electrochemical applications via reduction of CO2 by Lithium, Small 10 (2014) 1529– 1535. [10] K. Smith, R. Parrish, W. Wei, Y. Liu, T. Li, Y.H. Hu, H. Xiong, Disordered 3D multi-layer graphene anode material from CO2 for sodium-ion batteries, ChemSusChem. 9 (2016) 1397–1402. [11] W. Wei, B. Hu, F. Jin, Z. Jing, Y. Li, A.A.G. Blanco, D.J. Stacchiola, Y.H. Hu, Potassium-chemical synthesis of 3D graphene from CO2 and its excellent performance 20


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CO2 Conversion into N-doped Carbon Nanomesh Sheets 259x153mm (300 x 300 DPI)


CO2 Conversion into N-Doped Carbon Nanomesh Sheets | ACS

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