Co-production of Few-layer Graphene and Hydrogen from Methane Pyrolysis Based on Cu and Metal Oxide-KCl Molten Medium

doi:10.15541/jim20240445

Abstract

Abstract:

Methane pyrolysis is a technology that utilizes fossil energy to produce high added value carbon materials and hydrogen. However, traditional methods, such as chemical vapor deposition (CVD) and molten metal catalysis, face challenges in the production of graphene, including catalyst deactivation, difficulty in separating graphene from the catalyst, and high reaction temperatures (≥1100 ℃), which limit their industrial applications. This study proposes an innovative approach to produce graphene by catalyzing methane pyrolysis using Cu and metal oxides-KCl molten medium. By adding metal oxides (Al₂O₃, TiO₂, ZrO₂, MgO, SiO₂) as dispersants, the dispersion of active Cu sites is enhanced. Notably, Cu/ZrO₂ with a Cu content of 50% (in volume) and Cu/MgO with a Cu content of 75% (in volume) catalysts enable the efficient production of few-layer graphene. Cu/ZrO₂ catalyst with a Cu content of 50% (in volume) exhibits the highest activity, achieving a methane conversion rate of 22%, a hydrogen production yield of 21.5 mmol/h, and formation of large-area and smooth few-layer graphene. This study provides a new technical route for co-production of graphene and hydrogen via methane pyrolysis, offering potential for large-scale graphene production in the future.

Key words: methane pyrolysis, molten medium, few-layer graphene, hydrogen, copper/metal oxide

CLC Number:

O643

YANG Mingkai, HUANG Zeai, ZHOU Yunxiao, LIU Tong, ZHANG Kuikui, TAN Hao, LIU Mengying, ZHAN Junjie, CHEN Guoxing, ZHOU Ying. Co-production of Few-layer Graphene and Hydrogen from Methane Pyrolysis Based on Cu and Metal Oxide-KCl Molten Medium[J]. Journal of Inorganic Materials, 2025, 40(5): 473-480.

Figures/Tables 16

Fig. 1 Effects of metal oxides and Cu contents on CH4 conversion rate (a) and hydrogen production yield (b)

Fig. 2 Effects of reaction time on CH4 conversion rate (a) and hydrogen production yield (b)

Fig. 3 Raman spectra of carbon materials produced using xCu/ZrO2 (a) and xCu/MgO (b) catalysts

Fig. 4 SEM images of carbon materials produced using xCu/ZrO2 catalysts (a) x=0; (b, c) x=25%; (d) x=50%; (e) x=75%; (f) x=100%

Fig. 5 SEM images of carbon materials produced using xCu/MgO catalysts (a) x=0; (b) x=25%; (c) x=50%; (d, e) x=75%; (f) x=100%

Fig. 6 (a-c) TEM images of carbon materials produced using 50%Cu/ZrO2 catalysts; (d) HRTEM image of carbon materials produced using 75%Cu/MgO catalysts

Fig. 7 XRD patterns of carbon materials produced using 50%Cu/MO catalysts

Fig. 8 TG curves of carbon materials produced using 50%Cu/MO catalysts

Fig. 9 Nitrogen adsorption-desorption isotherms (a) and pore size distributions (b) of carbon materials produced using 50%Cu/MO catalysts

Fig. 10 Schematic diagram of the reaction mechanism 1. Methane pyrolysis to few-layer graphene growth; 2. Few-layer graphene growth to separation; 3. Few-layer graphene separation to floating

Table 1 S1 Contents of carbon materials and impurity produced using 50%Cu/MO catalysts

Sample	Carbon/% (in mass)	Impurity/% (in mass)
50%Cu/SiO₂	43.4	56.6
50%Cu/MgO	67.5	32.5
50%Cu/ZrO₂	52.2	47.8
50%Cu/TiO₂	62.2	37.8
50%Cu/Al₂O₃	80.2	19.8

Table 2 S2 BET data for carbon materials produced using 50%Cu/MO catalysts

Sample	Specific surface area/(m²·g^-1)	Pore volume/ (cm³·g^-1)	Average pore diameter/nm
50%Cu/SiO₂	9.03	0.04	19.75
50%Cu/MgO	11.76	0.06	19.26
50%Cu/ZrO₂	10.33	0.05	19.76
50%Cu/TiO₂	13.45	0.07	21.86
50%Cu/Al₂O₃	12.52	0.07	20.78

Fig. 11 S1 Raman spectra of carbon materials produced using xCu/Al2O3 (a), xCu/TiO2 (b) and xCu/SiO2 (c) catalysts

Fig. 12 S2 SEM images of carbon materials produced using xCu/Al2O3 catalysts (a) x=0; (b) x=25%; (c, d) x=50%; (e) x=75%; (f) x=100%

Fig. 13 S3 SEM images of carbon materials produced using xCu/TiO2 catalysts (a) x=0; (b) x=25%; (c) x=50%; (d, e) x=75%; (f) x=100%

Fig. 14 S4 SEM images of carbon materials produced using xCu/SiO2 catalysts (a) x=0; (b) x=25%; (c) x=50%; (d) x=75%; (e, f) x=100%

References 32

[1]	马新华, 张国生, 唐红君, 等. 天然气在构建清洁低碳能源体系中的地位与作用. 石油科技论坛, 2022, 41(1): 18.
[2]	何展军, 黄敏, 林铁军, 等. 光热催化甲烷干重整研究进展. 物理化学学报, 2023, 39(9): 28.
[3]	PINAEVA L, NOSKOV A. Modern level of catalysts and technologies for the conversion of natural gas into syngas. Catalysis in Industry, 2022, 14(1): 66.
[4]	LI H, PEI W, YANG X, et al. Pt overlayer for direct oxidation of CH₄ to CH₃OH. Chinese Chemical Letters, 2023, 34(11): 108292.
[5]	SUN C, ZHAO K, YI Z. Research progress in catalytic total oxidation of methane. Journal of Inorganic Materials, 2023, 38(11): 1245.
[6]	SHEN X, WU D, FU X Z, et al. Highly selective conversion of methane to ethanol over CuFe₂O₄-carbon nanotube catalysts at low temperature. Chinese Chemical Letters, 2022, 33(1): 390.
[7]	CAO Y, YU W, HAN C, et al. Methane photooxidation with nearly 100% selectivity towards oxygenates: proton rebound ensures the regeneration of methanol. Angewandte Chemie International Edition, 2023, 135(18):e202302196.
[8]	黄泽皑, 周芸霄, 张魁魁, 等. 甲烷裂解制氢和碳材料工艺研究进展. 低碳化学与化工, 2024, 49(9): 1.
[9]	ABÁNADES A, RATHNAM R K, GEISSLER T, et al. Development of methane decarbonisation based on liquid metal technology for CO₂-free production of hydrogen. International Journal of Hydrogen Energy, 2016, 41(19): 8159.
[10]	LIU M, HUANG Z, ZHOU Y, et al. Optimized process for melt pyrolysis of methane to produce hydrogen and carbon black over Ni foam/NaCl-KCl catalyst. Processes, 2023, 11(2): 360.
[11]	ZHANG K, HUANG Z, YANG M, et al. Recent progress in melt pyrolysis: fabrication and applications of high-value carbon materials from abundant sources. SusMat, 2023, 3(5): 558.
[12]	ZHOU Y, HUANG Z, ZHANG K, et al. Economic analysis of hydrogen production and refueling station via molten-medium- catalyzed pyrolysis of natural gas process. International Journal of Hydrogen Energy, 2024, 62: 1205.
[13]	WALIMBE P, CHAUDHARI M. State-of-the-art advancements in studies and applications of graphene: a comprehensive review. Materials Today Sustainability, 2019, 6: 100026.
[14]	QAMAR S, RAMZAN N, ALEEM W. Graphene dispersion, functionalization techniques and applications: a review. Synthetic Metals, 2024, 307: 117697.
[15]	WANG L, LIRA P, HU G, et al. Graphene-based electrodes and catalysts for electroreduction of CO₂ to low-carbon alcohols. Materials Reports: Energy, 2023, 3(2): 100192.
[16]	WONG S I, LIN H, MA T, et al. Binary ionic liquid electrolyte design for ultrahigh-energy density graphene-based supercapacitors. Materials Reports: Energy, 2022, 2(2): 100093.
[17]	WU J, YU L, LIU S, et al. NiN₄/Cr Embedded graphene for electrochemical nitrogen fixation. Journal of Inorganic Materials, 2022, 37(10): 1141.
[18]	程熠, 王坤, 亓月, 等. 石墨烯纤维材料的化学气相沉积生长方法. 物理化学学报, 2022, 38(2): 40.
[19]	LI X, CAI W, AN J, et al. Large-area synthesis of high-quality and uniform graphene films on copper foils. Science, 2009, 324(5932): 1312.
[20]	CHAE S J, GÜNEŞ F, KIM K K, et al. Synthesis of large-area graphene layers on poly-nickel substrate by chemical vapor deposition: wrinkle formation. Advanced Materials, 2009, 21(22): 2328.
[21]	LUO D, WANG M, LI Y, et al. Adlayer-free large-area single crystal graphene grown on a Cu(111) foil. Advanced Materials, 2019, 31(35): 1903615.
[22]	AMONTREE J, YAN X, DIMARCO C S, et al. Reproducible graphene synthesis by oxygen-free chemical vapour deposition. Nature, 2024, 630(8017): 636.
[23]	UPHAM D C, AGARWAL V, KHECHFE A, et al. Catalytic molten metals for the direct conversion of methane to hydrogen and separable carbon. Science, 2017, 358(6365): 917.
[24]	TANG Y, PENG P, WANG S, et al. Continuous production of graphite nanosheets by bubbling chemical vapor deposition using molten copper. Chemistry of Materials, 2017, 29(19): 8404.
[25]	敖东羿. 多层高品质石墨烯的大量制备及其应用研究. 成都: 电子科技大学博士学位论文, 2020.
[26]	QIAO C, CHE J, WANG J, et al. Cost effective production of high quality multilayer graphene in molten Sn bubble column by using CH₄ as carbon source. Journal of Alloys and Compounds, 2023, 930: 167495.
[27]	PARKINSON B, PATZSCHKE C F, NIKOLIS D, et al. Methane pyrolysis in monovalent alkali halide salts: kinetics and pyrolytic carbon properties. International Journal of Hydrogen Energy, 2021, 46(9): 6225.
[28]	WANG H Y, LUA A C. Hydrogen production by thermocatalytic methane decomposition. Heat Transfer Engineering, 2013, 34(11/12): 896.
[29]	JONES R R, HOOPER D C, ZHANG L, et al. Raman techniques: fundamentals and frontiers. Nanoscale Research Letters, 2019, 14: 231.
[30]	LUONG D X, BETS K V, ALGOZEEB W A, et al. Gram-scale bottom-up flash graphene synthesis. Nature, 2020, 577(7792): 647.
[31]	LOSIC D, FARIVAR F, YAP P L, et al. Accounting carbonaceous counterfeits in graphene materials using the thermogravimetric analysis (TGA) approach. Analytical Chemistry, 2021, 93(34): 11859.
[32]	FARIVAR F, YAP P L, HASSAN K, et al. Unlocking thermogravimetric analysis (TGA) in the fight against “fake graphene” materials. Carbon, 2021, 179: 505.