This is an open access article published under a Creative Commons Attribution (CC-BY) License, which permits unrestricted use, distribution and reproduction in any medium, provided the author and source are cited.
Article Cite This: ACS Omega 2018, 3, 16651−16657
http://pubs.acs.org/journal/acsodf
Nanoporous Nickel Composite Catalyst for the Dry Reforming of Methane Takeshi Fujita,*,† Xiaobo Peng,*,‡ Akira Yamaguchi,§ Yohei Cho,§ Yongzheng Zhang,† Kimitaka Higuchi,∥ Yuta Yamamoto,∥ Tomoharu Tokunaga,∥ Shigeo Arai,∥ Masahiro Miyauchi,*,§ and Hideki Abe*,‡
ACS Omega 2018.3:16651-16657. Downloaded from pubs.acs.org by 46.148.112.157 on 01/22/19. For personal use only.
†
School of Environmental Science and Engineering, Kochi University of Technology, 185 Miyanokuchi, Tosayamada, Kami, Kochi 782-8502, Japan ‡ National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan § School of Materials and Chemical Technology, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8552, Japan ∥ Institute of Materials and Systems for Sustainability, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan S Supporting Information *
ABSTRACT: The development of efficient catalysts with high activities and durabilities for use in the dry reforming of methane (DRM) is desirable but challenging. We report the development of a nanoporous nickel composite (nanoporous Ni/Y2O3) via a facile one-step dealloying technique, for use in the DRM. Focusing on the low-temperature DRM, our composite possessed remarkable activity and durability against coking compared with conventional particle-based Ni catalysts. This was attributed to the aluminum oxides present on the Ni surface, which suppress pore coarsening. In addition, the inert bundled Y2O3 nanowires are suitable for use as substrates for nanoporous Ni.
■
INTRODUCTION As the major components of natural and greenhouse gases, methane (CH4) and carbon dioxide (CO2) are key to achieving a more sustainable society. Accordingly, the dry reforming of methane (DRM) into “syn gas”, which is represented by the transformation CH4 + CO2 → 2H2 + 2CO, could be a potential technological solution; however, this reaction requires high temperatures (550−1000 °C), which results in significant catalyst degradation due to material sintering and coke deposition.1−3 To date, many heterogeneous (typically Ni-based) catalysts have been evaluated to determine their stabilities and performances and the modification of interactions between Ni and oxide supports4−8 and/or the structural design of multicore−shell shaped species9−22 have been proposed. Overall, the enhancement of catalyst performances is the key target, in particular, in the context of lowering reaction temperatures. Dealloying is an electrochemical process commonly employed for the leaching of less noble elements from precursor alloys to form bicontinuous nanoporous materials.23,24 Recently, nanoporous metals with excellent chemical and physical properties have been prepared via dealloying, thereby leading to cross-interdisciplinary research related to batteries, catalysis, sensing, and biotechnological applications.25−30 However, nanopore coarsening at high temper© 2018 American Chemical Society
atures can cause a degradation in performance and the suppression of such coarsening is a challenging issue. We herein report the preparation of nanoporous Ni composites via the one-step dealloying of a NiYAl alloy and compare the DRM performances and durabilities of these composites with those of conventional Ni catalysts prepared via chemical routes. In particular, we focus on the low-temperature DRM (450 °C) where carbon coking tends to be significant for Ni catalysts and we wish to demonstrate that our nanoporous Ni composites exhibit structural durability and resistance to coking. We expect that the nanoporous Ni composites reported herein will widen the application of nanoporous metals and inspire the design of novel DRM catalysts.
■
RESULTS AND DISCUSSION As outlined in Figure 1a, we initially prepared the nanoporous Ni composite catalyst from the dealloying of a precursor alloy by Al leaching using a 30 wt % solution of NaOH, whereas Ni does not dissolve in the strongly alkalic solution. In addition, we compared the performances of products obtained from two precursors, namely, Al4NiY and Al2NiY intermetallics, with Received: August 14, 2018 Accepted: November 20, 2018 Published: December 5, 2018 16651
DOI: 10.1021/acsomega.8b02023 ACS Omega 2018, 3, 16651−16657
ACS Omega
Article
diameter. In addition, X-ray analysis (Figure 1e) confirmed the uniform distribution of Ni and Al. Indeed, the X-ray diffraction (XRD) patterns showed that changes in the crystal structure took place during dealloying, with conversion from the intermetallic Al4NiY precursor to the fcc Ni and Y(OH)3 compounds being followed by the conversion of Y(OH)3 to Y2O3 subsequent to the DRM reaction. This process is outlined in Figure S1. From inductively coupled plasma (ICP) analysis, the nominal elemental composition was determined to be Ni20.8Y19.2Al3.5O 56.5 (atom %). In addition, the Brunauer−Emmett−Teller (BET) surface area was calculated to be 8.3 m2/g. For comparison with conventional catalysts, Ni/Al2O3 and Ni/Y2O3 composites were synthesized via a hydrothermal method and the TEM images of these composites are shown in Figures S2 and S3. For the conventional catalysts, Ni particle sizes were comparable to those of the nanoporous Ni/Y2O3 prepared herein, and to maximize the performance, the volumes of the Ni and oxide components were similar. As shown in Table 1, Figures 2, and S4, the catalytic performances of the prepared composites were examined for
Figure 1. (a) Schematic illustration of the experimental procedure; (b, c) low-magnification TEM images; (d) high-magnification TEM image showing the fine pores; (e) scanning TEM (STEM) image and energy-dispersive X-ray spectrometry (EDS) chemical maps of the selected area, showing the distributions of Ni (red) and Al (green).
Al4NiY being the more desirable of the two, as discussed later. It should be noted here that the nanoporous Ni/Y2O3 refers to the dealloyed Ni12.5Y12.5Al75 (Al4NiY). Thus, we selected the nanoporous Ni composites prepared from the Al4NiY precursor for extensive evaluation. Interestingly, this one-step dealloying procedure employed NiYAl powders to yield bundled urchinlike nanoporous Ni particles bearing yttrium hydroxide, Y(OH)3. Although the tangled urchinlike Y(OH)3 structure was unexpectedly obtained, we do note that hexagonal yttrium hydroxide nanowires have been previously prepared via hydrothermal routes.31 The driving force for growth was attributed to the crystal structure of yttrium hydroxide, and the formation mechanism was attributed to complex interactions between the OH− and Y3+ ions.32 Figure 1b,c shows the low-magnification transmission electron microscopy (TEM) images of the prepared samples, and the high-resolution image given in Figure 1d indicates that the nanoporous Ni regions contain fine pores of ∼10−20 nm
Figure 2. DRM performance plotted against time-on-stream and comparison with conventional Ni/Al2O3. Nanoporous Ni/Y2O3: solid red box, CH4 conversion; solid green box, CO2 conversion; upward solid blue triangle, reactor pressure; Ni/Al2O3: open red ring, CH4 conversion; open green ring, CO2 conversion; upward open blue triangle, reactor pressure.
the DRM over 100 h at 450 °C and the results compared with those of conventional Ni/Al2O3 and Ni/Y2O3. The product obtained from the Ni12.5Y12.5Al75 precursor gave a slightly better performance than that obtained from Ni25Y25Al50, as shown in Table 1, and it was found by ICP analysis that the dealloying of Al was incomplete for the Ni25Y25Al50 precursor (Table S1), thereby suggesting that the Al-rich precursor (Ni12.5Y12.5Al75) preferentially forms the desired nanostructure during the dealloying process. In the initial stages of the reaction, Ni/Al2O3 and Ni/Y2O3 were more active than our
Table 1. DRM Performance of the Ni/Y2O3 Composites Dealloyed from Ni12.5Y12.5Al75 and Ni25Y25Al50 and Compared with the Performances of Ni/Al2O3 and Ni/Y2O3 Prepared via Chemical Routesa samples nanoporous Ni/Y2O3 (Ni12.5Y12.5Al75-dealloyed) nanoporous Ni/Y2O3 (Ni25Y25Al50-dealloyed) Ni/Al2O3 Ni/Y2O3
CH4 conv. (%)
CO2 conv. (%)
CH4 consumpt. rate (10−5 mol h−1)
CO2 consumpt. rate (10−5 mol h−1)
H2 formation rate (10−5 mol h−1)
CO formation rate (10−5 mol h−1)
H2/CO rate
37
37
100
100
197
142
1.4
30
34
80
91
158
141
1.1
54 48
40 36
143 130
106 97
285 255
136 134
2.0 1.9
Measurements were taken at 450 °C after 6 h (from Figure 2).
a
16652
DOI: 10.1021/acsomega.8b02023 ACS Omega 2018, 3, 16651−16657
ACS Omega
Article
prepared samples but both caused significant carbon coking and increased the reactor pressure due to stacking. Indeed, to prevent breakdown of the reactor, it was necessary to terminate the tests after ∼15 h. In contrast, the nanoporous Ni/Y2O3 composite (i.e., dealloyed Ni12.5Y12.5Al75) prepared herein maintained a moderately high performance over 100 h and the reactor pressure remained relatively constant, thereby indicating that carbon coking was suppressed. It should be noted that an ideal equilibrium conversion of 59% was calculated33 for CH4 and CO2 at 450 °C, assuming that no side reactions take place, thereby indicating that there is still scope for further improvement. Coking suppression in the nanoporous Ni/Y2O3 composite was confirmed by in situ Fourier transform infrared (FTIR) experiments, as shown in Figure 3a,b. More specifically, H2 and
Figure 4. TGA analysis of the spent and as-prepared catalysts. Nanoporous Ni/Y2O3 after 6 h at 450 °C and Ni/Al2O3 after 6 h at 450 °C.
from the as-prepared samples that were not subjected to the DRM are also shown. The sharp mass loss above 500 °C corresponds to the combustion of carbon,5,22 thereby indicating that carbon coking is indeed suppressed for the nanoporous Ni/Y2O3. Upon comparison of the heat durability with that of the bare nanoporous Ni dealloyed from a NiMn precursor at 650 °C (Figure S6) in our previous study34 and with that of other bare nanoporous metals, we found that the prepared composite exhibited an excellent durability against heat. To determine the origin of this improved durability, the microstructure of the nanoporous Ni/Y2O3 composite (i.e., dealloyed Ni12.5Y12.5Al75) was examined following the DRM test at 650 °C for 3 h and the duration test at 450 °C for 100 h (Figure 5a,b) and the region of interest in Figure 5b is probed on the nanoporous Ni area that does not contain Y oxide substrate; hence, Y mapping is not shown/detected here. Representative low-magnification images are also shown in Figure S7. In both cases, the nanostructured Ni/Y2O3 with fine nanopores (i.e., ∼20−30 nm diameter) was retained. We also observed slight pore coarsening during the DRM test, which corresponds to the decay taking place during the DRM (Figure 2). Interestingly, energy-dispersive X-ray spectrometry (EDS) mapping clearly indicated that oxides of aluminum were formed on the nanoporous Ni surface and that this suppressed pore coarsening. Indeed, as surface diffusion is the dominant mechanism of pore coarsening, a novel solution for suppressing such surface diffusion involves the formation of a nanometerthick layer of alumina by atomic layer deposition (ALD).35 In this study, the nanostructure transformed into a more active and durable nanostructure without the requirement for the expensive ALD process, as the solid-solute Al (Figure 1e) diffused to the surface and underwent oxidation on the nanoporous Ni. The reaction-driven transformation of porous nanostructures into active nanostructures can also be found in other nanoporous metals36 and intermetallic compounds.37 We subsequently performed the in situ observation of nanoporous Ni/Y2O3 under the DRM reaction atmosphere using TEM with an environmental cell to gain further insight into the resistance of this material to coking. The initial microstructure present prior to the reaction is shown in Figure 6a. Upon increasing the temperature to 600 °C under vacuum, no change in the microstructure was observed. In addition, no carbon coking or pore coarsening was observed for the nanoporous Ni regions following the introduction of a mixture of CH4 and CO2 (see Figure 6b), thereby indicating the
Figure 3. (a) Concentrations of CH4, H2, and CO during the in situ FTIR experiment plotted against the reaction time for the nanoporous Ni/Y2O3. Open red ring, H2; solid green box, CO; and upward solid blue triangle, CH4. (b) FTIR spectra of the nanoporous Ni/Y2O3 and Ni/Al2O3 (Ni) materials.
CO were generated at both 450 and 700 °C without any significant catalytic degradation being observed and the absence of significant signals indicated that little carbon coking took place. However, in the case of the conventional Ni/Al2O3, the presence of abundant absorbance signals between 1000 and 4000 cm−1 was attributed to carbon coking (note that the bands from the CO2 phase at 2360 and 2340 cm−1 are overlapped) and these signals increased in intensity with increasing reaction time. Furthermore, the scanning electron microscopy images confirmed that graphitic carbon nanotubes covered the surface following the FTIR experiments, as shown in Figure S5. The deposited carbon present following the DRM process was also evaluated by thermal gravimetric differential thermal analysis (TG-DTA) under ambient conditions. The mass differences between the nanoporous Ni/Y2O3 (i.e., dealloyed Ni12.5Y12.5Al75) and the conventional Ni/Al2O3 samples after the DRM are shown in Figure 4. For comparison, the data 16653
DOI: 10.1021/acsomega.8b02023 ACS Omega 2018, 3, 16651−16657
ACS Omega
Article
Figure 5. STEM image and EDS chemical maps of the selected area, showing the elemental distributions after the DRM tests of the nanoporous Ni/Y2O3 composite (i.e., dealloyed Ni12.5Y12.5Al75): (a) 650 °C for 3 h and (b) 450 °C for 100 h.
Ni could be key to understanding the improved coking resistance. In addition, although we presume the formation of a complex mixture between the carbon layer and the Y2O3 surface during in situ observation of nanoporous Ni/Y2O3 under the DRM reaction atmosphere, as indicated in Figures 6d,e and S9 showing the layer-by-layer motion and the tubelike feature, the whole Y2O3 substrate was stable, which was also confirmed in the practical DRM tests (Figure S7). The structurally robust nature of the inert Y2O3 wire may also account for the improved heat durability, thereby rendering this a suitable substrate for nanoporous Ni.
■
CONCLUSIONS In summary, we successfully developed a nanoporous Ni/Y2O3 catalyst for use in the dry reforming of methane (DRM). This nanoporous nickel composite was prepared via a one-step dealloying process, and the aluminum oxide from the solidsolute Al present on the nanoporous Ni surface was found to be key to understanding the structural stability of the catalyst against heat and coking, due to its role in preventing pore coarsening. We found that the inert and urchinlike bundled Y2O3 was a suitable and robust substrate for nanoporous Ni. As we expect that the production of these nanoporous catalysts could easily be scaled up, they can be considered a potential alternative to traditional Ni particle catalysts for application in the DRM and may inspire the design of novel DRM catalysts.
Figure 6. In situ TEM observations during the DRM reaction at 600 °C. (a) Low-magnification TEM image and the region of interest, as marked. (b) Region of nanoporous Ni showing the least amount of coking after 5 min. Growth of the carbon layer on Y2O3: (c) the initial stage and after (d) 2 min and (e) 5 min.
improved coking resistance of the nanoporous structure compared to that of the Ni particles. In the case of conventional Ni particles, carbon deposition and nanotube growth were catalytically triggered on the Ni surface38,39 during in situ TEM observations of the conventional Ni/Al2O3 catalyst (see Figure S8). It therefore appears that the high structural stability of the aluminum oxide-coated nanoporous
■
METHODS Preparation of Nanoporous Metals. Nanoporous Ni Composite. Ni12.5Y12.5Al75 and Ni25Y25Al50 (atom %) ingots were prepared by melting pure Ni, Y, and Al (purity >99.9 16654
DOI: 10.1021/acsomega.8b02023 ACS Omega 2018, 3, 16651−16657
ACS Omega
Article
atom %), using an Ar-protected arc melting furnace, where Ni12.5Y12.5Al75 was the optimal composition for dealloying. The prepared ingots were ground using a mortar and pestle and then sieved to obtain powdered samples with an average size of 20 μm. The precursor powders were dealloyed in a 30 wt % NaOH (97% Wako, Japan) solution for 4 h at 50 °C and then rinsed thoroughly with water and dried under air. Conventional Ni/Al2O3 and Ni/Y2O3 Composites. The Ni/ Al2O3 and Ni/Y2O3 composites were prepared by a conventional impregnation method. More specifically, following the dissolution of Ni(NO3)2·6H2O (0.8 g, Sigma-Aldrich) in ethanol (20 mL), either Al2O3 (0.3 g, Sigma-Aldrich) or Y2O3 (0.3 g, Sigma-Aldrich) powder was added to the alcoholic solution. The resulting mixture was stirred for 8 h, and then ethanol was removed by evaporation at 353 K. The desired Ni/ Al2O3 and Ni/Y2O3 catalysts were obtained following calcination in a H2−Ar gas mixture (5 vol % H2) at 873 K over 4 h. Microstructural Characterization. The microstructures of the obtained catalysts were characterized by transmission electron microscopy (TEM, JEM-2100F, JEOL, equipped with aberration correctors, for the image- and probe-forming lens systems, CEOS GmbH) and energy-dispersive X-ray spectrometry (EDS, JED-2300T, JEOL). High-resolution TEM and scanning TEM (STEM) observations were conducted at an accelerating voltage of 200 kV, with the Cs correctors optimized for point-to-point resolutions of 1.3 and 1.1 Å for TEM and STEM, respectively. The samples were transferred onto a Cu grid without the use of a uniform carbon support film. X-ray diffraction profiles were obtained using a Rigaku SmartLab X-ray diffractometer with Cu Kα radiation. For in situ TEM analyses, a 1000 kV JEM-1000K RS TEM (JEOL) equipped with an environmental cell designed at Nagoya University (Japan) was employed, along with a pointto-point resolution of 1.5 Å. All samples were observed in a CH4 + CO2 gas mixture (50:50, vol %) at 600 °C over a wide range of total pressures (1−30 Pa). The current flux was measured as 0.23 A cm−2 using a Faraday gauge. Inductively coupled plasma analysis was performed using an IRIS Advantage DUO instrument (Thermo Fisher Scientific). The deposited carbon present after the DRM process was evaluated by using thermal gravimetric differential thermal analyzer (TG-DTA, NETZCH, STA 2500) under air. The sharp mass loss above 500 °C corresponded to the combustion of carbon. Catalytic Experiments. The desired sample (100 mg) was loaded into a 4 mm quartz tube and tested using a continuousflow fixed-bed microreactor under atmospheric pressure. The quantities of CH4, CO, H2, and CO2 were monitored and evaluated using an on-line gas analyzer (BELMass, MicrotracBEL) and a gas chromatograph (GC-2014, Shimadzu, Japan) equipped with thermal conductivity detectors. The reactant gas containing 1 vol % CH4, 1 vol % CO2, and Ar for balance was introduced into the reactor at a space velocity of 100 cm3 min−1 (W/F = 0.06 g s cm−3). The calculation details for the DRM performance are as follows CH4 conv. [%] =
[CH4]in − [CH4]out [CH4]in
CO2 conv. [%] =
[CO2 ]in − [CO2 ]out [CO2 ]in
CH4 consumption rate = [CH4]in flow rate × CH4 conv. [%] CO2 consumption rate = [CO2 ]in flow rate × CO2 conv. [%] H 2 formation rate = [CH4]in flow rate ×
[H 2]out [CH4]in
CO formation rate = ([CH4]in flow rate + [CO2 ]in flow rate) [CO]out × [CH4]in + [CO2 ]in H 2 /CO ratio =
H 2 formation rate CO formation rate
where [...]in and [...]out represent the gas concentrations in the feed gas and effluent gas, respectively. FTIR spectra of the catalyst surfaces were measured at the operating temperature using a JASCO 6100 FTIR system equipped with a heat chamber (ST-Japan). Each sample (5 mg) was loaded onto the sample stage, and the reactant gas containing 1 vol % CH4, 1 vol % CO2, and Ar for balance was introduced into the environmental cell at a rate of 10 cm3 min−1. The concentrations of the feed gas and generated gas components were determined using micro gas chromatography (Inficon, 3000 Micro-GC). Surface Area Measurements. The Brunauer−Emmett− Teller (BET) surface areas of the samples were measured at 77 K using a BELSORP-MAX II (MicrotracBEL Japan, Inc.). Each sample was heated at 80 °C under vacuum for 24 h prior to measurement, and the mass of each sample was measured using a balance.
■
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsomega.8b02023.
■
TEM and XRD results and comparison of catalyst performances (PDF)
AUTHOR INFORMATION
Corresponding Authors
*E-mail: *E-mail: *E-mail: *E-mail:
[email protected] (T.F.).
[email protected] (X.P.).
[email protected] (M.M.).
[email protected] (H.A.).
ORCID
Takeshi Fujita: 0000-0002-2318-0433 Akira Yamaguchi: 0000-0002-3550-4239 Masahiro Miyauchi: 0000-0001-8889-2645 Hideki Abe: 0000-0002-8392-7586 Notes
The authors declare no competing financial interest. 16655
DOI: 10.1021/acsomega.8b02023 ACS Omega 2018, 3, 16651−16657
ACS Omega
■
Article
(16) Li, Z.; Kawi, S. Multi-Ni@Ni phyllosilicate hollow sphere for CO2 reforming of CH4: influence of Ni precursors on structure, sintering, and carbon resistance. Catal. Sci. Technol. 2018, 8, 1915− 1922. (17) Li, Z.; Das, S.; Hongmanorom, P.; Dewangan, N.; Wai, M. H.; Kawi, S. Silica-based micro- and mesoporous catalysts for dry reforming of methane. Catal. Sci. Technol. 2018, 8, 2763−2778. (18) Li, Z.; Wang, Z.; Jiang, B.; Kawi, S. Sintering resistant Ni nanoparticles exclusively confined within SiO2 nanotubes for CH4 dry reforming. Catal. Sci. Technol. 2018, 8, 3363−3371. (19) Li, Z.; Yang, J.; Agyeman, D. A.; Park, M.; Tamakloe, W.; Yamauchi, Y.; Kang, Y.-M. CNT@Ni@Ni−Co silicate core−shell nanocomposite: a synergistic triple-coaxial catalyst for enhancing catalytic activity and controlling side products for Li−O2 batteries. J. Mater. Chem. A 2018, 6, 10447−10455. (20) Li, Z.; Sibudjing, K. Facile synthesis of multi-Ni-core@Ni phyllosilicate@CeO2 shell hollow spheres with high oxygen vacancy concentration for dry reforming of CH4. ChemCatChem 2018, 10, 2994−3001. (21) Kathiraser, Y.; Wang, Z.; Ang, M. L.; Mo, L.; Li, Z.; Oemar, U.; Kawi, S. Highly active and coke resistant Ni/SiO2 catalysts for oxidative reforming of model biogas: Effect of low ceria loading. J. CO2 Util. 2017, 19, 284−295. (22) Das, S.; Ashok, J.; Bian, Z.; Dewangan, N.; Wai, M. H.; Du, Y.; Borgna, A.; Hidajat, K.; Kawi, S. Silica−Ceria sandwiched Ni core− shell catalyst for low temperature dry reforming of biogas: Coke resistance and mechanistic insights. Appl. Catal., B 2018, 230, 220− 236. (23) Forty, A. J. Corrosion micro-morphology of noble-metal alloys and depletion gilding. Nature 1979, 282, 597−598. (24) Erlebacher, J.; Aziz, M. J.; Karma, A.; Dimitrov, N.; Sieradzki, K. Evolution of nanoporosity in dealloying. Nature 2001, 410, 450− 453. (25) Qiu, H. J.; Kang, J. L.; Liu, P.; Hirata, A.; Fujita, T.; Chen, M. W. Fabrication of large-scale nanoporous nickel with a tunable pore size for energy storage. J. Power Source 2014, 247, 896−905. (26) Qiu, H. J.; Li, X.; Xu, H. T.; Zhang, H. J.; Wang, Y. Nanoporous metal as a platform for electrochemical and optical sensing. J. Mater. Chem. C 2014, 2, 9788−9799. (27) Qiu, H. J.; Xu, H. T.; Liu, L.; Wang, Y. Correlation of the structure and applications of dealloyed nanoporous metals in catalysis and energy conversion/storage. Nanoscale 2015, 7, 386−400. (28) Fujita, T. Hierarchical nanoporous metals as a path toward the ultimate three-dimensional functionality. Sci. Technol. Adv. Mater. 2017, 18, 724−740. (29) Ding, Y.; Chen, M. W. Nanoporous metals for catalytic and optical applications. MRS Bull. 2009, 34, 569−576. (30) Ito, Y.; Tanabe, Y.; Sugawara, K.; Koshino, M.; Takahashi, T.; Tanigaki, K.; Aoki, H.; Chen, M. Three-dimensional porous graphene networks expand graphene-based electronic device applications. Phys. Chem. Chem. Phys. 2018, 20, 6024−6033. (31) Li, N.; Yanagisawa, K. Yttrium Oxide Nanowires, Nanowires Nicoleta Lupu; IntechOpen, 2010. (32) Li, Q.; Caihong, F.; Qingze, J.; Lin, G.; Chenmin, L.; Bin, X. H. Shape-controlled synthesis of yttria nanocrystals under hydrothermal conditions. Phys. Status Solidi A 2004, 201, 3055−3059. (33) Gordon, S.; McBride, B. J. Computer Program for Calculation of Complex Chemical Equilibrium Compositions and Applications; NASA Reference Publication 1311, 1996. (34) Fujita, T.; Higuchi, K.; Yamamoto, Y.; Tokunaga, T.; Arai, S.; Abe, H. In-situ TEM study of a nanoporous Ni−Co catalyst used for the dry reforming of methane. Metals 2017, 7, No. 406. (35) Biener, M. M.; Biener, J.; Wichmann, A.; Wittstock, A.; Baumann, T. F.; Baumer, M.; Hamza, A. V. ALD Functionalized nanoporous gold: Thermal stability, mechanical properties, and catalytic activity. Nano Lett. 2011, 11, 3085−3090. (36) Fujita, T.; Abe, H.; Tanabe, T.; Ito, Y.; Tokunaga, T.; Arai, S.; Yamamoto, Y.; Hirata, A.; Chen, M. W. Earth-abundant and durable
ACKNOWLEDGMENTS This study was mainly supported by the JST-CREST program “Innovative catalysts and creation technologies for the utilization of diverse natural carbon resources” (grant No. JPMJCR15P1) and was partially supported by KAKENHI (grant No. JP16H02293). We also acknowledge support from the Advanced Characterization Nanotechnology Platform of the High-Voltage Electron Microscope Laboratory at Nagoya University and Prof. Mingwei Chen for the use of TEM at Tohoku University. The authors thank Kazuyo Omura of the Institute for Material Research at Tohoku University for carrying out the XPS measurements and Kazu Takeda at the Tokyo Institute of Technology for his contributions to the measurement of the in situ FTIR spectra.
■
REFERENCES
(1) Muraza, O.; Galadima, A. A review on coke management during dry reforming of methane. Int. J. Energy Res. 2015, 39, 1196−1216. (2) Nair, M. M.; Kaliaguine, S. Structured catalysts for dry reforming of methane. New J. Chem. 2016, 40, 4049−4060. (3) Lavoie, J. M. Review on dry reforming of methane, a potentially more environmentally-friendly approach to the increasing natural gas exploitation. Front. Chem. 2014, 2, No. 81. (4) Kathiraser, Y.; Thisartarn, W.; Sutthiumporn, K.; Kawi, S. Inverse NiAl2O4 on LaAlO3−Al2O3: Unique catalytic structure for stable CO2 reforming of methane. J. Phys. Chem. C 2013, 117, 8120− 8130. (5) Ashok, J.; Bian, Z.; Wang, Z.; Kawi, S. Ni-phyllosilicate structure derived Ni−SiO2−MgO catalysts for bi-reforming applications: Acidity, basicity and thermal stability. Catal. Sci. Technol. 2018, 8, 1730−1742. (6) Ni, J.; Chen, L.; Lin, J.; Kawi, S. Carbon deposition on borated alumina supported nano-sized Ni catalysts for dry reforming of CH4. Nano Energy 2012, 1, 674−686. (7) Gao, X. Y.; Hidajat, K.; Kawi, S. Facile synthesis of Ni/SiO2 catalyst by sequential hydrogen/air treatment: A superior anti-coking catalyst for dry reforming of methane. J. CO2 Util. 2016, 15, 146−153. (8) Kathiraser, Y.; Wang, Z.; Ang, M. L.; Mo, L.; Li, Z.; Oemar, U.; Kawi, S. Highly active and coke resistant Ni/SiO2 catalysts for oxidative reforming of model biogas: Effect of low ceria loading. J. CO2 Util. 2017, 19, 284−295. (9) Li, Z.; Kathiraser, Y.; Kawi, S. Facile Synthesis of High Surface Area Yolk−Shell Ni@Ni Embedded SiO2 via Ni Phyllosilicate with Enhanced Performance for CO2 Reforming of CH4. ChemCatChem 2015, 7, 160−168. (10) Bian, Z.; Kawi, S. Sandwich-like silica@Ni@silica multicore− shell catalyst for the low-temperature dry reforming of methane: Confinement effect against carbon formation. ChemCatChem 2018, 10, 320−328. (11) Li, Z.; Mo, L.; Kathiraser, Y.; Kawi, S. Yolk−satellite−shell structured Ni−yolk@Ni@SiO2 nanocomposite: Superb catalyst toward methane CO2 reforming reaction. ACS Catal. 2014, 4, 1526−1536. (12) Li, Z.; Kathiraser, Y.; Ashok, J.; Oemar, U.; Kawi, S. Simultaneous Tuning Porosity and Basicity of Nickel@Nickel− Magnesium Phyllosilicate Core−Shell Catalysts for CO2 Reforming of CH4. Langmuir 2014, 30, 14694−14705. (13) Bian, Z.; Suryawinata, I. Y.; Kawi, S. Highly carbon resistant multicore-shell catalyst derived from Ni-Mg phyllosilicate nanotubes@silica for dry reforming of methane. Appl. Catal., B 2016, 195, 1−8. (14) Li, Z.; Li, M.; Bian, Z.; Kathiraser, Y.; Kawi, S. Design of highly stable and selective core/yolk−shell nanocatalystsA review. Appl. Catal., B 2016, 188, 324−341. (15) Li, Z. W.; Jiang, B.; Wang, Z. G.; Kawi, S. High carbon resistant Ni@Ni phyllosilicate@SiO2 core shell hollow sphere catalysts for low temperature CH4 dry reforming. J. CO2 Util. 2018, 27, 238−246. 16656
DOI: 10.1021/acsomega.8b02023 ACS Omega 2018, 3, 16651−16657
ACS Omega
Article
nanoporous catalyst for exhaust-gas conversion. Adv. Funct. Mater. 2016, 26, 1609−1616. (37) Tanabe, T.; Imai, T.; Tokunaga, T.; Arai, S.; Yamamoto, Y.; Ueda, S.; Ramesh, G. V.; Nagao, S.; Hirata, H.; Matsumoto, S.; Fujita, T.; Abe, H. Nanophase-separated Ni3Nb as an automobile exhaust catalyst. Chem. Sci. 2017, 8, 3374−3378. (38) Rodríguez-Manzo, J. A.; Terrones, M.; Terrones, H.; Kroto, H. W.; Sun, L.; Banhart, F. In situ nucleation of carbon nanotubes by the injection of carbon atoms into metal particles. Nat. Nanotechnol. 2007, 2, 307. (39) Zhang, L.; Hou, P.-X.; Li, S.; Shi, C.; Cong, H.-T.; Liu, C.; Cheng, H.-M. In Situ TEM observations on the sulfur-assisted catalytic growth of single-wall carbon nanotubes. J. Phys. Chem. Lett. 2014, 5, 1427−1432.
16657
DOI: 10.1021/acsomega.8b02023 ACS Omega 2018, 3, 16651−16657
