Oxidative Dehydrogenation on Nanocarbon - American Chemical

Article Cite This: Acc. Chem. Res. XXXX, XXX, XXX−XXX

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Oxidative Dehydrogenation on Nanocarbon: Insights into the Reaction Mechanism and Kinetics via in Situ Experimental Methods Wei Qi,*,†,‡ Pengqiang Yan,†,‡ and Dang Sheng Su*,†,§ †

Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, P. R. China ‡ University of Chinese Academy of Sciences, Beijing 100049, P. R. China § Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, P. R. China CONSPECTUS: Sustainable and environmentally benign catalytic processes are vital for the future to supply the world population with clean energy and industrial products. The replacement of conventional metal or metal oxide catalysts with earth abundant and renewable nonmetallic materials has attracted considerable research interests in the field of catalysis and material science. The stable and efficient catalytic performance of nanocarbon materials was discovered at the end of last century, and these materials are considered as potential alternatives for conventional metal-based catalysts. With its rapid development in the past 20 years, the research field of carbon catalysis has been experiencing a smooth transition from the discovery of novel nanocarbon materials or related new reaction systems to the atomistic-level mechanistic understanding on the catalytic process and the subsequent rational design of the practical catalytic reaction systems. In this Account, we summarize the recent progress in the kinetic and mechanistic studies on nanocarbon catalyzed alkane oxidative dehydrogenation (ODH) reactions. The paper attempts to extract general concepts and basic regularities for carbon catalytic process directing us on the way for rational design of novel efficient metal-free catalysts. The nature of the active sites for ODH reactions has been revealed through microcalorimetric analysis, ambient pressure X-ray photoelectron spectroscopy (XPS) measurement, and in situ chemical titration strategies. The detailed kinetic analysis and in situ catalyst structure characterization suggests that carbon catalyzed ODH reactions involve the redox cycles of the ketonic carbonyl−hydroxyl pairs, and the key physicochemical parameters (activation energy, reaction order, and rate/ equilibrium constants, etc.) of the carbon catalytic systems are proposed and compared with conventional transition metal oxide catalysts. The proposal of the intrinsic catalytic activity (TOF) provides the possibility for the fair comparisons of different nanocarbon catalysts and the consequent structure−function relation regularity. Surface modification and heteroatom doping are proved as the most effective strategies to adjust the catalytic property (activity and product selectivity etc.) of the nanocarbon catalysts. Nanocarbon is actually a proper candidate platform helping us to understand the classical catalytic reaction mechanism better, since there is no lattice oxygen and all the catalytic process happens on nanocarbon surface. This Account also exhibits the importance of the in situ structural characterizations for heterogeneous nanocarbon catalysis. The research strategy and methods proposed for carbon catalysts may also shed light on other complicated catalytic systems or fields concerning the applications of nonmetallic materials, such as energy storage and environment protection etc. dehydrogenation of alkanes,5 selective oxidation of organics,6 hydrogenation,7 hydrohalogenation,8,9 electrochemical reactions, etc.10 However, in-depth mechanistic research has grown slowly compared with the unparalleled development of novel nanocarbon catalytic materials and their applications in new reaction systems.5 There is an urgent demand for understanding the nature of the carbon catalytic process and also the establishment of fundamental theory for carbon catalysis. In this Account, we summarize current mechanistic understandings of the carbon catalytic process with alkane oxidative

1. INTRODUCTION The modern green chemical industry has made urgent and strict demands on environmental protection and sustainable development, which has seriously restricted the large scale applications of conventional metal-based catalysts, especially precious metal and toxic metal oxides. Earth abundant and renewable carbon materials are normally applied as catalyst supports, but in fact they are not completely chemically inert. Carbon was first found to exhibit catalytic activity in alkane dehydrogenation reactions in the 1970s,1 and the rapid development of nanocarbon materials at the end of last century provides ideal platforms for catalysis.2−4 The tunable surface functionalities and the relatively large π-conjugation systems provide nanocarbon materials stable catalytic activity in © XXXX American Chemical Society

Received: September 27, 2017

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DOI: 10.1021/acs.accounts.7b00475 Acc. Chem. Res. XXXX, XXX, XXX−XXX

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Accounts of Chemical Research

Figure 1. (a) Differential adsorption heats of propane on CNT catalysts as a function of surface coverage. (b) In situ O 1s XPS spectra of working CNT catalysts (375 °C, 0.25 mbar butane and O2). (c) Schematic drawings of the chemical titration process for oxygen functionalities on CNTs. (d) EB ODH conversion rates of o-CNTs, o-CNT titration derivatives and CNTs with only defects. Adapted with permission from refs 25 and 26 (copyright 2011 and 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) and from ref 19 (copyright 2008 American Association for the Advancement of Science).

ization strategies are extremely important in revealing the nature of carbon catalysis and are also introduced in present paper. The generally accepted concepts or basic regularities for carbon catalytic process from the mechanistic view will be extracted and summarized, which sheds light on the rational design of novel efficient metal-free catalytic systems.

dehydrogenation (ODH) reactions as an example. Alkane ODH (producing alkenes) is recognized as not only an important type of reaction from the viewpoint of the chemical industry but also one of the carbon catalyzed reactions that has been studied earliest and most thoroughly. Drago and Jurczyk systematically evaluated the catalytic properties of activated carbon in ethylbenzene (EB) ODH reactions in 1990s,11 and at almost the same time, Figueiredo’s group found that oxygen functionalities on activated carbon and carbon nanofiber (CNF) are possible active sites for alkane ODH reactions.12 Schlögl and co-workers reported the first example using oxidized carbon nanotubes (CNTs) and onion-like carbon (OLC) as catalysts in EB ODH reactions in 2000.13 These materials have ordered sp2 hybridized graphitic structure, which could inhibit coke formation and exhibit long-term catalytic activity. After that, various novel nanocarbon materials, including mesoporous carbon,14 ultradispersed nanodiamond (ND),15 and graphene (G) or graphene oxides (GO),16−18 have been utilized in alkane ODH reactions, and many encouraging catalytic activity results have been reported even comparable to industrial catalysts.19 This Account will focus on the latest development in the mechanistic and kinetic understandings on carbon catalyzed alkane ODH reactions, including active site identification and quantification, reaction kinetics and mechanism, basic structure−performance relations, and similarity and differences between nanocarbon and transition metal oxide catalysts. Some new in situ character-

2. ACTIVE SITES Identification and quantification of the active sites are the basic requirements for detailed mechanistic understandings of the catalytic process,20 and it is also the most difficult part because of the surface complexity of carbon materials.21 DFT calculation results indicate that quinone or ketonic carbonyl groups exhibit the highest basicity and nucleophilicity compared with other oxygen functionalities (such as carboxylic acid) on nanocarbon,22 preferentially react with saturated C−H bonds, and are first assumed to be the active sites for alkane ODH, and the hypothesis was supported by the experimental observations that model carbon catalysts (phenanthrenequinone cyclotrimer) containing only quinoidic carbonyl groups exhibit catalytic activity in alkane ODH reactions.23 Temperature-programmed desorption (TPD) measurements on activated carbon catalysts before and after EB ODH reactions suggest that the styrene formation rates exhibit first order dependence on the surface concentration of ketonic carbonyl groups.12 For nanocarbon catalysts, it is found first that EB consumption shows positive linear dependence, while styrene B


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Figure 2. (a) EB conversion (square) and titrant uptake (triangle) as a function of time on stream during the steady state activity measurement and in situ titration process. (b) EB conversion rate as a function of the cumulative consumption of PH titrants. Adapted with permission from ref 28. Copyright 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Figure 3. (a) Schematic drawings of the synthesis procedure for model carbon catalysts (YPB-x). (b) ODH rate as a function of EB (circle) and O2 (triangle) partial pressure. (c) ODH rates with C8H10(EB)/O2 (empty triangle) and C8D10(deuterated EB)/O2 (empty circle) on model catalysts. Adapted with permission from ref 31. Copyright 2017 American Chemical Society.

temperature (375 °C). The relative amount of phenolic hydroxyl and ketonic carbonyl groups (reflected by their intensity ratio (I(C−O)/I(CO)) increased from 0.72 to 1.87 after switching off the oxygen, indicating that these two groups are important constituents for alkane ODH reactions. The accurate quantification of the ODH active sites on nanocarbon is an intricate or sometimes impossible task with conventional XPS or TPD methods,24 since the surface functionalities normally exhibit similar physicochemical properties (binding energy, desorption, or decomposition temperature) and the deconvolution of the superimposed XPS or TPD signals is a very complex process. In view of the quantification methods in organic chemistry,27 we have proposed a chemical titration method to determine the surface concentration of three kinds of typical oxygen functional groups (−CO, −C− OH, and −COOH) on nanocarbon surface.26 As shown in Figure 1c, the oxygen functionalities on CNTs could be selectively removed or covered by small organic molecules (titrants) via selective reactions, and the surface concentration of these could be calculated via monitoring the consumption of

selectivity shows negative linear dependence on the total oxygen content of CNTs.24 Microcalorimetric analysis (MCA) running under reaction conditions could provide an overview of the identity of the ODH active sites.25 Figure 1a shows the typical adsorption heat measurement results (heat as a function of surface coverage) of propane on CNTs. Combining the calorimetric measurement (both propane and propylene) and the surface oxygen functionality quantification results with TPD and X-ray photoelectron spectroscopy (XPS), the adsorption sites on oxidized CNTs for propane or propylene molecules are determined as ketonic carbonyl, carboxylic anhydride, lactone/hydroxyl groups, and basal planes of graphitic carbons.25 The ketonic carbonyl groups exhibit the highest adsorption heat and capacity for both propane and propene molecules and may serve as active sites for ODH reactions.25 Another intuitive evidence on the identity of the active sites is provided with in situ ambient pressure XPS analysis.19 As shown in Figure 1b, O 1s XPS of CNT catalysts was measured in the presence of butane and oxygen (0.25 mbar, 1:0 and 1:1) at reaction C


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Figure 4. (a) In-situ IR spectra of model carbon catalysts upon the introduction of EB as a function of the reaction time (fresh polymers as background). (b) In-situ IR spectra and (c) MS signal of reduced model catalysts upon the introduction of O2 or 18O2 as a function of reaction time (reduced polymers as background). 583 K, 1.6 kPa EB, 1.0 kPa O2, balance He, 5 mg catalyst. Adapted with permission from ref 31. Copyright 2017 American Chemical Society.

only ketonic carbonyl groups at their periphery (Figure 3a). The abundance of active sites (ketonic carbonyl group content from 1% to 7.4%) and the surface area (from 560 to 1450 m2g−1) of the model catalysts could be adjusted through controlling the ratio of the precursors,29 which is comparable to typical nanocarbon materials (normally 2−10% oxygen content and 500−1000 m2 g−1). It is interesting to find that the number of active sites from titration could be sometimes slightly lower (∼5%) than the total amount of oxygen species on the catalyst surface. This observation should be caused by steric hindrance and the limitations of particular reaction conditions, which illustrates the importance of in situ structural analysis for carbon catalysts. ODH rate increased monotonically with increasing EB partial pressure, while it reached constant values at oxygen pressures higher than 1 kPa (Figure 3b), suggesting that O2 has limited influence on reaction rates in this kinetic region. The observed kinetic response on EB and O2 partial pressure is consistent with kinetic isotope effect (KIE) results (Figure 3c) showing that the reaction is kinetically controlled by the C−H activation process, namely, the breaking of C−H bond is the rate-determining step (RDS) over a relatively wide alkane/O2 ratio range. One of the key advantages of the model carbon catalysts is their controllable degree of conjugation size providing enough spectroscopic transparency for in situ IR analysis. As shown in Figure 4a, introducing EB alone (in the absence of O2) would lead to a sharp decrease of the IR signal belonging to CO (1690 cm−1). At the same time, the −C−O−H signal (3532 cm−1) increased, suggesting the reduction of the carbon catalysts by EB. The product styrene was simultaneously detected by mass spectroscopy (MS) that connected to the IR spectrometer, indicating that EB could be dehydrogenated even in the absence of O2. The reduced carbon catalysts got reoxidized rapidly after O2 was introduced into the reaction system (Figure 4b). It should be noted that sometimes the spectra are not fully reversible after one reduction−reoxidation cycle, indicating that carbon catalysts may experience irreversible reduction under particular reaction conditions, but the basic structure of the model carbon catalysts, such as the oxygen content and the polymer skeleton, remains identical after the catalytic reaction.29 The quite similar formation rate of H216O and H218O and the observation of 18O16O in the product during isotopic 18O2 reoxidation reactions (Figure 4c) indicated that oxygen molecules may need to be dissociated (activated) on the carbon surface, and this dissociative adsorption may be a reversible process.

the titrants. As shown in Figure 1d, the ketonic carbonyl groups are the only active sites, and the hydroxyl or carboxylic acid groups do not show obvious direct effects in EB ODH reactions through comparing the catalytic activities of various titration derivatives.26 The chemical titration strategy could provide the absolute value of the surface concentration of oxygen functionalities, which avoids the subjectivity caused by the deconvolution and peak identification process in conventional spectroscopic analysis. It should be mentioned that the proper choice of the titrants is the key for accurate quantification of the active sites. For example, phenyl hydrazine (PH) is chosen as titrant because it has similar size and polarity as reactant EB, and the titrated concentration may indicate the number of sites that are accessible and catalytically active in EB ODH reactions. The in situ active site titration was realized to meet the requirements for practical kinetic analysis, and in this way, the intrinsic catalytic activity (turnover frequency, TOF) of nanocarbon catalysts could be obtained from single measurement.28 As shown in Figure 2a, the titrant PH was introduced in situ into the reactor when EB ODH reactions reached steady state. The catalytic activity of CNT decreases monotonically with increasing PH uptake (Figure 2b), and the linear dependence suggests that it is a site-by-site titration process. The slope of the line represents EB conversion rate normalized by the number of the active sites (TOF), which is the foundation for kinetic studies and fair comparison and evaluation of the catalytic activity of carbon catalysts.

3. REACTION KINETICS AND MECHANISM It has been first found that EB conversion on activated carbon could be described by a kinetic model in which the main reaction occurs by a redox mechanism involving quinone/ hydroquinone groups.29 Coke will form on activated carbon during the reaction, and it may serve as new active sites, which also needs to be taken into account in the kinetic model. Nanocarbon materials exhibit higher stability than amorphous activated carbon catalysts.30 The reaction orders with respect to oxygen and EB and the apparent activation energy for different nanocarbon catalysts (CNT, OLC, and ND) are similar (0.3, 0.5, and 73 kJ mol−1, respectively),9 indicating that the same reaction pathway involving the same active sites occurs on these nanocarbon catalysts. Based on the in situ site titration strategy, we performed EB ODH kinetic measurements on model carbon catalysts to reveal the reaction mechanism.31 The model carbon catalysts were synthesized by a polymerization method and contained D


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Accounts of Chemical Research Scheme 1. Schematic Drawings of Alkane ODH Reaction Mechanism for (a) Nanocarbon and (b) V2O5 Catalysts

Figure 5. Schematic and TEM images (a) and ODH catalytic activity (b) for various nanocarbon catalysts (G, graphene; CNT, carbon nanotube, OLC, onion-like carbon). EB conversion (bar) and conversion rate normalized by oxygen content (square, 10−7 molecules EB O−1 s−1), surface area (circle, 10−4 molecules EB nm−1 s−1), and number of active sites (triangle, TOF, 10−4 molecules EB CO−1 s−1), respectively. (c) The excess surface energy as a function of the radius of nanocarbon. Adapted with permission from ref 28 (copyright 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) and from ref 36 (copyright 2010 American Physical Society).

sequentially in consideration of the reaction stoichiometry. It has to be pointed out that Scheme 1a only summarizes the possible catalytic reaction pathway but not the exact chemical structures of the reaction intermediates. For example, the configuration of the intermediate of activated O2 remains unknown, and there is also argument about the direct reoxidation process via gas-phase O2 molecules (forming H2O2 as product) predicted by theoretical calculations.32 In any case, defects and edges of graphene layers are quite active in reacting with oxygen molecules,33 and the chemical nature and reactivity of the adsorbed oxygen are different depending on their location and structure,34 which plays a significant role in determining the product selectivity in light alkane ODH reactions.35

Gathering the titration results, kinetic data, KIE results, and in situ IR measurement results, a plausible reaction mechanism for carbon catalyzed alkane ODH is proposed and compared with typical Mars−van Krevelen mechanism on V2O5 catalysts (Scheme 1a,b). The substrate alkane first adsorbs on ketonic carbonyl groups (O*) on nanocarbon through quasi-equilibrated steps. The irreversible sequent abstraction of the two hydrogen atoms from ethyl groups yields adsorbed alkene and reduced catalysts with hydroxyl groups (OH*). Desorption of alkene was proven to be a fast process. An oxygen molecule may need to be first activated (dissociated) on the carbon catalyst surface forming radical oxygen species through reversible steps. The activated oxygen species reoxidize the active sites under the reduced state (hydroxyl groups) E


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4. STRUCTURE−PERFORMANCE REGULARITIES The kinetic analysis allows us to compare the ODH catalytic activity of carbon materials accurately and fairly, yielding the basic structure−performance regularities. The influence of the macroscopic morphology on the ODH catalytic activity is shown in Figure 5a,b. The selected nanocarbon catalysts possess various structural and physicochemical parameters, and their apparent catalytic activity (ODH rates normalized by catalyst weight, surface area, or oxygen content) exhibits an irregular trend, but the intrinsic catalytic activities (TOF) for them are identical under the same reaction conditions.28 The phenomenon suggests that the chemical nature of the active sites on various nanocarbons are similar. The macroscopic structure (the surface area, morphology, and graphene curvature) exhibits limited influence on their intrinsic activity, at least in this size range (the diameter of the curved graphene layer is above 5 nm). Independent theoretical calculation results have shown that the “total curvature energy”, which is defined as the excess (the increased) surface energy of the curved graphene (such as fullerene) with respect to planar one, exhibits negative linear dependence on the diameter of nanocarbon (Figure 5c), and the influence of curvature is negligible (total curvature energy 98%),45 which is similar to carbon catalysts, and the related research for ultrahigh alkene selectivity may be one of the most important new growth point in nonmetallic catalysis. In addition, nanocarbon has higher surface content of active sites, surface area and lower density than supported transition metal oxide compounds, which could also benefit the catalytic process.

6. CONCLUSIONS AND PERSPECTIVES In conclusion, the present Account provided an overview of the recent progress in the kinetic and mechanistic studies on G


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(3) Chen, D.; Holmen, A.; Sui, Z.; Zhou, X. Carbon Mediated Catalysis: A Review on Oxidative Dehydrogenation. Chin. J. Catal. 2014, 35, 824−841. (4) Su, D. S.; Perathoner, S.; Centi, G. Nanocarbons for the Development of Advanced Catalysts. Chem. Rev. 2013, 113, 5782− 5816. (5) Qi, W.; Su, D. Metal-Free Carbon Catalysts for Oxidative Dehydrogenation Reactions. ACS Catal. 2014, 4, 3212−3218. (6) Frank, B.; Blume, R.; Rinaldi, A.; Trunschke, A.; Schlögl, R. Oxygen Insertion Catalysis by sp2 Carbon. Angew. Chem., Int. Ed. 2011, 50, 10226−10230. (7) Primo, A.; Neatu, F.; Florea, M.; Parvulescu, V.; Garcia, H. Graphenes in the Absence of Metals as Carbocatalysts for Selective Acetylene Hydrogenation and Alkene Hydrogenation. Nat. Commun. 2014, 5, 5291. (8) Zhou, K.; Li, B.; Zhang, Q.; Huang, J.-Q.; Tian, G.-L.; Jia, J.-C.; Zhao, M.-Q.; Luo, G.-H.; Su, D. S.; Wei, F. The Catalytic Pathways of Hydrohalogenation over Metal Free Nitrogen-Doped Carbon Nanotubes. ChemSusChem 2014, 7, 723−728. (9) Li, X.; Pan, X.; Yu, L.; Ren, P.; Wu, X.; Sun, L.; Jiao, F.; Bao, X. Silicon Carbide-Derived Carbon Nanocomposite as a Substitute for Mercury in the Catalytic Hydrochlorination of Acetylene. Nat. Commun. 2014, 5, 3688. (10) Zhu, Y. P.; Guo, C.; Zheng, Y.; Qiao, S.-Z. Surface and Interface Engineering of Noble-Metal-Free Electrocatalysts for Efficient Energy Conversion Processes. Acc. Chem. Res. 2017, 50, 915−923. (11) Drago, R. S.; Jurczyk, K. Oxidative Dehydragenation of Ethylbenzene to Styrene over Carbonaceous Catalysts. Appl. Catal., A 1994, 112, 117−124. (12) Pereira, M. F. R.; Orfao, J. J. M.; Figueiredo, J. L. Oxidative Dehydrogenation of Ethylbenzene on Activated Carbon Catalysts. I. Influence of Surface Chemical Groups. Appl. Catal., A 1999, 184, 153− 160. (13) Mestl, G.; Maksimova, N. I.; Keller, N.; Roddatis, V. V.; Schlögl, R. Carbon Nanofilaments in Heterogeneous Catalysis: an Industrial Application for New Carbon Materials? Angew. Chem., Int. Ed. 2001, 40, 2066−2068. (14) Wang, L.; Zhang, J.; Su, D. S.; Ji, Y.; Cao, X.; Xiao, F.-S. Simple Preparation of Honeycomb-Like Macrostructured and Microporous Carbons with High Performance in Oxidative Dehydrogenation of Ethylbenzene. Chem. Mater. 2007, 19, 2894−2897. (15) Su, D.; Maksimova, N. I.; Mestl, G.; Kuznetsov, V. L.; Keller, V.; Schlögl, R.; Keller, N. Oxidative Dehydrogenation of Ethylbenzene to Styrene over Ultra-Dispersed Diamond and Onion-Like Carbon. Carbon 2007, 45, 2145−2151. (16) Schwartz, V.; Xie, H.; Meyer, H. M., III; Overbury, S. H.; Liang, C. Oxidative Dehydrogenation of Isobutane on Phosphorous-Modified Graphitic Mesoporous Carbon. Carbon 2011, 49, 659−668. (17) Schwartz, V.; Fu, W.; Tsai, Y.-T.; Meyer, H. M., III; Rondinone, A. J.; Chen, J.; Wu, Z.; Overbury, S. H.; Liang, C. OxygenFunctionalized Few-Layer Graphene Sheets as Active Catalysts for Oxidative Dehydrogenation Reactions. ChemSusChem 2013, 6, 840− 846. (18) Dathar, G. K. P.; Tsai, Y.-T.; Gierszal, K.; Xu, Y.; Liang, C.; Rondinone, A. J.; Overbury, S. H.; Schwartz, V. Identifying Active Functionalities on Few-Layered Graphene Catalysts for Oxidative Dehydrogenation of Isobutane. ChemSusChem 2014, 7, 483−491. (19) Zhang, J.; Liu, X.; Blume, R.; Zhang, A.; Schlögl, R.; Su, D. S. Surface-Modified Carbon Nanotubes Catalyze Oxidative Dehydrogenation of n-Butane. Science 2008, 322, 73−77. (20) Primo, A.; Parvulescu, V.; Garcia, H. Graphenes as Metal-Free Catalysts with Engineered Active Sites. J. Phys. Chem. Lett. 2017, 8, 264−278. (21) Navalon, S.; Dhakshinamoorthy, A.; Alvaro, M.; Antonietti, M.; Garcia, H. Active Sites on Graphene-Based Materials as Metal-Free Catalysts. Chem. Soc. Rev. 2017, 46, 4501−4529. (22) Li, B.; Su, D. The Nucleophilicity of the Oxygen Functional Groups on Carbon Materials: a DFT Analysis. Chem. - Eur. J. 2014, 20, 7890−7894.

of the catalytic systems. A proper design and synthesis of model carbon materials and the applications of surface chemistry techniques may be the best way to reveal carbon catalytic reaction mechanism integrally. The in situ characterization and quantification of defects are also important for evaluating the activation of oxygen molecules. Nanocarbon catalysts exhibit potential in industrial alkane dehydrogenation processes, and CNTs with relatively high thermal stability and low cost may be the most preferred forms. Several successful attempts in shaping the nanocarbon materials have already been reported,46 which may be applicable for large-scale catalytic processes. However, the mechanistic studies on nanocarbon materials via in situ techniques are still the foundation for developing a new generation of green nonmetallic catalysis.

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AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected]. ORCID

Wei Qi: 0000-0003-1553-7508 Notes

The authors declare no competing financial interest. Biographies Wei Qi obtained his B.S. and Ph.D. in physical chemistry from Jilin University in 2005 and 2009, respectively. After 3 years of postdoctoral research at UC Berkeley, he joined Institute of Metal Research (IMR), CAS, and was promoted to Professor in 2014. He has received a number of honors, including Excellent Doctoral Thesis of Jilin Province and Members of the Youth Innovation Promotion Association, CAS. His current research interests focus on the reaction kinetics and mechanism for heterogeneous catalytic systems and design and fabrication of novel nanocatalysts, especially in the field of nonmetallic carbon catalysis. Pengqiang Yan received his B. S. degree in University of Science and Technology of China in 2014. Later that year, he joined IMR as a Ph.D. student under the supervision of Prof. Wei Qi and Prof. Dang Sheng Su. His research work concentrates in the mechanistic studies on nanocarbon catalysis. Dang Sheng Su received his Ph.D. from the Technical University of Vienna in 1991, and then he moved to Fritz Haber Institute (FHI) of the Max Planck Society in Berlin on electron microscopy and heterogeneous catalysis until 2011. He is now the Head of the Catalysis and Materials Division of IMR and also the Director of Energy Research Resources Division at Dalian Institute of Chemical Physics, CAS. His research focuses on carbon-catalysis, energy storage, and electron microscopy.

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ACKNOWLEDGMENTS The authors acknowledge the financial support from the NSFC of China (Grants 2161101164, 91645114, 21573256, and 51521091) and the Youth Innovation Promotion Association, CAS.

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REFERENCES

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Oxidative Dehydrogenation on Nanocarbon - American Chemical

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