Hexagonal BN- and BNO-supported Au and Pt nanocatalysts in carbon monoxide oxidation and carbon dioxide hydrogenation reactions

https://doi.org/10.1016/j.apcatb.2021.120891Get rights and content

Highlights

  • Au/h-BN(O) and Pt/h-BN(O) nanohybrids are studied in CO oxidation and CO2 hydrogenation reactions

  • Pt/h-BN(O) exhibits high catalytic activity in CO conversion and CO2 hydrogenation

  • BNO-based catalysts show higher activity compared to their oxygen-free counterparts

  • DFT calculations indicate that Pt-BN interactions affect oxygen and hydrogen molecule absorptions

Abstract

Environmental protection requires solving the problem of utilization and reduction of CO and CO2 emissions. Herein, Au/h-BN(O) and Pt/h-BN(O) nanohybrids are thoroughly analyzed in CO oxidation and CO2 hydrogenation reactions. The nanohybrids differ in catalytic particle size and particle distribution. The particles are smaller (1–6 nm) and display a narrower size distribution in the case of Pt-based nanomaterials. The Pt/h-BN(O) nanohybrids exhibit high catalytic activity in CO conversion and carbon dioxide hydrogenation reactions. For both systems, the oxidative state of BN support affects the catalytic activity. The possible catalytic reaction mechanisms are proposed based on DFT calculations. A charge density distribution at the Pt/h-BN interface increases oxygen absorption, thereby accelerating oxygen-associated chemical reactions.

Introduction

The on-going development of industrial technologies and associated growth in the production and consumption of energy resources have made a significant contribution to improving the quality of life, but this is accompanied with strong environmental pollution by CO and CO2 gases. The most effective ways to utilize and reduce their emissions are CO oxidation and CO2 hydrogenation based on heterogeneous catalysis. Depending on the processing conditions and the nature of catalyst, reduction of CO2 with hydrogen produces either CO, which is a valuable raw material for several chemical syntheses, or CH4. Noble metals are used in many industrial catalytic processes and they are able to dissociate molecular oxygen even at low temperatures and bind strongly to atomic oxygen and CO. These are important characteristics of effective catalysts [1], [2], [3].

Noble metal-based catalysts have shown high efficiency in CO oxidation reaction in the production of high-purity hydrogen for fuel cells via selective oxidation in the process of steam reforming, partial catalytic oxidation, and autothermal reforming of liquid fuels and hydrocarbons [4], [5]. Gold (Au) and platinum (Pt) nanoparticles (NPs) are well known as effective low temperature catalysts. Therefore, the production of dispersed supported noble metal NPs is of great interest for heterogeneous catalysis [6], [7], [8]. Au and Pt catalysts are used in chemical industry for processing hydrocarbons and polymer production [9]. Noble metal NPs-based catalysts have been commercially developed and used in systems for gas purification from CO, including gas masks [10].

The properties of various catalytic systems strongly depend on a support of catalytically active materials [11]. Such support can affect various chemical reactions while accelerating some and slowing down or even stopping the others. The support can change the dispersion of catalytically active NPs and their thermal stability by forming chemical bonds with the active material. This prevents nanoparticle agglomeration and changes the chemical properties of the active material through chemical bonds polarization. In recent years, hexagonal boron nitride (h-BN), which can be obtained in various morphologies with a high specific surface area, has been regarded as a promising support material. It has been shown that defects in h-BN structure (B and N vacancies, as well as N atoms substituted by B atoms) contribute to the dissociation of hydrogen molecules [12]. The chemisorption of CO molecules on h-BN defects can be accompanied by a charge transfer and can lead to narrowing of the band gap [13]. BN surface defects result in the polarization of electron density in the catalytically active particles, thereby improving their functional characteristics [14], [15]. Theoretical investigations indicate that metal atoms interact with h-BN surface defects; this prevents their aggregation [16]. Moreover, metal atoms embedded into h-BN surface effectively activate CO molecules. This leads us to consider that a metal/h-BN system could be a potentially effective catalyst for carbon monoxide oxidation.

Experimental and theoretical studies have also shown that the morphologies of catalyst and support both affect the reactivity of oxygen and the metal-support interactions. This is manifested in the catalyst activity. For example, it has been shown that the shape and size of catalyst NPs and nanostructured features of the support can significantly affect the oxygen activity, which is explained by different types of defects and the presence of isolated or clustered vacancies [17]. It has also been demonstrated that the adsorption of СО2 changes depending on the crystallographic orientation of the catalytically active NPs; this affects the desorption of the final products and conversion of CO [18].

Available data indicates that the usage of h-BN as a support can increase the catalyst activity compared to commonly used supports. Due to their layered structure, h-BN nanosheets enable a high-density attachment of metal NPs leading to an enhanced catalytic activity [19], [20], [21]. As a result of redistribution of electron density, defect-free h-BN surface possesses catalytic activity under interactions with metal NPs [22]. The presence of vacancy defects over h-BN surface can additionally enhance metal-support interaction via electron donor/acceptor mechanisms [23]. This can significantly improve the activity of a catalyst.

Theoretical studies have shown a high efficiency of metal nanoparticle catalysts supported on h-BN nanostructures in CO oxidation process [14], [24]. BN had usually been considered as a chemically inert material until its unusual behavior was discovered during catalysis. Catalytic activity of pure h-BN nanosheets was explained by the presence of oxygen-terminated “armchair” BN edges that act as catalytic active sites [25]. Due to high oxidation resistance of h-BN, it is difficult to form B-O active sites at the “armchair” edges during oxidative dehydrogenation. C-H activation to form B-O(H) active sites has been proposed to explain this mechanism [26].

A study of molecular adsorption energy on the surface of support and catalytically active phase made a great contribution to understanding the catalyst efficiency. The dissociations of small molecules onto graphene, h-BN, BN-doped graphene, and C-doped h-BN using density functional theory (DFT) were studied and a significant difference in dissociative adsorption energies of H2, methane, water, and methanol on the surface of these materials was documented [27]. Doping of pristine h-BN with carbon atoms increases the adsorption energies of molecules, wherein the reactivity toward non-polar adsorbates increases even more significantly.

In this study, Au and Pt NPs on the surface of two types of h-BN nanosheets (reduced and oxidized) were fabricated and thoroughly analyzed as promising catalysts in carbon monooxide oxidation and carbon dioxide hydrogenation reactions. Oxygen activation mechanisms and metal-support interactions are then discussed. The obtained materials are considered as universal catalysts in the CO oxidation and CO2 hydrogenation reactions.

Section snippets

Catalyst support fabrication

BN nanoparticles were produced via plasma-chemical synthesis using boron trichloride ("Plazmotherm", Russia). The nanoparticle size was 20–50 nm. The particles were organized in stacks made of 10–15 atomic BN layers. The specific surface area of BN nanoparticles measured by the BET method was 203 m2/g. The obtained material was purified from the possible secondary phases under annealing at 1500 °C for 2 h in vacuum. This type of BN nanoparticles is denoted as BNNPs. The half of annealed BNNPs

Structural characterization

FTIR spectra of BNNPs (annealed in vacuum at 1500 °C for 2 h) and BNNPsOx (annealed in air at 1100 °C for 2 min) samples are shown in Fig. 1a. The spectra reveal two main features: broad bands in a range of 781–808 cm−1, corresponding to out-of-plane B-N-B bending (R mode), and 1358–1379 cm−1, corresponding to in-plane B-N stretching vibrations (LO mode) [35]. In high-purity crystalline BN, stretching of h-BN network in tangential directions can lead to the appearance of additional adsorption

Discussion

Our experimental and theoretical results indicate that h-BN supported Pt NP catalysts exhibit high catalytic activity in CO oxidation and CO2 hydrogenation reactions. In addition, the oxidative state of BN support affects the catalytic activity. To understand the observed difference in the material catalytic behavior, several factors should be considered: (i) type of catalytically active centers and their adsorption capacities, (ii) nanoparticle size and distribution over the support surface,

Conclusions

Au/h-BN(O) and Pt/h-BN(O) nanohybrids have been fabricated using an impregnation method on plasma-chemical synthesized h-BN supports and analyzed as promising catalysts in carbon monooxide oxidation and carbon dioxide hydrogenation reactions. The important findings are:

  • 1)

    At the same metal loading doze of 4 wt%, nanoparticle dispersion in the Pt- and Au-based catalysts is different. In the Au-based materials, a broad particle size distribution is observed; the particle size is 2–14 nm (Au/h-BN)

CRediT authorship contribution statement

Andrey M. Kovalskii: Conceptualization, Methodology, Investigation, Formal analysis. Ilia N. Volkov: Conceptualization, Investigation, Visualization. Nikolay D. Evdokimenko: Investigation, Visualization. Olga P. Tkachenko: Investigation, Visualization. Denis V. Leybo: Investigation, Visualization. Ilya V. Chepkasov: Methodology, Validation. Zakhar I. Popov: Methodology, Validation. Andrei T. Matveev: Investigation, Visualization. Anton Manakhov: Data curation, Formal analysis. Elizaveta S.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

The authors gratefully acknowledge the financial support from the Russian Science Foundation (Agreement No. 20-79-10286) in the part of catalyst fabrication, characterization, and testing in CO2 hydrogenation reaction and the Ministry of Education and Science of the Russian Federation (Increase Competitiveness Program of NUST "MISiS" No. K2-2020-009) in the part of theoretical calculations. I.N.V. thanks the Russian Foundation for Basic Research (Agreement No. № 20-33-90070\20) in the part of

References (76)

  • Y. Cao et al.

    Defect-induced efficient dry reforming of methane over two-dimensional Ni/h-boron nitride nanosheet catalysts

    Appl. Catal. B Environ.

    (2018)
  • S.-E. Fu et al.

    A first principles study of CO oxidation over gold clusters: The catalytic role of boron nitride support and water

    Mol. Catal.

    (2019)
  • C. Megías-Sayago et al.

    Influence of gold particle size in Au/C catalysts for base-free oxidation of glucose

    Catal. Today

    (2018)
  • K.I. Hadjiivanov et al.

    Characterization of oxide surfaces and zeolites by carbon monoxide as an IR probe molecule

    Adv. Catal.

    (2002)
  • D.V. Shtansky et al.

    Crystallography and structural evolution of cubic boron nitride films during bias sputter deposition

    Acta Mater.

    (2000)
  • D.K. Singh et al.

    Diameter dependence of interwall separation and strain in multiwalled carbonnanotubes probed by X-ray diffraction and Raman scattering studies

    Diam. Relat. Mater.

    (2010)
  • B. Zhong et al.

    Fabrication and Raman scattering behavior of novel turbostratic BN thin films

    Mater. Lett.

    (2015)
  • M. Haruta et al.

    Low-Temperature Oxidation of CO over Gold Supported on TiO2, α-Fe2O3, and Co3O4

    Catal

    (1993)
  • S.-E. Fu et al.

    A first principles study of CO oxidation over gold clusters: The catalytic role of boron nitride support and water

    Mol. Catal.

    (2019)
  • S. Saeidi et al.

    Mechanisms and kinetics of CO2 hydrogenation to value-added products: A detailed review on current status and future trends

    Renew. Sustain. Energy Rev.

    (2017)
  • S. Saeidi et al.

    Hydrogenation of CO2 to value-added products—A review and potential future developments

    J. CO2 Util.

    (2014)
  • X. Chen et al.

    Catalytic performance of the Pt/TiO2 catalysts in reverse water gas shift reaction: Controlled product selectivity and a mechanism study

    Catal. Today

    (2017)
  • M. Schmal

    Heterogeneous catalysis and its industrial applications

    Springer

    (2016)
  • D. Pakhare et al.

    A review of dry (CO2) reforming of methane over noble metal catalysts

    Chem. Soc. Rev.

    (2014)
  • J. Huang et al.

    Heterogeneous catalysis by gold clusters

    Bridg. Heterog. Homog. Catal., John Wiley Sons, Ltd

    (2014)
  • N. Iwasa et al.

    New supported Pd and Pt alloy catalysts for steam reforming and dehydrogenation of methanol

    Top. Catal.

    (2003)
  • X. Wu et al.

    Defects-enhanced dissociation of H2 on boron nitride nanotubes

    J. Chem. Phys.

    (2006)
  • M. Gao et al.

    CO oxidation on h-BN supported Au atom

    J. Chem. Phys.

    (2013)
  • A. Lyalin et al.

    Theoretical predictions for hexagonal BN based nanomaterials as electrocatalysts for the oxygen reduction reaction

    Phys. Chem. Chem. Phys.

    (2013)
  • X. Liu et al.

    Copper atoms embedded in hexagonal boron nitride as potential catalysts for CO oxidation: a first-principles investigation

    RSC Adv.

    (2014)
  • A. Trovarelli et al.

    Ceria catalysts at nanoscale: how do crystal shapes shape catalysis?

    ACS Catal.

    (2017)
  • H. Mistry et al.

    Nanostructured electrocatalysts with tunable activity and selectivity

    Nat. Rev. Mater.

    (2016)
  • A.S. Konopatsky et al.

    Structural evolution of Ag/BN hybrids via a polyol-assisted fabrication process and their catalytic activity in CO oxidation

    Catal. Sci. Technol.

    (2019)
  • A. Lyalin et al.

    Adsorption and catalytic activation of the molecular oxygen on the metal supported h-BN

    Top. Catal.

    (2014)
  • J.T. Grant et al.

    Selective oxidative dehydrogenation of propane to propene using boron nitride catalysts

    Science

    (2016)
  • R. Huang et al.

    Direct insight into ethane oxidative dehydrogenation over boron nitrides

    ChemCatChem

    (2017)
  • Y.S. Al-Hamdani et al.

    Tuning dissociation using isoelectronically doped graphene and hexagonal boron nitride: Water and other small molecules

    J. Chem. Phys.

    (2016)
  • A.A. Davydov

    Molecular Spectroscopy of Oxide Catalyst Surfaces

    Wiley Intersci. Publ.

    (2003)
  • Cited by (28)

    View all citing articles on Scopus
    View full text