REPORT◥

CATALYSIS

Identification of single-site goldcatalysis in acetylene hydrochlorinationGrazia Malta,1 Simon A. Kondrat,1 Simon J. Freakley,1 Catherine J. Davies,1 Li Lu,2

Simon Dawson,1 Adam Thetford,3,4 Emma K. Gibson,3,4 David J. Morgan,1 Wilm Jones,3

Peter P. Wells,3,4,5 Peter Johnston,6 C. Richard A. Catlow,1,3,4

Christopher J. Kiely,2 Graham J. Hutchings1*

There remains considerable debate over the active form of gold under operatingconditions of a recently validated gold catalyst for acetylene hydrochlorination. Wehave performed an in situ x-ray absorption fine structure study of gold/carbon (Au/C)catalysts under acetylene hydrochlorination reaction conditions and show that highlyactive catalysts comprise single-site cationic Au entities whose activity correlateswith the ratio of Au(I):Au(III) present. We demonstrate that these Au/C catalystsare supported analogs of single-site homogeneous Au catalysts and propose amechanism, supported by computational modeling, based on a redox couple ofAu(I)-Au(III) species.

Amajor environmental landmark occurredin late 2015 with the commercialization ofcarbon-supported gold as a catalyst for acet-ylene hydrochlorination in China (1, 2).Since the 1950s, mercuric chloride sup-

ported on carbon has been used as a catalyst forthe production of vinyl chloride monomer (VCM)via this reaction. In 1985, Hutchings predicted(3) that gold should be the best catalyst for thisreaction and subsequently showed this to be thecase by experiment (4). During the past decade,the manufacture of VCM has increased markedlyin China, partly because of the availability of coalas a feedstock for acetylene production. However,

this trend has increased the environmental burdenresulting from mercury pollution and, with thesigning of the Minamata accord (5), a replacementfor mercuric chloride in the acetylene hydrochlorin-ation reaction was mandated. The use of carbon-supported gold for this reaction represents thefirst time in more than 50 years that there hasbeen a total change in the catalyst composition forthe manufacture of a major commodity chemical.The key question that remains is What is the

nature of the active gold species under acetylenehydrochlorination reaction conditions? Ex situspectroscopy and electronmicroscopy (6–9) studieshave suggested that gold nanoparticles are present

and the active sites are cationic gold associatedwith these nanoparticles (6, 10). Recently, a pos-sible role for Au(I) as well as Au(III) has beenimplicated in acetylene hydrochlorination (11)and other reactions (12, 13). Since the originaldisclosure of gold as an effective catalyst for al-kyne transformations (14), numerous examplesof Au(I) complexes have been described for suchreactions, which suggests that the active goldcatalyst for acetylene hydrochlorination couldbe a supported gold cation. Single gold cationshave been implicated in heterogeneous catalystsbefore (15–18), but these materials either deactivaterapidly or form substantial concentrations of goldclusters or nanoparticles after reaction. We havenow performed in situ x-ray absorption fine struc-ture (XAFS) experiments to definitively show thatthe active catalyst for acetylene hydrochlorinationpredominantly comprises Au(I) isolated cationicspecies analogous with the single-site homogeneouscatalysis afforded by Au(I) complexes (19, 20). Foran in situ XAFS study of these homogeneous gold-catalyzed reactions, see (21).A series of 1 weight % (wt %) Au materials

supported on carbon powder were prepared byimpregnation with HAuCl4 dissolved in eitheraqua regia, HNO3, or H2O by previously describedmethods (designated as Au/C-AR, Au/C-HNO3,and Au/C-H2O, respectively) (11). Scanning trans-mission electron microscopy (STEM) analysis of

RESEARCH

Malta et al., Science 355, 1399–1403 (2017) 31 March 2017 1 of 4

1Cardiff Catalysis Institute, School of Chemistry, CardiffUniversity, Main Building, Park Place, Cardiff CF10 3AT, UK.2Department of Materials Science and Engineering, LehighUniversity, 5 East Packer Avenue, Bethlehem, PA 18015, USA.3UK Catalysis Hub, Research Complex at Harwell, RutherfordAppleton Laboratory (RAL), Oxford OX11 0FA, UK. 4KathleenLonsdale Building, Department of Chemistry, University CollegeLondon, Gordon Street, London WC1H 0AJ, UK. 5School ofChemistry, University of Southampton, Southampton SO17 1BJ,UK. 6Diamond Light Source, Harwell Science and InnovationCampus, Chilton, Didcot OX11 0DE, UK. 7Process Technologies,Johnson Matthey PLC, Billingham TS23 1LB, UK.*Corresponding author. Email: hutch@cf.ac.uk

Fig. 1. Characterization of a freshly prepared 1 wt% Au/C-AR catalyst. (A) RepresentativeSTEM-HAADF image showing isolated Au species. (B) Powder x-ray diffraction data for thiscatalyst. (C) Fourier transform of k3-weighted c EXAFS ex situ data of the sample and a gold-foil reference. Variation in magnitude of Fourier transform is plotted with distance R from theAu absorber. (D) Ex situ Au L3 edge–normalized XANES spectra of the sample and a gold-foilreference material.

on June 16, 2020

http://science.sciencemag.org/

Dow

nloaded from

the Au/C-AR catalyst (Fig. 1A) revealed the pres-ence of predominantly highly dispersed isolatedAu species. Some dimeric Au species were alsoidentified, although they were a relatively minorcomponent compared to the isolated monomericAu species (fig. S3) (22). This finding was sup-ported by x-ray diffraction (XRD) (Fig. 1B), whereno reflections associated with metallic Au nano-particles were observed. The lack of long-rangeorder was further corroborated by extended x-rayabsorption fine structure (EXAFS) analysis (Fig. 1C),where no Au-Au characteristic distances weredetected. In addition, substantial contributionsfrom Au-Cl entities can be seen in the EXAFSFourier transform (FT). Fitting a first coordina-tion shell for Au-Cl gave an average coordinationnumber (CN) of 2.6 (table S1). Furthermore, ex situCl K-edge x-ray absorption near-edge structure(XANES) studies confirmed the presence of Au-Clbonding (fig. S4).Further information on Au speciation can be

determined from the normalized Au L3-edgeXANES (see supplementary materials for experi-mental details). The white-line intensity (a strongadsorption feature associated with Au 2p3/2 core–electron excitation to unoccupied 5d or 6s states)is indicative of 5d-band occupancy; Au specieswith higher oxidation states (i.e., reduced 5d elec-tron occupancy) have stronger white-line adsorp-tion features. Analysis of the white-line intensityduring XANES measurements, when comparedto appropriate standards, has precedence in theliterature as a reliable method of identifying Auoxidation state (23, 24), The typical normalizedwhite-line intensity values observed for cationicAu standards of Au(III) (e.g., KAuCl4/[AuCl4]

–)and Au(I) (e.g., [AuCl2]

–) are 1.1 and 0.6, respec-tively, and correlate well with measured valuesfrom our chosen standard materials (fig. S5)(23, 25). The white-line intensity (Fig. 1D) of thefresh Au/C-AR catalyst was 0.78, indicating asubstantially oxidized Au speciation, with linearcombination fitting showing no contribution fromAu(0) (within fitting error), 56% from [AuCl2]

–, and44% from [AuCl4]

– (table S2). Notably, we havenot relied upon x-ray photoelectron spectroscopy(XPS) for characterization because of observable

beam-induced photoreaction of Au(III) salts (fig.S6), which will overstate Au(0) content in the Au/C catalysts. Photoreduction did not occur withsynchrotron radiation in the XAFS techniquebecause of the higher photon incident energy,which results in a notably lower absorption crosssection compared with XPS (fig. S6).The Au/C-AR catalyst has an induction period

typically of 1 hour, strongly suggesting that itsactive form is generated under reaction conditions(11). To investigate the nature of the Au speciesunder in situ acetylene hydrochlorination reac-tion conditions, we used a purpose-built micro-reactor to perform XAFS analysis while followingthe reaction by mass spectrometry (see supple-mentary materials for experimental details). Underthe dilute reaction conditions (2.36% C2H2 and2.40% HCl) that we needed with this apparatus,we observed increasing acetylene conversionwith increasing time-on-line (time that the reac-tion is ongoing). However, the induction periodoccurred over a longer time span (3 hours) underthese dilute conditions (Fig. 2A). All of the Au/Ccatalysts we tested were highly selective towardVCM; no dichloroethene or chloroethane productswere detected at any level of acetylene conversion.We used in situ XAFS to monitor changes in

Au speciation of the Au/C-AR catalyst upon heat-ing to reaction temperature (200°C) under aninert atmosphere, before the addition of reactants.On heating, a decrease in white-line intensityfrom 0.78 at 25°C to 0.68 was observed, whichsuggests a change from a mixed Au(III)/Au(I)chloride speciation to a Au(I) chloride-like species.This change correlates well with the decompo-sition temperature of AuCl3 to AuCl that oc-curs at ~160°C (26). The white-line intensitywas stable at 0.68 during the 30 min isothermat 200°C, before the addition of reactant gases(fig. S7). The continued absence of any detect-able Au-Au distances in the catalyst indicatesthat the Au remained in a highly dispersed state.Further analysis of the Au/C-AR catalyst showed

that upon introduction of the reactant gasesan immediate change in the Au L3-edge XANESspectrum occurred (Fig. 2, A and B). The white-line intensity increased from 0.68 to 0.94 during

the first 20 min time-on-line and then steadilydecreased back to a stable value of 0.72 after~180 min. This observation suggests that Au(I)chloride-like species initially present were oxi-dized to predominantly Au(III) chloride speciesby the reactants during the first 20 min, andduring the subsequent 160 min of reaction, theaverage oxidation state of the Au species grad-ually moved back toward that of Au(I) beforeconverging to a stable condition somewhere be-tween the two extremes. After the initial 15-mintime-on-line, where reaction conditions reachedsteady state, the measured change in relativewhite-line intensity correlated strongly with thesimultaneously recorded VCM productivity of thecatalyst (Pearson correlation coefficient value r of–0.995 as shown in fig. S8), with higher pro-ductivity being observed with lower Au white-line relative intensity. Notably, no characteristicAu-Au distances were measurable by EXAFSwhile the catalyst was producing VCM duringthe entire reaction period (fig. S9A). Linear com-bination fitting analysis of XANES spectral datawith [AuCl4]

–, [AuCl2]–, and Au-foil standard

spectra showed a trend similar to that deducedfrom the white-line intensity analysis (fig. S10A).However, poor R-factor fitting values in the linearcombination fitting (fig. S11) imply that our inter-pretation of the XANES spectral changes beingsolely associated with variations in the relativeconcentrations of [AuCl4]

– and [AuCl2]– could

be an oversimplification. XANES spectra are in-fluenced by the hybridization of substrate mole-cule and metal d-band orbitals (27, 28) and bychanges in metal-speciation geometry throughinteraction with the support (29). Both of thesereported complications are conceivable in thiswork, in the form of (i) interactions betweenthe acetylene p and Au (5d) orbitals and (ii) C-AuClx geometric effects. However, we observeda linear correlation between white-line intensityand the EXAFS-derived Au-Cl CN at a range ofreaction times (fig. S12), which supports our in-terpretation of the white-line intensity as beingdirectly associated with changes in the Au-Clspeciation. Analysis of the spent catalyst by STEM–high-angle annular dark-field (HAADF) imaging

Malta et al., Science 355, 1399–1403 (2017) 31 March 2017 2 of 4

Fig. 2. VCM productivity and in situ characterization of 1 wt % Au/C-AR catalyst as a function of time-on-line. (A) Catalytic performance as afunction of time-on-line (black) and the change in normalized white-line intensity (blue) as a function of reaction time. (B) Three-dimensional profile plotof successive Au L3 edges from XANES spectra acquired in situ as a function of reaction time. (C) Representative STEM-HAADF image of Au/C-AR afteruse for 240 min showing the presence of atomically dispersed species and a few occasional subnanometer clusters.

RESEARCH | REPORTon June 16, 2020

http://science.sciencemag.org/

Dow

nloaded from

confirmed the prevalence of atomically dispersedAu species as well as some occasional subnano-meter clusters, but there was a total absence ofany metallic Au nanoparticles (Fig. 2C).To further reinforce our findings, we per-

formed comparable in situ XAFS studies, alongwith reaction effluent analysis, on correspondingAu/C catalysts prepared with nitric acid or water.The Au/C-HNO3 catalyst was reported to havesome activity and display an induction period com-parable to that of the Au/C-AR catalyst (11), whichwas also extended by the dilute reaction condi-tions. Ex situ characterization of the Au/C-HNO3

sample showed lower Au dispersion when com-pared to Au/C-AR, with some evidence of metallicAu particles from XRD (fig. S13). However, in situEXAFS and XANES of Au/C-HNO3 under reactionconditions showed that the active stable cata-lyst was still predominantly composed of cat-ionic AuClx species (figs. S9B and S10B). Thesame correlation between Au L3-edge white-lineintensity and catalytic activity as found for Au/C-AR materials was observed (Fig. 3A). In con-trast the catalytic activity of the Au/C-H2O mate-rial, as when measured under more concentratedreaction mixtures (11), was very low and showedno improvement with reaction time-on-line.This catalyst was composed predominantly ofmetallic-Au nanoparticles (as observed fromXRD, fig. S13; and STEM, fig. S14), and no whiteline was observed in XANES (Fig. 3A), indicat-

ing very low concentrations of dispersed Auspecies. Indeed, this catalyst was the only onewe investigated that had discernible Au-Au scat-tering paths in the FT of the EXAFS data andshowed no characteristic Au-Cl distances (Fig. 3B).Under reaction conditions, almost no changewas observed in the in situ XANES or EXAFSspectra (fig. S9C and S10C).We also prepared a Au/C catalyst by using

Au(I)-thiosulfate as a precursor complex (des-ignated Au/C-S2O3) that was a more stable andactive catalyst under reaction conditions thanthose made with the HAuCl4 precursor. Wehave demonstrated that use of a more stablecationic gold complex prepared from a range ofsulfur-containing ligands, such as thiosulfate,results in highly active catalysts at low goldloadings (1, 30). The catalytic activity of Au/C-S2O3 was similar to that of the steady-stateactivity of the Au/C-AR catalyst (Fig. 3A), but ithad no induction period. As with the Au/C-ARand Au/C-HNO3 materials, EXAFS analysis ofthe fresh Au/C-S2O3 sample showed no Au-Audistances and a substantial contribution froma Au scattering path with a low–atomic numberneighbor (Fig. 3B). Given the similar nature ofCl and S from an EXAFS perspective and Au-thiosulphate complexes having two Au–S bondswith an angle near 180° (31) (almost identical tothe molecular geometry of [AuCl2]

–), we cannotdistinguish between Au-Cl and Au-S scattering

paths by EXAFS. A fitting of the EXAFS data fromthe fresh Au/C-S2O3 catalysts (table S1) gave a CNof 2.0 (±0.1), showing that the Au-bonded specieswas the Au-thiosulfate complex. This CN corre-sponded well with the white-line intensity of 0.68,further showing that the catalyst comprised pre-dominantly Au(I) species before reaction (Fig.3A). Upon the addition of the reactant gases, aslight increase in white-line intensity to 0.78(with concomitant Au-S and/or Au-Cl CN of 2.6)was observed after 30 min, indicating oxida-tion of some of the Au species to Au(III) (Fig.3A). This increase in CN above the initial valueof 2.0 shows that Cl is coordinated to the Au-thiosulphate complex. Notably, the increase inwhite-line intensity was far less than that withthe Au/C-AR catalyst, which is consistent withthe lack of induction period for the Au/C-S2O3

catalysts. As with Au/C-ARmaterials, both EXAFSand STEM-HAADF imaging studies (figs. S9Dand S15) of the Au/C-S2O3 catalysts showed thatthe Au was almost entirely in an atomically dis-persed form (with only a few dimeric species)on the C support both before and after the insitu experiments. Notably, the relative white-lineintensity of the Au/C-S2O3 catalyst at steady statewas the same as for the Au/C-AR catalyst at sim-ilar activity.Figure 3C shows that a correlation can be

made between the white-line intensity and VCMproduction of the three active catalysts (Au/C-AR,

Malta et al., Science 355, 1399–1403 (2017) 31 March 2017 3 of 4

Fig. 3. VCM productivity (first 90 min time-on-line)and in situ XAFS characterization of alternativelyprepared 1 wt % Au/C catalysts. (A) Catalytic activity(black line) as a function of time-on-line for the catalystsprepared with nitric acid, thiosulphate, and water. Theblue lines show the corresponding change in relativewhite-line intensity as a function of reaction time. (B) k3-weighted c EXAFS Fourier transform data for 1 wt %Au/C-HNO3 (black), 1 wt % Au/C-S2O3 (blue), 1 wt %Au/C-H2O (green), and reference gold foil (red). (C) Dashedlines represent the white-line intensities of the Au(I) [AuCl2]

–

standard (value of 0.6) and the Au(III) KAuCl4 standard(value of 1.1). [AuCl2]

– standard from difference spectracalculated in (23).

RESEARCH | REPORTon June 16, 2020

http://science.sciencemag.org/

Dow

nloaded from

Au/C-HNO3, and Au/C-S2O3) throughout theirinduction periods and at steady state; this cor-relation suggests that the highly dispersed Au(I)species are crucially important for this reac-tion and that similar oxidation-state speciesare responsible for the activity in these catalystsystems. However, in all catalysts that are highlyactive, there is also a population of highly dis-persed Au(III)-like species present, which couldsuggest, as originally predicted based on corre-lations with standard electrode potential (3),that the activity is related to a Au(I)-Au(III) re-dox couple. Mechanistically, the reaction couldbe hypothesized to proceed through the oxida-tive addition of HCl to Au chloride, followed bythe addition of acetylene and reductive elim-ination of VCM through a Au(I)-Au(III) redoxcouple. This mechanism has generally been dis-regarded, as it requires Au(I) as opposed tothe more frequently observed Au(III) (32). How-ever, under steady-state conditions, the Au(I)/Au(III) ratio is ~1.5, and that activity can be cor-related to the presence of Au(I), as observed inseveral homogeneous systems (33, 34).To investigate the role of Au(I) further, we

have also undertaken a density functional theory(DFT) study of the interaction of HCl with sup-ported Au species (Fig. 4). Here we focus on Au(I),by investigating AuCl on a graphite surface cutin the (119) index plane and hydroxylated onthe step edge to stabilize the edge, which isdescribed in detail in the supplementary ma-terial. HCl is added across the AuCl to formAuCl2H with a barrier of 98 kJ mol−1. This spe-cies shows a higher Hirshfeld charge of 0.37ecompared to 0.19e for the AuCl. The former valueis similar to that for Au(III), which has a charge

of 0.41e when modeled as AuCl3, indicating thatthis species has a more Au(III) character. Themost stable configuration for a HCl moleculeinteracting with AuCl has a binding energy of–131 kJ mol−1, which compares with –73 kJ mol−1

for AuCl2H. Dissociation of the HCl is inhibitedby hydrogen-bonding interactions; moreover,this site can be easily blocked by additional HCl,and other paths for dissociation are less favor-able, as HCl has a lower adsorption energy of–52 kJ mol−1. The generation of VCM can oc-cur via AuCl2(C2H3), which has an increasedstability compared to AuCl2H(C2H2) with a bind-ing energy of –224 kJ mol−1 versus–128 kJ mol−1.VCM is further stabilized with a binding energyof –269 kJ mol−1, but this can be displaced byHCl. The theoretical mechanism, combined withthe observation that under in situ conditions theactive site is a support gold cation, with a cat-alytic cycle involving Au(I) and Au(III), confirmsthe original prediction concerning gold being thebest catalyst for this reaction based on its stan-dard electrode potential (3).

REFERENCES AND NOTES

1. P. Johnston, N. Carthey, G. J. Hutchings, J. Am. Chem. Soc.137, 14548–14557 (2015).

2. R. Ciriminna, E. Falletta, C. Della Pina, J. H. Teles,M. Pagliaro, Angew. Chem. Int. Ed. Engl. 55, 14210–14217(2016).

3. G. J. Hutchings, J. Catal. 96, 292–295 (1985).4. B. Nkosi, N. J. Coville, G. J. Hutchings, Appl. Catal. 43, 33–39

(1988).5. United Nations Environment Programme, Minamata

Convention on Mercury, www.mercuryconvention.org/.6. B. Nkosi et al., J. Catal. 128, 366–377 (1991).7. G. Hong et al., RSC Advances 6, 3806–3814 (2016).8. M. Zhu et al., ACS Catal. 5, 5306–5316 (2015).9. X. Tian et al., RSC Advances 5, 46366–46371

(2015).

10. B. Nkosi, M. D. Adams, N. J. Coville, G. J. Hutchings,J. Catal. 128, 378–386 (1991).

11. X. Liu et al., Catal. Sci. Technol. 6, 5144–5153(2016).

12. S. Carrettin, M. C. Blanco, A. Corma, A. S. K. Hashmi,Adv. Synth. Catal. 348, 1283–1288 (2006).

13. L. Huang, M. Rudolph, F. Rominger, A. S. K. Hashmi,Angew. Chem. Int. Ed. Engl. 55, 4808–4813 (2016).

14. A. S. K. Hashmi, Gold Bull. 36, 3–9 (2003).15. M. Flytzani-Stephanopoulos, Acc. Chem. Res. 47, 783–792

(2014).16. W. Deng, A. I. Frenkel, R. Si, M. Flytzani-Stephanopoulos,

J. Phys. Chem. C 112, 12834–12840 (2008).17. J. C. Fierro-Gonzalez, B. C. Gates, J. Phys. Chem. B 108,

16999–17002 (2004).18. J. Lu, C. Aydin, N. D. Browning, B. C. Gates, Angew. Chem. Int.

Ed. Engl. 51, 5842–5846 (2012).19. M. C. Blanco Jaimes, C. R. N. Böhling, J. M. Serrano-Becerra,

A. S. K. Hashmi, Angew. Chem. Int. Ed. Engl. 52, 7963–7966(2013).

20. M. C. Blanco Jaimes et al., Chem. Commun. (Camb.) 50,4937–4940 (2014).

21. A. S. K. Hashmi et al., Chemistry 16, 8012–8019 (2010).22. See supplementary materials.23. S.-Y. Chang et al., RSC Advances 5, 6912–6918 (2015).24. A. Pantelouris, G. Kueper, J. Hormes, C. Feldmann,

M. Jansen, J. Am. Chem. Soc. 117, 11749–11753 (1995).25. I. Berrodier et al., Geochim. Cosmochim. Acta 68, 3019–3042

(2004).26. O. Glemser, H. Sauer, in Handbook of Preparative Inorganic

Chemistry, G. Brauer, Ed. (Academic Press, ed. 2, 1965), vol. 2,p. 1056.

27. P. Hu, P. N. Duchesne, Y. Song, P. Zhang, S. Chen, Langmuir31, 522–528 (2015).

28. N. Weiher et al., J. Am. Chem. Soc. 129, 2240–2241(2007).

29. M. Fernández-García, Catal. Rev., Sci. Eng. 44, 59–121(2002).

30. P. T. Bishop, N. A. Carthey, P. Johnston, U.S. Patent WO2013008004 A3 (2013).

31. R. A. Bryce, J. M. Charnock, R. A. D. Pattrick, A. R. Lennie,J. Phys. Chem. A 107, 2516–2523 (2003).

32. M. Conte et al., J. Catal. 250, 231–239 (2007).33. M. Pernpointner, A. S. K. Hashmi, J. Chem. Theory Comput. 5,

2717–2725 (2009).34. A. S. K. Hashmi, Angew. Chem. Int. Ed. Engl. 51, 12935–12936

(2012).

ACKNOWLEDGMENTS

We acknowledge Cardiff University for support as partof the MAXNET Energy Consortium. We also thank R. Schlöglfor helpful discussions. UK Catalysis Hub is thanked forresources and support provided through our membershipof the UK Catalysis Hub Consortium and funded by theEngineering and Physical Sciences Research Council(EPSRC) (grants EP/K014706/1, EP/K014668/1, EP/K014854/1EP/K014714/1, and EP/M013219/1). We used the B18 beamlineat the Diamond Light Source (allocation numbers SP10306,SP11398, and SP15214) with the help of D. Gianolio and G. Cibin.C.J.K. acknowledges funding from the National ScienceFoundation Major Research Instrumentation program(GR no. MRI/DMR-1040229). We thank Johnson Matthey fortheir contribution to and funding of this work. Calculationswere performed through our membership of the UK’sHigh-End Computing (HEC) Materials Chemistry Consortium,which is funded by EPSRC (EP/L000202); this work used theAdvanced Research Computing High-End Resource (ARCHER)UK National Supercomputing Service (www.archer.ac.uk).Local high performance computing (HPC) services at UniversityCollege London (UCL) were used on the Grace computer. Wethank S. Morris, A. Davies, and L. Wescombe for technicalsupport. All the data contained in this paper are archivedat doi:10.17035/d.2017.0032403846.

SUPPLEMENTARY MATERIALS

www.sciencemag.org/content/355/6332/1399/suppl/DC1Materials and MethodsFigs. S1 to S15Tables S1 and S2References (35–47)

4 November 2016; accepted 7 March 201710.1126/science.aal3439

Malta et al., Science 355, 1399–1403 (2017) 31 March 2017 4 of 4

Fig. 4. Mechanism for the transformation of AuCl to AuCl2H and formation of VCM reproducingAuCl. Au atoms (gold), Cl atoms (green), H atoms (white), C atoms (gray), and O atoms (red). Thebar chart shows binding energies for each energy minima and the Hirshfeld charge on each Au atom.Energies are given with reference to the geometry-optimized configuration of AuCl on the carbon supportand gas phase acetylene and HCl.

RESEARCH | REPORTon June 16, 2020

http://science.sciencemag.org/

Dow

nloaded from

Identification of single-site gold catalysis in acetylene hydrochlorination

J. HutchingsGibson, David J. Morgan, Wilm Jones, Peter P. Wells, Peter Johnston, C. Richard A. Catlow, Christopher J. Kiely and Graham Grazia Malta, Simon A. Kondrat, Simon J. Freakley, Catherine J. Davies, Li Lu, Simon Dawson, Adam Thetford, Emma K.

DOI: 10.1126/science.aal3439 (6332), 1399-1403.355Science 

, this issue p. 1399Sciencesingle metal atoms that react via a similar redox couple.

cations. These species are analogs of soluble catalysts with3+ and Au+the active species are coexisting single-site Au used x-ray spectroscopic studies of the working catalysts and computational modeling to show thatet al.chloride. Malta

feedstock. However, a more environmentally friendly catalyst of gold supported on carbon can now replace mercuric The mercuric chloride catalyst for acetylene hydrochlorination creates vinyl chloride, an important polymer

Supported gold ions

ARTICLE TOOLS http://science.sciencemag.org/content/355/6332/1399

MATERIALSSUPPLEMENTARY http://science.sciencemag.org/content/suppl/2017/03/29/355.6332.1399.DC1

REFERENCES

http://science.sciencemag.org/content/355/6332/1399#BIBLThis article cites 42 articles, 0 of which you can access for free

PERMISSIONS http://www.sciencemag.org/help/reprints-and-permissions

Terms of ServiceUse of this article is subject to the

is a registered trademark of AAAS.ScienceScience, 1200 New York Avenue NW, Washington, DC 20005. The title (print ISSN 0036-8075; online ISSN 1095-9203) is published by the American Association for the Advancement ofScience

Copyright © 2017, American Association for the Advancement of Science

on June 16, 2020

http://science.sciencemag.org/

Dow

nloaded from