Grafting of a Molecular Rhenium CO2 Reduction Catalyst onto Colloid

Letter www.acsaem.org

Cite This: ACS Appl. Energy Mater. XXXX, XXX, XXX−XXX

Grafting of a Molecular Rhenium CO2 Reduction Catalyst onto Colloid-Imprinted Carbon Janina Willkomm,* Erwan Bertin, Marwa Atwa, Jian-Bin Lin, Viola Birss,* and Warren E. Piers* Department of Chemistry, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada

Downloaded via 146.185.201.224 on April 16, 2019 at 08:45:19 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

S Supporting Information *

ABSTRACT: An aminophenethyl-substituted [Re(2,2′bipyridine)(CO)3Cl] catalyst ([Re(NH2-bpy)]) was tethered to nanoporous colloid-imprinted carbon (CIC) electrode surfaces via an electrochemical oxidative grafting method. Hybrid CIC|[Re(NH2-bpy)] electrodes showed an improved stability and an increased loading per geometrical area in comparison to modified smooth glassy carbon electrodes. The catalyst also remained active upon immobilization, and CO2 was selectively reduced to CO by the CIC|[Re(NH2-bpy)] electrodes in acetonitrile with a Faradaic efficiency of 92 ± 6% and a Re-based TON of approximately 900. KEYWORDS: CO2 reduction, electrocatalysis, rhenium bipyridine, nanoporous carbon, surface anchoring

T

applied in the context of CO2 reduction with molecular catalysts. The large surface area provided by the CIC particles should enable a higher loading of molecular catalyst per geometrical electrode area to be obtained in comparison to the smooth glassy carbon surface, and the large, uniform pores in CIC would allow for good mass transport of CO2 and resulting products within the porous structure.22 The complex [Re(NH2-bpy)] was synthesized from commercially available starting materials in three steps (Scheme S1, see SI for experimental details and characterization). Reacting 4-nitrobenzyl bromide with deprotonated 4,4′-dimethyl-2,2′-bipyridine, followed by reduction of the nitro moiety, afforded the aminophenethyl-substituted bipyridine ligand (NH2-bpy). [Re(NH2-bpy)] was then obtained by heating NH2-bpy with Re(CO)5Cl in toluene, and the complex was characterized by elemental analysis, high-resolution mass spectrometry, 1H and 13C NMR, as well as IR spectroscopy. Single crystal X-ray diffractometry revealed the presence of both possible isomers in the solid-state with octahedral coordination of Re and a typical facial arrangement of the three carbonyl ligands (Figure 1, Table S1), as also evident by IR spectroscopy (see SI). Electrochemical responses of [Re(NH2-bpy)] were recorded in dry ACN under argon using tetrabutylammonium hexafluorophosphate (TBAPF6, 0.1 M) as the supporting electrolyte and a glassy carbon disk as the working electrode. The cyclic voltamogramm (CV) featured a reversible oneelectron and then a quasi-irreversible one-electron reduction reaction at Ep = −1.87 and −2.13 V vs Fc+/Fc, which have

he electrochemical conversion of carbon dioxide (CO2), especially when driven by electricity from renewable sources, is considered a viable route to sustainably produce fuels or chemical feedstocks, such as methanol, methane, or carbon monoxide (CO).1 The complex [Re(2,2′-bipyridine)(CO)3Cl] and its derivatives are a well-explored type of molecular catalyst operating with high efficiency for the selective reduction of CO2 to CO.2−4 Recent advances in this field include their integration with solid-state supports to prepare hybrid CO2-reducing electrodes or materials.5−9 Moving from homogeneous to heterogenized systems has added benefits, such as simplifying recyclability and product separation, as well as directing product selectivity.10 In addition, the confinement on high-surface-area supports has also often led to an improvement of catalyst stability.6,11−15 In general, complexes can be immobilized either via noncovalent interactions,7,9,10 or by forming a covalent bond between the (premodified) surface of a material and a peripheral functional group on the ligand framework.6,16,17 Grafting via the electrochemical oxidation of an amino moiety has been commonly used for anchoring of small molecules to carbon materials by the formation of a C−N bond.18 This method has recently been applied to bind a Re and Mn bipyridine complex to glassy carbon; however, this approach only yielded low catalyst loadings and unstable hybrid electrodes.19 Herein, we report the synthesis of the complex [Re(4-(4aminophenethyl)-4′-methyl-2,2′-bipyridine)(CO)3Cl] ([Re(NH2-bpy)]) and its covalent tethering to colloid-imprinted carbon (CIC) electrodes via the oxidation of its amino group. CIC is a type of nanoporous carbon featuring a high surface area and uniform pores that are tunable in size,20 and they have been studied as electrode or support materials in fuel cells.21,22 To the best of our knowledge, CIC materials have not been © XXXX American Chemical Society

Received: January 30, 2019 Accepted: April 8, 2019 Published: April 9, 2019 A

DOI: 10.1021/acsaem.9b00216 ACS Appl. Energy Mater. XXXX, XXX, XXX−XXX

Letter

ACS Applied Energy Materials

g−1 and an average spherical pore diameter of d = 71 nm.29 Briefly, CIC electrodes were prepared by drop-casting an ink containing CIC particles and Nafion as a binder in ethanol onto a glassy carbon disk (see SI for further experimental details on CIC particles and electrode preparation). To graft the complex to the carbon surface, multiple CVs of the complex were recorded in ACN/TBAPF6 (0.1 M) in the presence of the base 2,4,6-collidine (see SI for further details). A decrease of the irreversible amine oxidation wave at approximately +0.7 V vs Fc+/Fc was indicative of bond formation between the amino group and the surface of the carbon working electrodes (Figures S4 and S5).30 After 20 scans, the electrodes were rinsed with ACN and dried under an argon atmosphere. Multiple CVs of the [Re(NH2-bpy)]modified electrode were subsequently recorded in a fresh electrolyte solution (ACN/0.1 M TBAPF6, no Re complex in solution) by scanning across the bpy/bpy•− and ReI/Re0 redox couples to assess the surface coverage and stability under reducing conditions (Figure 2A and Figure S4). For the glassy carbon disk electrode, an initial loading of 2.9 × 10−11 mol of [Re(NH2-bpy)] or Γ[Re] = 0.42 nmol cm−2 (referenced to the geometrical area of electrode, A = 0.07 cm2) was estimated via integration of the broad redox wave between −1.75 and −2.3 V vs Fc+/Fc (Figure S4, second scan). This

Figure 1. Molecular structure of [Re(NH2-bpy)] with 50% probability ellipsoids. Hydrogen atoms and solvents molecules (acetonitrile, ACN) were omitted for clarity. Selected distances in Å: Re1−Cl1 = 2.484(3); Re1−N1 = 2.168(8); Re1−N2 = 2.168(8); Re2−Cl2 = 2.459(3); Re2−N4 = 2.171(8); Re2−N5 = 2.168(8); Re−C = 1.91−1.99.

been previously assigned to ligand- and metal-based reduction processes, respectively (Figure S1).2 These values closely resemble those obtained for the unmodified parent complex [Re(4,4′-dimethyl-2,2′-bipyridine)(CO)3Cl] ([Re(dmbpy)]) (Table S2),2 which would be expected due to the minimal impact of the additional aminobenzyl group on the electronic properties of the bipyridine ligand. A scan-rate dependent analysis for the first reduction event further confirmed a diffusion-controlled redox process (Figure S1).23 In a CO2-saturated solution, a catalytic reduction wave was observed at a half-wave potential Ecat/2 = −2.09 V vs Fc+/Fc (Figure S1; with Ecat/2 defined as the potential where half the catalytic peak current, i.e., icat, is reached under CO2).24 The ratio between the peak current under catalytic (icat) and inert conditions (ipc; cathodic current of first reduction wave under argon) allowed for an initial assessment of catalytic activity. An icat/ipc ratio of 6.3 was obtained for [Re(NH2-bpy)] vs 10.7 for [Re(dmbpy)] under the same experimental conditions, indicating a somewhat lower CO2 reduction activity for the amino-substituted complex (Table S2). When increasing the scan rate until a plateau was reached for icat under CO2 atmosphere (i.e., achieving “pure kinetic conditions”), the rate constant, kcat, could be determined from the icat/ipc ratio (see SI for equation).25 Rate constants of kcat = 3910 s−1 (at 15 V s−1) and 6430 s−1 (at 20 V s−1) were calculated for [Re(NH2-bpy)] and [Re(dmbpy)], respectively (Figure S2), which are in agreement with the initial assessment via the icat/ ipc ratio. Using the correlation kcat = TOFmax,26 a Tafel plot was constructed to benchmark [Re(NH2-bpy)], showing that its performance is well within the range of previously reported [Re(bpy)] catalysts (Figure S3).2 Finally, controlled potential electrolysis (CPE) experiments with [Re(NH2-bpy)] in ACN/ TBAPF6 (0.1 M) at Ecat/2 = −2.09 V vs Fc+/Fc confirmed its activity toward catalytic CO2 reduction. Product analysis via gas chromatography after 2 h showed the formation of CO with 100% selectivity, a TONCO of 6, and a Faradaic efficiency (FE) near unity (Table S3). Overall, the bulk activity and selectivity of [Re(NH2-bpy] closely match values for [Re(dmbpy)] and other known amino-substituted [Re(bpy)] complexes (Table S2).2,19,27 The amino group in [Re(NH2-bpy)] enables oxidative electrochemical grafting onto carbon electrode surfaces.28 We explored glassy carbon and colloid-imprinted carbon particles (CICs) as conductive support materials. The CICs used herein were prepared using a silica template method, leading to nanoporous particles with a BET-surface area of SBET = 134 m2

Figure 2. (A) Multiple CVs of a [Re(NH2-bpy)]-modified CIC electrode in ACN/TBAPF6 (0.1 M) electrolyte solution at 100 mV s−1. The last scan (scan 150) is shown in red. Inset: Correlation between the peak current density (jp) of the second redox wave and scan rate (v). The red trace represents a linear fit to the data points. (B) Change of [Re(NH2-bpy)] loading on glassy carbon (GC, black squares) and CIC electrodes (red circles) after multiple CV scans recorded under argon in dry ACN, and for CIC electrodes recorded under argon in ACN in the presence of ambient humidity (blue triangles). Loadings are referenced to the geometrical area of the electrode (A = 0.07 cm2). B


Letter


stability of [Re(NH2-bpy)] on the glassy carbon surface (Figures S17−S19) was observed, suggesting that Nafion is not simply functioning as a protective layer for the complex. Under a CO2 atmosphere, a large catalytic reduction wave at approximately Ecat/2 = −2.2 V vs Fc+/Fc indicated that [Re(NH2-bpy)] remained active upon immobilization of the complex on the CIC electrodes (Figure 3). When holding the

corresponds approximately to one monolayer of Re complex covering the flat glassy carbon surface (see SI for calculation). Similar coverages were achieved when using a glassy carbon plate or rod. The [Re(NH2-bpy)]-modified glassy carbon electrode was further analyzed by IR and X-ray photoelectron spectroscopy (XPS) to confirm the presence and integrity of the Re complex after the oxidative treatment (Figures S6− S13). The IR spectrum of anchored [Re(NH2-bpy)] showed a sharp signal at 2017 cm−1 and a broader peak at approximately 1900 cm−1, which are both also observed in the ATR IR spectrum of solid [Re(NH2-bpy)], and were assigned to the fac-CO ligand stretches (Figure S6). The XPS data showed the presence of Re at binding energies of 44.2 and 41.8 eV, which can be assigned as Re 4f5/2 and Re 4f7/2 levels, respectively (Table S4, Figures S7 and S9). The observed Re 4f energies match those of previously reported [Re(bpy)] complexes.6,8 For the C 1s and N 1s levels, a significant increase in intensity was observed at binding energies of 286.5 and 400.3 eV, respectively, which indicates the presence of additional C−N− C fragments due to the presence of the [Re(NH2-bpy)] complex on the glassy carbon electrode (Figures S10 and S11, Table S4). Integration of the Re 4f signal and the Cl 2p signals at 199.7 (2p1/2) and 198.1 eV (2p3/2) revealed a Re:Cl ratio of 1:0.8, confirming that the majority of the complex is present as [Re(NH2-bpy)(CO)3Cl] after the grafting procedure (Figure S13 and Table S4). The stability of the complex-modified glassy carbon electrodes was assessed via further electrochemical testing. Under the test protocol, they showed a high degree of instability, even under inert conditions under argon, leading to a complete loss of the redox and IR features related to the initially tethered [Re(NH2-bpy)] complex within the first 50 scans (Figure 2B, black trace; Figures S4 and S6). CVs of modified CIC electrodes in fresh ACN/TBAPF6 electrolyte solution under argon confirmed a stable hybrid electrode (Figure 2A) with a [Re(NH2-bpy)] loading of Γ[Re] = 5.6 ± 0.9 nmol cm−2 (Figure 2B, red trace; Γ determined after 100 scans; referenced to the geometrical area of the electrode A = 0.07 cm2). In comparison to glassy carbon, the complex loading was increased by a factor of 10 (0.42 vs 5.6 nmol cm−2). Taking into account SBET, a surface coverage of 10% was estimated for the CIC electrodes. It should be noted that SBET does not necessarily represent the electrochemically accessible surface area in this case, and the estimated coverages should be interpreted as reflecting a lower limit. The peak current density, jp, showed a linear dependency on the scan rate, v, confirming the presence of an adsorbed Re complex as opposed to a species freely diffusing in solution (Figure 2A, inset, and Figure S14).23 Experiments with [Re(dmbpy)] or in the absence of base provided evidence that the Re complex was not simply trapped in the nanoporous carbon network (Figures S15 and S16). The initial (∼60 cycles) apparent increase in coverage of the complex (Figure 2) was attributed to changes in the background current, most likely caused by the parallel reduction of residual solvent impurities (e.g., ethanol or i-propanol) present inside the catalyst layer from electrode preparation. Under argon atmosphere, the coverage was stable afterward, which is a marked improvement as compared to what is observed on glassy carbon (Figure 2). In order to elucidate the potential role of Nafion in the CIC ink on the stability, an additional layer of Nafion was added on top of the complex on the glassy carbon electrode. However, no further improvement in the

Figure 3. CVs of CIC|[Re(NH2-bpy)] recorded in ACN/TBAPF6 (0.1 M) under argon (black and gray) and CO2 (red) at 100 mV s−1. Corresponding background CVs are shown as dashed traces. Inset: Comparison of CVs before (black) and after (blue) testing of electrocatalytic CO2 reduction activity of CIC|[Re(NH2-bpy)] electrodes.

potential at Ecat/2 in a closed cell, CO was detected as the only gaseous product by GC with an FE of 92 ± 6% and an estimated Re-based turnover number for CO of approximately 900, when taking into account the catalyst loading on the CIC electrodes (vide supra). This corresponds to an improvement by approximately 2 orders of magnitude compared to the TONCO of the homogeneous system (vide supra). No CO or H2 was detected for CIC electrodes without any Re complex present (Table S3). Initially, current densities of up to jcat ≈ −15 mA cm−2 were reached under CO2; however, currents dropped quickly within the first 5 min of CPE or when running consecutive CV scans (Figure S20). A similar decrease in currents under catalytic conditions has been previously observed for grafted molecular CO2 reduction catalysts on carbon surfaces, but the exact cause has not been elucidated.5,16,19 A recent study by Marinescu et al. on a [Re(bpy)] complex polymerized onto various substrates concluded that partial leaching of the molecule into the electrolyte solution and structural rearrangement within the catalyst layer were the major factors contributing to the decrease in current densities and deactivation of the catalyst, respectively.8 Despite the fact that the oxidation of amines has been frequently reported to result in stable derivatization of carbon surfaces, electrodes have generally been probed under less reducing conditions than required for CO2 reduction in organic media. To investigate potential reasons for the observed decrease in catalyst features and current densities, we further examined the stability of CIC|[Re(NH2-bpy)] by testing the electrodes under various conditions in the presence of moisture or air. The modified electrodes were stable when stored under argon, and remained unchanged after exposure to air (Figure S21). Approximately 20% of the complex desorbed when storing electrodes in dry or wet ACN for 3 days, but no C


Letter


University of Alberta, Edmonton, are acknowledged for conducting XPS measurements. We thank Vinayaraj Ozhukil Kollath for help collecting ATR IR spectra.

further loss was observed in subsequent electrochemical stability tests in dry ACN/TBAPF6 electrolyte solution (Figure S21). When CVs were recorded in wet ACN under argon on the bench, the complex-related redox features decreased over time with the coverage dropping by over 50% within the first 100 scans (Figure 2B, blue trace). XPS data (Figure S22−S25) obtained for a GC|[Re(NH2-bpy)] electrode after electrochemical stability tests (vide supra) further showed a decline in all signals related to the Re complex (Table S4), with only a new minor Re-containing species detected (approximately 3%). Overall, we conclude that the observed instability is caused by an electrochemically induced hydrolysis or degradation process triggering breakage of the C−N bond between the carbon surface and the Re complex, or bonds in the proximity thereof, leading to leaching of the whole [Re(NH2-bpy)] complex into the bulk solution. Structural rearrangement or formation of Re-containing degradation products can be viewed as only a minor contribution to electrode deactivation. In conclusion, we have described a hybrid electrode for selective CO2 reduction based on a [Re(bpy)] catalyst tethered to a nanoporous colloid-imprinted carbon electrode for the first time. Further investigations are underway to elucidate the exact causes for the observed instability under CO2 in order to improve the anchoring of the molecular complex under catalytic conditions. Additional optimization in this context could involve studying other types of CICs with smaller or larger pore sizes, as well as modifying the CIC surface properties prior to catalyst attachment.

■

■

(1) Kondratenko, E. V.; Mul, G.; Baltrusaitis, J.; Larrazábal, G. O.; Pérez-Ramírez, J. Status and perspectives of CO2 conversion into fuels and chemicals by catalytic, photocatalytic and electrocatalytic processes. Energy Environ. Sci. 2013, 6, 3112−3135. (2) Clark, M. L.; Cheung, P. L.; Lessio, M.; Carter, E. A.; Kubiak, C. P. Kinetic and Mechanistic Effects of Bipyridine (bpy) Substituent, Labile Ligand, and Brønsted Acid on Electrocatalytic CO2 Reduction by Re(bpy) Complexes. ACS Catal. 2018, 8, 2021−2029. (3) Smieja, J. M.; Kubiak, C. P. Re(bipy-tBu)(CO)3Cl−improved Catalytic Activity for Reduction of Carbon Dioxide: IR-Spectroelectrochemical and Mechanistic Studies. Inorg. Chem. 2010, 49, 9283− 9289. (4) Hawecker, J.; Lehn, J.-M.; Ziessel, R. Electrocatalytic reduction of carbon dioxide mediated by Re(bipy)(CO)3Cl (bipy = 2,2′bipyridine). J. Chem. Soc., Chem. Commun. 1984, 0, 328−330. (5) Zhanaidarova, A.; Ostericher, A. L.; Miller, C. J.; Jones, S. C.; Kubiak, C. P. Selective Reduction of CO2 to CO by a Molecular Re(ethynyl-bpy)(CO)3Cl Catalyst and Attachment to Carbon Electrode Surfaces. Organometallics 2019, 38, 1204. (6) Oh, S.; Gallagher, J. R.; Miller, J. T.; Surendranath, Y. GraphiteConjugated Rhenium Catalysts for Carbon Dioxide Reduction. J. Am. Chem. Soc. 2016, 138, 1820−1823. (7) Schreier, M.; Luo, J.; Gao, P.; Moehl, T.; Mayer, M. T.; Grätzel, M. Covalent Immobilization of a Molecular Catalyst on Cu2O Photocathodes for CO2 Reduction. J. Am. Chem. Soc. 2016, 138, 1938−1946. (8) Orchanian, N. M.; Hong, L. E.; Skrainka, J. A.; Esterhuizen, J. A.; Popov, D. A.; Marinescu, S. C. Surface-Immobilized Conjugated Polymers Incorporating Rhenium Bipyridine Motifs for Electrocatalytic and Photocatalytic CO2 Reduction. ACS Appl. Energy Mater. 2019, 2, 110−123. (9) Blakemore, J. D.; Gupta, A.; Warren, J. J.; Brunschwig, B. S.; Gray, H. B. Noncovalent Immobilization of Electrocatalysts on Carbon Electrodes for Fuel Production. J. Am. Chem. Soc. 2013, 135, 18288−18291. (10) Reuillard, B.; Ly, K. H.; Rosser, T. E.; Kuehnel, M. F.; Zebger, I.; Reisner, E. Tuning Product Selectivity for Aqueous CO2 Reduction with a Mn(bipyridine)-pyrene Catalyst Immobilized on a Carbon Nanotube Electrode. J. Am. Chem. Soc. 2017, 139, 14425− 14435. (11) Bullock, R. M.; Das, A. K.; Appel, A. M. Surface Immobilization of Molecular Electrocatalysts for Energy Conversion. Chem. - Eur. J. 2017, 23, 7626−7641. (12) Andreiadis, E. S.; Jacques, P.-A.; Tran, P. D.; Leyris, A.; Chavarot-Kerlidou, M.; Jousselme, B.; Matheron, M.; Pécaut, J.; Palacin, S.; Fontecave, M.; Artero, V. Molecular engineering of a cobalt-based electrocatalytic nanomaterial for H2 evolution under fully aqueous conditions. Nat. Chem. 2013, 5, 48−53. (13) Reuillard, B.; Warnan, J.; Leung, J. J.; Wakerley, D. W.; Reisner, E. A Poly(cobaloxime)/Carbon Nanotube Electrode: Freestanding Buckypaper with Polymer-Enhanced H2-Evolution Performance. Angew. Chem., Int. Ed. 2016, 55, 3952−3957. (14) Wadsworth, B. L.; Beiler, A. M.; Khusnutdinova, D.; Jacob, S. I.; Moore, G. F. Electrocatalytic and Optical Properties of Cobaloxime Catalysts Immobilized at a Surface-Grafted Polymer Interface. ACS Catal. 2016, 6, 8048−8057. (15) Zhang, X.; Wu, Z.; Zhang, X.; Li, L.; Li, Y.; Xu, H.; Li, X.; Yu, X.; Zhang, Z.; Liang, Y.; Wang, H. Highly selective and active CO2 reduction electrocatalysts based on cobalt phthalocyanine/carbon nanotube hybrid structures. Nat. Commun. 2017, 8, 14675. (16) Elgrishi, N.; Griveau, S.; Chambers, M. B.; Bedioui, F.; Fontecave, M. Versatile functionalization of carbon electrodes with a

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsaem.9b00216. Experimental details including synthesis and characterization, crystallographic data, and supporting figures and tables (PDF) Accession Codes

CCDC 1894464 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: + 44 1223 336033.

■

REFERENCES

AUTHOR INFORMATION

Corresponding Authors

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

Janina Willkomm: 0000-0002-8980-2944 Warren E. Piers: 0000-0003-2278-1269 Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS This research was undertaken thanks to funding from the Canada First Research Excellence Fund (CFREF). The 4D laboratories facility at the Simon Fraser University, Burnaby, and the NanoFAB fabrication & characterization facility at the D


Letter

ACS Applied Energy Materials polypyridine ligand: metallation and electrocatalytic H+ and CO2 reduction. Chem. Commun. 2015, 51, 2995−2998. (17) Zhanaidarova, A.; Moore, C. E.; Gembicky, M.; Kubiak, C. P. Covalent attachment of [Ni(alkynyl-cyclam)]2+ catalysts to glassy carbon electrodes. Chem. Commun. 2018, 54, 4116−4119. (18) Downard, A. J. Electrochemically Assisted Covalent Modification of Carbon Electrodes. Electroanalysis 2000, 12, 1085−1096. (19) Sun, C.; Rotundo, L.; Garino, C.; Nencini, L.; Yoon, S. S.; Gobetto, R.; Nervi, C. Electrochemical CO2 Reduction at Glassy Carbon Electrodes Functionalized by MnI and ReI Organometallic Complexes. ChemPhysChem 2017, 18, 3219−3229. (20) Li, Z.; Jaroniec, M. Synthesis and Adsorption Properties of Colloid-Imprinted Carbons with Surface and Volume Mesoporosity. Chem. Mater. 2003, 15, 1327−1333. (21) Banham, D.; Feng, F.; Fürstenhaupt, T.; Pei, K.; Ye, S.; Birss, V. Novel Mesoporous Carbon Supports for PEMFC Catalysts. Catalysts 2015, 5, 1046−1067. (22) Antolini, E. Carbon supports for low-temperature fuel cell catalysts. Appl. Catal., B 2009, 88, 1−24. (23) Abruña, H. D. Coordination chemistry in two dimensions: chemically modified electrodes. Coord. Chem. Rev. 1988, 86, 135− 189. (24) Appel, A. M.; Helm, M. L. Determining the Overpotential for a Molecular Electrocatalyst. ACS Catal. 2014, 4, 630−633. (25) Lee, K. J.; Elgrishi, N.; Kandemir, B.; Dempsey, J. L. Electrochemical and spectroscopic methods for evaluating molecular electrocatalysts. Nat. Rev. Chem. 2017, 1, 0039. (26) Azcarate, I.; Costentin, C.; Robert, M.; Savéant, J.-M. Dissection of Electronic Substituent Effects in Multielectron− Multistep Molecular Catalysis. Electrochemical CO2-to-CO Conversion Catalyzed by Iron Porphyrins. J. Phys. Chem. C 2016, 120, 28951−28960. (27) Popov, D. A.; Luna, J. M.; Orchanian, N. M.; Haiges, R.; Downes, C. A.; Marinescu, S. C. A 2,2′-bipyridine-containing covalent organic framework bearing rhenium(i) tricarbonyl moieties for CO2 reduction. Dalton Transactions 2018, 47, 17450−17460. (28) Buriez, O.; Labbé, E.; Pigeon, P.; Jaouen, G.; Amatore, C. Electrochemical attachment of a conjugated amino−ferrocifen complex onto carbon and metal surfaces. J. Electroanal. Chem. 2008, 619−620, 169−175. (29) Atwa, M.; Loung, S.; Li, X.; Forouzandeh, F.; Sui, R.; Marriott, R.; Birss, V. In preparation, 2019. (30) Sandroni, M.; Volpi, G.; Fiedler, J.; Buscaino, R.; Viscardi, G.; Milone, L.; Gobetto, R.; Nervi, C. Iridium and ruthenium complexes covalently bonded to carbon surfaces by means of electrochemical oxidation of aromatic amines. Catal. Today 2010, 158, 22−28.

E


Grafting of a Molecular Rhenium CO2 Reduction Catalyst onto Colloid

Recommend Documents