Electrochemical oxidation of CO on Au in alkaline solution

Kita, Hideaki; Nakajima, Hiroshi; Hayashi, Kimitaka

doi:10.1016/0022-0728(85)80083-8

Cited by 90 publications

(62 citation statements)

References 13 publications

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“…In Fig. 2, solid line, the first cyclic voltammogram (CV) scan initiated after CDR catalysis on the RCE at −0.80 V displays a broad oxidation wave spanning −0.20 to 0.80 V, in line with reported potentials for twoelectron CO oxidation to CO 2 on Au surfaces (66,67,(75)(76)(77)(78). On subsequent cycling (Fig.…”

Section: Resultssupporting

confidence: 57%

“…1C) or codosed (Fig. 1G), CO bridge remains on the Au surface up until potentials are sufficiently positive to induce its two-electron oxidative desorption as CO 2 (see the following paragraph) (66,67,(75)(76)(77)(78). Notably, the irreversibility of CO bridge adsorption promotes its formation 510 mV positive of the thermodynamic E 0 of CDR to CO g (−0.51 V) under these conditions (Fig.…”

Section: Resultsmentioning

confidence: 99%

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Inhibited proton transfer enhances Au-catalyzed CO ₂ -to-fuels selectivity

Wuttig

Yaguchi

Motobayashi

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

363

480

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CO 2 reduction in aqueous electrolytes suffers efficiency losses because of the simultaneous reduction of water to H 2 . We combine in situ surface-enhanced IR absorption spectroscopy (SEIRAS) and electrochemical kinetic studies to probe the mechanistic basis for kinetic bifurcation between H 2 and CO production on polycrystalline Au electrodes. Under the conditions of CO 2 reduction catalysis, electrogenerated CO species are irreversibly bound to Au in a bridging mode at a surface coverage of ∼0.2 and act as kinetically inert spectators. Electrokinetic data are consistent with a mechanism of CO production involving rate-limiting, single-electron transfer to CO 2 with concomitant adsorption to surface active sites followed by rapid one-electron, two-proton transfer and CO liberation from the surface. In contrast, the data suggest an H 2 evolution mechanism involving rate-limiting, single-electron transfer coupled with proton transfer from bicarbonate, hydronium, and/or carbonic acid to form adsorbed H species followed by rapid one-electron, one-proton, or H recombination reactions. The disparate proton coupling requirements for CO and H 2 production establish a mechanistic basis for reaction selectivity in electrocatalytic fuel formation, and the high population of spectator CO species highlights the complex heterogeneity of electrode surfaces under conditions of fuel-forming electrocatalysis.carbon dioxide reduction | catalyst selectivity | in situ spectroscopy | proton-coupled electron transfer P roduct selectivity is a principal design consideration for the development of practical catalysts. Catalyst selectivity is dictated by (i) the relative free energy barriers for progress along competing reaction pathways and (ii) the relative rates of reactant delivery to active sites (1). Enzymes fine tune these parameters with exquisite precision to achieve selectivity (2). Nature augments the coordination environment of metallocofactor active sites to optimize the binding strengths of reaction partners and preorganizes reaction participants toward low-barrier pathways (3). Additionally, many active sites reside at the terminus of molecular channels that gate the coordinated delivery of substrates (4, 5) required for selective transformations. Efforts to prepare artificial catalysts with product selectivities rivaling that of nature require a detailed understanding of these factors.Currently, our understanding of how to systematically modulate selectivity in heterogeneous catalysts remains poor (6-8). Unlike (bio)molecular catalysts, which ideally consist of a uniform ensemble of active sites, heterogeneous catalysts consist of a nonuniform distribution of surface sites (9), requiring an understanding of which are active and which are dormant. The surface site distribution is strongly dependent on the surface nanostructure, oxidation state, and degree of restructuring (7). Superimposed on this distribution are the rate-limiting elementary reaction steps that dictate kinetic branching ratios at surface active sites (1...

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Section: Resultssupporting

confidence: 57%

Section: Resultsmentioning

confidence: 99%

Inhibited proton transfer enhances Au-catalyzed CO ₂ -to-fuels selectivity

Wuttig

Yaguchi

Motobayashi

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

363

480

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“…A broad oxidative feature is observed beginning at 0.60 V ( Figure 1F, red), which we attribute to the oxidation of surface adsorbed CO formed during electrolysis. 58 We speculate that in untreated electrolytes, this weak feature is masked by the copper stripping wave.…”

Section: Resultsmentioning

confidence: 89%

Impurity Ion Complexation Enhances Carbon Dioxide Reduction Catalysis

2015

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Herein, we show that group 11 CO 2 reduction catalysts are rapidly poisoned by progressive deposition of trace metal ion impurities existent in high purity electrolytes. Metal impurity deposition was characterized by XPS and in situ stripping voltammetry and is coincident with loss of catalytic activity and selectivity for CO 2 reduction, favoring hydrogen evolution on poisoned surfaces. Metal deposition can be suppressed by complexing trace metal-ion impurities with ethylenediaminetetraacetic acid or solid supported iminodiacetate resins. Metal ion complexation allows for reproducible, sustained catalytic activity and selectivity for CO 2 reduction on Au, Ag, and Cu electrodes. Together, this study establishes the principle mode by which group 11 CO 2 reduction catalysts are poisoned and lays out a general approach for extending the lifetime of electrocatalysts subject to impurity metal deposition.

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“…It is not just that unstable states of metals and ill-defined oxyspecies are involved; it also appears that for a given electrode system there is a selection or range of transitions. It may be noted that similar ideas were proposed earlier for platinum in acid (34) and the same type of behaviour was observed recently (39) The discussion of electrocatalysis here is confined largely to gold in acid; however, it is worth noting that with gold in base carbon monoxide oxidation commences at an even lower potential, ca 0.1 V, than in acid, ca 0.5 V; the voltammetric responses, for the two different electrolyte solutions, are given ( Figure 5) in the work of Kita and coworkers (40). The nature of the redox transition at ca 0.1 V for gold in base was discussed earlier (7). )…”

Section: Surface and Interfacial Catalysismentioning

confidence: 92%

High energy states of goldand their importance in electrocatalytic processes at surfaces and interfaces

2002

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The ability of metals to store or trap considerable amounts of energy, and thus exist in a non-equilibrium or metastable state, is very well known in metallurgy; however, such behaviour, which is intimately connected with the defect character of metals, has been largely ignored in noble metal surface electrochemistry. Techniques for generating unusually high energy surface states for gold, and the unusual voltammetric responses of such states, are outlined. The surprisingly high (and complex) electrocatalytic activity of gold in aqueous media is attributed to the presence of a range of such non-equilibrium states as the vital entities at active sites on conventional gold surfaces. The possible relevance of these ideas to account for the remarkable catalytic activity of oxidesupported gold microparticles is briefly outlined.From a technological viewpoint heterogeneous catalysis is one of the most important areas of chemistry; in new technology such processes are responsible for over 90% of chemical and petroleum products by value (1). It is widely accepted (1) that a vital objective in this area is to identify the nature and mode of operation of surface active sites; this task was designated recently by Roberts (2) as "the ultimate in catalytic research". The problems involved appear quite daunting as, despite extensive investigation involving a vast array of sophisticated techniques, the general impression (for the vast majority of catalytic processes) is that "catalytic sites remain unidentified" (3).The active site theory of heterogeneous catalysis was proposed by Taylor (4) in 1925. Along with the suggestion that only a small percentage of surface atoms participate in such reactions, he pointed out that the sites in question "manifest an extraordinary sensitivity to heat treatment". He attributed the latter to the incomplete crystallization of the active site material, ie the latter (as discussed here later) usually exists in a metastable, non-equilibrium state. By inducing crystallization, the heat treatment eliminates the active sites and the resulting more stable material produced at the surface is relatively inactive. Taylor's suggestions are in agreement with current ideas in the surface science approach to surface catalysis, eg Somorjai (5) pointed out recently that, for the same surface, catalytic processes occur much more rapidly at defects (the metal atoms (Med) associated with defects are intrinsically active, ie μ(Med) > μ°(Me)), such as kinks and ledges, than on terraces; he also stressed that "rough [disordered or non-equilibrated] surfaces do chemistry", ie they are the most active from a catalytic viewpoint.In the present article the main emphasis is on electrocatalysis, ie the catalysis of faradaic reactions, and in particular on the behaviour of gold in aqueous media. This work may be regarded as an extension of an earlier 2-part review (6, 7) of the electrocatalytic properties of the same metal. Attention is focused on such topics as metastable, non-equilibrium or defect states of metals, me...

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Electrochemical oxidation of CO on Au in alkaline solution

Cited by 90 publications

References 13 publications

Inhibited proton transfer enhances Au-catalyzed CO ₂ -to-fuels selectivity

Inhibited proton transfer enhances Au-catalyzed CO ₂ -to-fuels selectivity

Impurity Ion Complexation Enhances Carbon Dioxide Reduction Catalysis

High energy states of goldand their importance in electrocatalytic processes at surfaces and interfaces

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Electrochemical oxidation of CO on Au in alkaline solution

Cited by 90 publications

References 13 publications

Inhibited proton transfer enhances Au-catalyzed CO 2 -to-fuels selectivity

Inhibited proton transfer enhances Au-catalyzed CO 2 -to-fuels selectivity

Impurity Ion Complexation Enhances Carbon Dioxide Reduction Catalysis

High energy states of goldand their importance in electrocatalytic processes at surfaces and interfaces

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Product

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Inhibited proton transfer enhances Au-catalyzed CO ₂ -to-fuels selectivity

Inhibited proton transfer enhances Au-catalyzed CO ₂ -to-fuels selectivity