Molecular electrocatalysis at soft interfaces

Abstract

The fundamental aspects of electrochemistry at liquid-liquid interfaces are introduced to present the concept of molecular electrocatalysis. Here, a molecular catalyst is adsorbed at the interface to promote a proton coupled electron transfer reaction such as hydrogen evolution or oxygen reduction using lipophilic electron donors.

Oxygen Reduction at Soft Interfaces Catalyzed by In Situ‐Generated Reduced Graphene Oxide

“…(2)- (4)]. This mechanism of quinone-mediated reduction of molecular O 2 to H 2 O 2 is consistent with previous reports for O 2 reduction at quinone-modified electrode surfaces. [5,23] RGO À Q þ e À !…”

“…The current wave at positive potentials varies linearly with the square root of the scan rate (data not shown), indicating that this process is limited by the diffusion of DMFc to the interface, as all other species are in excess. On replacing DMFc (standard redox potential in DCE versus the aqueous standard hydrogen electrode (SHE), [17] with a weaker reductant such as Fc (½E 0 [2] the current wave associated with the PCET process is no longer evident, as it is shifted in a positive direction, that is, outside of the available potential window, because of the difference between the redox potentials of DMFc and Fc. Nonetheless, an enhanced production of ferrocenium ions (Fc + ) in the presence of GO was clearly observed by iontransfer voltammetry (see Figure SI tion of GO to RGO and, as shown vide infra, the subsequent PCET process).…”

“…[1] Liquid/liquid interfaces provide a unique platform at which to study ORRs, at which aqueous protons react with organic solubilized electron donors in the absence or presence of adsorbed catalysts, usually through a proton-coupled electron-transfer (PCET) reaction. [2] The molecular catalysts studied include cobalt, [3] free-base porphyrins, [4] and in situ-deposited platinum particles. [5] The ORR proceeds either by a 4 e À /4 H + pathway to produce water or a 2 e À /2 H + route to yield H 2 O 2 , which is considered a green oxidant.…”

Artificial Photosynthesis at Soft Interfaces

“…In this respect, Proton Coupled Electron Transfer (PCET) reactions represent an interesting case, as it is possible to react a molecule located at the interface both with aqueous protons and with lipophilic electron donors. [11] Hydrogen Evolution at LiquidLiquid Interfaces…”

Reactivity and Dynamics at Liquid Interfaces

“…Prominent among these are non-linear spectroscopic techniques such as Second Harmonic Generation (SHG) and Sum Frequency Generation (SFG), which probe the surface region selectively. [13][14][15] These techniques have been used to explore the liquid/vapor interface [16][17][18] and buried interfaces, such as liquid/liquid [19][20][21][22][23][24] and liquid/solid interfaces, [25][26][27][28][29] as well as biological interfaces. 30,31 Other techniques that have been used in recent years to study liquid surfaces and interfaces include light scattering, 32-36 X-ray and neutron scattering, 34,[37][38][39][40][41][42][43][44] atomic scattering, 45 fluorescence anisotropy decay, 46,47 scanning electrochemical microscopy, 48,49 infrared spectroscopy in a total reflection geometry 50,51 and X-ray absorption spectroscopy.…”