scholarly journals Atomically manipulated proton transfer energizes water oxidation on silicon carbide photoanodes

2018 ◽  
Vol 6 (47) ◽  
pp. 24358-24366 ◽  
Author(s):  
Hao Li ◽  
Huan Shang ◽  
Yuchen Shi ◽  
Rositsa Yakimova ◽  
Mikael Syväjärvi ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Electron Transfer ◽  
Proton Transfer ◽  
Water Oxidation ◽  
Proton Coupled Electron Transfer ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting

Preferential exposure of Si-face of SiC will mechanistically shift the rate limiting step of water oxidation from sluggish proton-coupled electron transfer on C-face to a more energy-favorable electron transfer.

The rate-limiting step in the thermal oxidation of silicon carbide

2010 ◽  
Vol 62 (9) ◽  
pp. 654-657 ◽  
Author(s):  
Junjie Wang ◽  
Litong Zhang ◽  
Qingfeng Zeng ◽  
Gérard L. Vignoles ◽  
Laifei Cheng ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Thermal Oxidation ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting

Base-catalyzed formation of spiro adduct from N-methyl-N-(2,4,6-trinitrophenyl)glycinamide, the smiles rearrangement of the amide in methanol

1988 ◽  
Vol 53 (3) ◽  
pp. 601-618 ◽  
Author(s):  
Jaromír Kaválek ◽  
Vladimír Macháček ◽  
Makky M. M. Hassanien ◽  
Vojeslav Štěrba
Keyword(s):  
Proton Transfer ◽  
Equilibrium Constant ◽  
Ammonium Salt ◽  
Aliphatic Amine ◽  
Reaction Pathway ◽  
Smiles Rearrangement ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting ◽  
Kinetics Of

The reaction of N-methyl-N-(2,4,6-trinitrophenyl)glycinamide (Ic with methoxide in methanol produces the spiro adduct IIc(A). In methanolic acetate buffers, the equilibrium is rapidly established between the spiro adduct IIc(A) and the dipolar ion of 2-methylamino-N-(2,4,6-trinitrophenyl)acetamide (IIIc(Z)). The equilibrium constant of the reaction IIIc(Z) ⇆ IIc(A) + H+ is by eight orders of magnitude greater than that of the analogous cyclization of 2-methylamino-N-methyl-N-(2,4,6-trinitrophenyl)acetamide to the spiro adduct. In chloracetate buffers, the dipolar ion is protonated to give 2-methylammonium-N-(2,4,6-trinitrohenyl)acetamide IIIc(K). The kinetics of the reversible reaction IIIc(Z) ⇆ IIc(A) + H+ has been studied in acetate buffers, aliphatic amine – ammonium salt buffers, and methoxide solutions. In all cases, the rate-limiting step was the proton transfer with half-lives in milliseconds. In more basic methanolic buffers (pH > 10) the rate-limiting step consists in the formation of spiro adduct from the zwiterion IIIc(Z) resulting from the protonation of the anion IIIc(A). n acetate buffers, the second reaction pathway via the cation IIIc(K) is predominant.

scholarly journals Design and synthesis of benzimidazole phenol-porphyrin dyads for the study of bioinspired photoinduced proton-coupled electron transfer

2019 ◽  
Vol 23 (11n12) ◽  
pp. 1336-1345
Author(s):  
S. Jimena Mora ◽  
Daniel A. Heredia ◽  
Emmanuel Odella ◽  
Uma Vrudhula ◽  
Devens Gust ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Photosystem Ii ◽  
Proton Transfer ◽  
Water Oxidation ◽  
Oxidation Catalyst ◽  
Design And Synthesis ◽  
Proton Coupled Electron Transfer ◽  
Anchoring Groups ◽  
High Redox Potential

Benzimidazole phenol-porphyrin dyads have been synthesized to study proton-coupled electron transfer (PCET) reactions induced by photoexcitation. High-potential porphyrins have been chosen to model P680, the photoactive chlorophyll cluster of photosynthetic photosystem II (PSII). They have either two or three pentafluorophenyl groups at the meso positions to impart the high redox potential. The benzimidazole phenol (BIP) moiety models the Tyr[Formula: see text]-His190 pair of PSII, which is a redox mediator that shuttles electrons from the water oxidation catalyst to P680[Formula: see text]. The dyads consisting of a porphyrin and an unsubstituted BIP are designed to study one-electron one-proton transfer (E1PT) processes upon excitation of the porphyrin. When the BIP moiety is substituted with proton-accepting groups such as imines, one-electron two-proton transfer (E2PT) processes are expected to take place upon oxidation of the phenol by the excited state of the porphyrin. The bis-pentafluorophenyl porphyrins linked to BIPs provide platforms for introducing a variety of electron-accepting moieties and/or anchoring groups to attach semiconductor nanoparticles to the macrocycle. The triads thus formed will serve to study the PCET process involving the BIPs when the oxidation of the phenol is achieved by the photochemically produced radical cation of the porphyrin.

scholarly journals Spectroelectrochemical study of water oxidation on nickel and iron oxyhydroxide electrocatalysts

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Laia Francàs ◽  
Sacha Corby ◽  
Shababa Selim ◽  
Dongho Lee ◽  
Camilo A. Mesa ◽  
...  
Keyword(s):  
Water Oxidation ◽  
Reactive Intermediates ◽  
Reaction Rates ◽  
Iron Oxyhydroxide ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Earth Abundant ◽  
Fe Oxyhydroxides ◽  
Rate Limiting ◽  
Kinetics Of

AbstractNi/Fe oxyhydroxides are the best performing Earth-abundant electrocatalysts for water oxidation. However, the origin of their remarkable performance is not well understood. Herein, we employ spectroelectrochemical techniques to analyse the kinetics of water oxidation on a series of Ni/Fe oxyhydroxide films: FeOOH, FeOOHNiOOH, and Ni(Fe)OOH (5% Fe). The concentrations and reaction rates of the oxidised states accumulated during catalysis are determined. Ni(Fe)OOH is found to exhibit the fastest reaction kinetics but accumulates fewer states, resulting in a similar performance to FeOOHNiOOH. The later catalytic onset in FeOOH is attributed to an anodic shift in the accumulation of oxidised states. Rate law analyses reveal that the rate limiting step for each catalyst involves the accumulation of four oxidised states, Ni-centred for Ni(Fe)OOH but Fe-centred for FeOOH and FeOOHNiOOH. We conclude by highlighting the importance of equilibria between these accumulated species and reactive intermediates in determining the activity of these materials.

Is the Internal Electron Transfer the Rate-Limiting Step in the Catalytic Cycle of Cytochrome c Oxidase?

1988 ◽  
Vol 550 (1 Cytochrome Ox) ◽  
pp. 161-166 ◽  
Author(s):  
PAOLO SARTI ◽  
GIOVANNI ANTONINI ◽  
RANCESCO MALATESTA ◽  
BEATRICE VALLONE ◽  
MAURIZIO BRUNORI
Keyword(s):  
Electron Transfer ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Catalytic Cycle ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Internal Electron ◽  
Rate Limiting
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