Indian Association for the Cultivation of Science

About: Indian Association for the Cultivation of Science is a education organization based out in Kolkata, India. It is known for research contribution in the topics: Catalysis & Excited state. The organization has 3867 authors who have published 10457 publications receiving 220098 citations.

Rational Design of Mononuclear Iron Porphyrins for Facile and Selective 4e–/4H+ O2 Reduction: Activation of O–O Bond by 2nd Sphere Hydrogen Bonding

Abstract: Facile and selective 4e–/4H+ electrochemical reduction of O2 to H2O in aqueous medium has been a sought-after goal for several decades Elegant but synthetically demanding cytochrome c oxidase mimics have demonstrated selective 4e–/4H+ electrochemical O2 reduction to H2O is possible with rate constants as fast as 105 M–1 s–1 under heterogeneous conditions in aqueous media Over the past few years, in situ mechanistic investigations on iron porphyrin complexes adsorbed on electrodes have revealed that the rate and selectivity of this multielectron and multiproton process is governed by the reactivity of a ferric hydroperoxide intermediate The barrier of O—O bond cleavage determines the overall rate of O2 reduction and the site of protonation determines the selectivity In this report, a series of mononuclear iron porphyrin complexes are rationally designed to achieve efficient O—O bond activation and site-selective proton transfer to effect facile and selective electrochemical reduction of O2 to water In

Factors Determining the Rate and Selectivity of 4e–/4H+ Electrocatalytic Reduction of Dioxygen by Iron Porphyrin Complexes

Abstract: ConspectusReactivity as well as selectivity are crucial in the activation and electrocatalytic reduction of molecular oxygen. Recent developments in the understanding of the mechanism of electrocatalytic O2 reduction by iron porphyrin complexes in situ using surface enhanced resonance Raman spectroscopy coupled to rotating disc electrochemistry (SERRS-RDE) in conjunction with H/D isotope effects on electrocatalytic current reveals that the rate of O2 reduction, ∼104 to 105 M–1 s–1 for simple iron porphyrins, is limited by the rate of O–O bond cleavage of an intermediate ferric peroxide species (FeIII–OOH). SERRS-RDE probes the system in operando when it is under steady state such that any intermediate species that has a greater rate of formation relative to its rate of decay, including the rate determining species, would accumulate and can be identified. This technique is particularly well suited to investigate iron porphyrin electrocatalysts as the intense symmetric ligand vibrations allow determination ...