Electrochemical Formation of Fe(IV)=O Derived from H₂O₂ on a Hematite Electrode as an Active Catalytic Site for Selective Hydrocarbon Oxidation Reactions

Abstract

The high‐valence iron species (Fe(IV)=O) in the cytochrome P450 enzyme superfamily is generated via the activation of O2, and serves as the active center of selective hydrocarbon oxidation reactions. Furthermore, P450 can employ an alternate route to produce Fe(IV)=O, even from H2O2 without O2 activation. Meanwhile, Fe(IV)=O has recently been revealed to be the reactive intermediate during H2O oxidation to O2 on hematite electrodes. Herein, we demonstrated the generation of Fe(IV)=O on hematite electrodes during the electrochemical oxidative decomposition of H2O2 using in situ UV‐visible absorption spectra. The generation of Fe(IV)=O on hematite electrodes from H2O2 exhibited 100 mV lower overpotential than that from H2O. This is because H2O2 serves not only as the oxygen source of Fe(IV)=O, but also as the additional oxidant. Finally, we confirmed that the Fe(IV)=O generated on hematite electrodes can serve as the catalytic site for styrene epoxidation reactions.

Induction of Concerted Proton-Coupled Electron Transfer during Oxygen Evolution on Hematite Using Lanthanum Oxide as a Solid Proton Acceptor

“…The rate-determining step of the OER on α-Fe 2 O 3 was revealed to be Fe 4+ formation in previous spectroelectrochemical studies. ,,,− Although this process usually proceeded through the stepwise ET–PT mechanism at neutral pH, the addition of an appropriate proton acceptor to the electrolyte changed it to the CPET mechanism owing to the acceleration of PT . On the basis of the libido rule, , which explains the conditions necessary for the acceleration of PT and the protonation properties of hydroxyl and oxo groups of α-Fe 2 O 3 associated with Fe 4+ formation, , a proton acceptor with a p K a value from 4 to 10 was demonstrated to be suitable for the CPET induction .…”

Aqueous Electrochemical Partial Oxidation of Gaseous Ethylbenzene by a Ru-Modified Covalent Triazine Framework

“…A high-valency Ru-oxo (RuO) species, which is generated by two-electron water oxidation, is the active center for the oxidation of organic substrates. High-valent metal-oxo species are known to efficiently catalyze a net O-atom insertion into C–H bonds in hydrocarbons. ,− Thus, the RuO species with high oxidation power facilitates O-atom insertion into C–H of EB to form 1-phenylethanol. The adsorbed alcohol is then further oxidized to acetophenone via the 2-electron transfer step .…”

Advanced hematite nanomaterials for newly emerging applications

“…In other words, they can be further oxidized into Fe(IV) and/or reduced to Fe(II)/Fe(0) species under suitable external conditions. [57][58][59][60] The redox activity makes it feasible in energy-related elds (Fig. 2f).…”