Increasing the rate of hydrogen oxidation without increasing the overpotential: a bio-inspired iron molecular electrocatalyst with an outer coordination sphere proton relay

Abstract

H2 oxidation by a molecular electrocatalyst is dramatically improved by controlling proton movement from iron to the outer coordination sphere.

Thermodynamic Insights on a Bistable Acid–Base Switchable Molecular Shuttle with Strongly Shifted Co‐conformational Equilibria

“…The titration of Rot 1s with a base can provide information on the acid–base properties of the amm + site when it is surrounded by DB24C8 (vertical process in the right hand part of Scheme ). Indeed, no spectroscopic modification could be observed when Rot 1s was treated with a huge excess of 1,4‐diazabicyclo[2.2.2]octane (DABCO, p K a =18.2) . This observation indicates that the p K a of the amm + unit encircled by DB24C8 is larger than 23.9…”

A pendant proton shuttle on [Fe4N(CO)12]−alters product selectivity in formate vs. H2production via the hydride [H–Fe4N(CO)12]−

“…Proton relays also enhance rates, decrease overpotentials and promote already selective reactions 7,8. For instance, molecular electrocatalysts with pendant amine bases generate hydrogen with up to 106 000 turnovers per s,9 and “Hangman” porphyrin complexes exhibit lowered proton reduction overpotentials and increased rates 10.…”

A New Redox Mediator (Cupric‐Neocuproine Complex)‐ Modified Pencil Graphite Electrode for the Electrocatalytic Oxidation of H2O2: A Flow Injection Amperometric Sensor

“…These results showed that the electrocatalytic oxidation of H 2 O 2 at modified electrode is controlled by diffusion process in which a chemical reaction has taken place between diffused H 2 O 2 and [Cu(Nc) 2 ] 2+ on the electrode surface. The turnover frequency (TOF) for the electrocatalytic oxidation of H 2 O 2 was calculated by using the equation of [ I cat / I p =( n /0.4463)×( RTk obs / Fν ) 1/2 ] described in the literature, where I p and I cat are the currents under non‐catalytic and catalytic conditions, n is electron number, and k obs is the observed first‐order rate constant (TOF). This value was determined to be 6800 s −1 at 0.5 V/s in the presence of 1.0 mM H 2 O 2 at a half‐wave potential (E cat/2 ) of 0.33 V.…”