Peili Zhang

A super-efficient cobalt catalyst for electrochemical hydrogen production from neutral water with 80 mV overpotential

Self-assembled molecular iron and cobalt catalysts (MP4N2, M = Fe, Co) bearing a multihydroxy-functionalized tetraphosphine ligand electrocatalyze H2 generation from neutral water on a mercury electrode at −1.03 and −0.50 V vs. NHE, respectively. Complex CoP4N2 displays extremely low overpotential (Eonset = 80 mV) while maintaining high activity and good stability. Bulk electrolysis of CoP4N2 in a neutral phosphate buffer solution at −1.0 V vs. NHE produced 9.24 × 104 mol H2 per mol cat. over 20 h, with a Faradaic efficiency close to 100% and without apparent deactivation.

Electrocatalytic hydrogen evolution from neutral water by molecular cobalt tripyridine–diamine complexes

A cobalt complex with a tripyridine-diamine pentadentate ligand was found to be a highly active catalyst for electrochemical H2 production from neutral water, with an activity of 860 mol H2 (mol cat)(-1) h(-1) (cm(2) Hg)(-1) over 60 h CPE experiment at -1.25 V in a pH 7 phosphate buffer solution, without considerable deactivation.

Multielectron-Transfer Templates via Consecutive Two-Electron Transformations: Iron–Sulfur Complexes Relevant to Biological Enzymes

[FeFe] hydrogenase mimics: two polynuclear iron-sulfur complexes (1 and 2) were prepared and structurally characterized. They are potentially effective and stable multielectron-transfer relays for mediating four- and six-electron transformations via a cascade of reversible two-electron redox steps with relatively narrow potential spans.

Tetranuclear Iron Complexes Bearing Benzenetetrathiolate Bridges as Four-Electron Transformation Templates and Their Electrocatalytic Properties for Proton Reduction

Two tetranuclear iron-sulfur complexes, (μ,μ-pbtt)[Fe(2)(CO)(6)](2) (pbtt = benzene-1,2,4,5-tetrathiolato, 3) and (μ,μ-obtt)[Fe(2)(CO)(6)](2) (obtt = benzene-1,2,3,4-tetrathiolato, 4), were prepared from reaction of Fe(3)(CO)(12) and the corresponding tetramercaptobenzene in THF, respectively. Complexes 5 and 6, (μ,μ-pbtt)[Fe(2)(CO)(5)L(1)][Fe(2)(CO)(5)L(2)] (L(1) = CO, L(2) = PPyr(3) (Pyr = N-pyrrolyl), 5; L(1) = L(2) = PPyr(3), 6) were obtained by controlling CO displacement of 3 with PPyr(3). Molecular structures of 3-6 were determined by spectroscopic and single-crystal X-ray analyses. All-CO Fe(4)S(4) complexes 3 and 4 each display four-electron reduction processes in consecutive chemically reversible two-electron reduction events with relatively narrow potential spans in the cyclic voltammograms. Phosphine-substituted Fe(4)S(4) complexes 5 and 6 exhibit two consecutive two-electron reduction events, which are not fully reversible. The electrocatalytic properties of 3 and 4 for proton reduction were studied using a series of carboxylic acids of increasing strength (CH(3)COOH, CH(2)ClCOOH, CHCl(2)COOH, CCl(3)COOH, and CF(3)COOH). The mechanisms for electrochemical proton reduction to hydrogen catalyzed by complex 3 as a function of acid strength are discussed.