Shu-Zhong Zhan

A mononuclear copper electrocatalyst for both water reduction and oxidation

The oxidation and reduction of water is a key challenge in the production of chemical fuels from electricity. Although several catalysts have been developed for these reactions, substantial challenges remain towards the ultimate goal of an efficient, inexpensive and robust electrocatalyst. There is as yet no report on both water oxidation and reduction by the same catalyst. Reported here is a soluble copper-based catalyst, Na2[Cu(opba)] 1 (opba: o-phenylenebis(oxamato)) for water oxidation and reduction. Water oxidation occurs at an overpotential of 636 mV vs. SHE to give O2 with a turnover frequency (TOF) of ∼1.13 s−1. Electrochemical studies also indicate that 1 is a soluble molecular species, and that this is the most rapid homogeneous water-reduction catalyst, with a TOF of 1331.7 (pH 7.0) moles of hydrogen per mole of catalyst per hour in a pH 7.0 buffer at an overpotential of 788 mV vs. SHE. Sustained water reduction catalysis occurs at glassy carbon (GC) to give H2 over a 36 h electrolysis period with 96.5% Faradaic yield and no observable decomposition of the catalyst.

Synthesis and catalytic properties of an iron(III) complex supported by amine-bis(phenolate) ligand

The reaction of FeCl3 with 2-tetrahydrofuranylamino-N,N-bis(2-methylene-4-ethyl-6-tert-butylphenol), H2[O3N]BuEtTHF (H2L) affords a new iron(III) complex, [LFeCl] 1, whose structure has been determined by X-ray crystallography. Electrochemical studies show that 1 can electrocatalyze hydrogen evolution both from acetic acid with a turnover frequency (TOF) of 39.98 mol of hydrogen per mole of catalyst per hour at an overpotential of 941.6 mV (in DMF) and water with a TOF of 284.29 mol of hydrogen per mole of catalyst per hour at an overpotential of 896.8 mV (in buffer, pH 7.0). Sustained water reduction catalysis occurs at glassy carbon to give H2 over a 2 h electrolysis period with 95.81% faradaic yield and no observable decomposition of the catalyst.

Function of triazenido compound for electrocatalytic hydrogen production catalyzed by platinum complex

Abstract A new type of electrocatalyst based on a triazenido-platinum complex, Pt(PPh3)2(L)Cl (1), is prepared by the reaction of 1-[(2-methoxy) benzene]-3-[2-pyridine] triazene (HL) and Pt(PPh3)2Cl2 in the presence of triethylamine. Electrochemical studies indicate that HL, Pt(PPh3)2Cl2 and 1 can catalyze hydrogen evolution from acetic acid or a neutral buffer. To show triazenido ligand, HL, plays a role in determining the catalytic activities of the platinum complex, we systematically study the electrocatalytic activities of HL, Pt(PPh3)2Cl2 and Pt(PPh3)2(L)Cl and provide a possible catalytic mechanism for hydrogen generation catalyzed by 1.

Synthesis of an electro-catalyst based on a cobalt(II) complex with dimethylaminoethylamino-N,N-bis(2-methylene-4-tert-butyl-6-methylphenol)

Abstract A catalyst based on [LCo(H2O)] (1) is formed by the reaction of dimethylaminoethylamino-N,N-bis(2-methylene-4-tert-butyl-6-methyl)phenol (H2L) with CoBr2 for electrolytic proton or water reduction. 1 catalyzes hydrogen evolution, both from acetic acid with a turnover frequency (TOF) of 17.9 mol of hydrogen per mole of catalyst per hour at an overpotential of 792 mV (in DMF) and from water with a TOF of 260 mol of hydrogen per mole of catalyst per hour at an overpotential of 889 mV (in buffer, pH 7.0).

A molecular cobalt catalyst supported by an amine-bis(phenolate) ligand for both electrolytic and photolytic water reduction

A new molecular catalyst based on cobalt complex [L2Co2Cl2] 1 is prepared by the reaction of an amine-bis(phenolate) ligand (H2L) with CoCl2·6H2O for both electrolytic and photolytic water reduction. 1 can electrocatalyze hydrogen evolution from water with a turnover frequency (TOF) of 789.6 moles of hydrogen per mole of catalyst per hour at an overpotential of 837.6 mV (pH 7.0). 1 in a pH 6.0 aqueous solution under air, together with [Ru(bpy)3]Cl2 and ascorbic acid, in the presence of blue light (λmax = 469 nm) also produces hydrogen with a turnover number (TON) = 912 mol of H2 (mol of cat)−1.

Electrochemical-driven water reduction and oxidation catalyzed by an iron(III) complex supported by 2,3-bis(2-hydroxybenzylideneimino)-2,3-butenedinitrile

One molecular electrocatalyst for both water reduction and oxidation, based on an iron(III) complex [FeLCl(H2O)] 1, is formed by the reaction of anhydrous FeCl3 with a tetradentate ligand, 2,3-bis(2-hydroxybenzylideneimino)-2,3-butenedinitrile (H2L). Its structure has been determined by X-ray diffraction. 1 electro-catalyzes hydrogen evolution both from acetic acid and water, with a turnover frequency (TOF) of 10.25 and 808.46 moles of hydrogen per mole of catalyst per hour at an overpotential of 893 mV (DMF) and 837 mV (pH 7.0), respectively. Water oxidation occurs at an overpotential of 677 mV to give O2 with a TOF of ∼0.849 s−1.

Synthesis, characterization, luminescent, and catalytic performance of a dinuclear triazenido–silver complex

Abstract Our group has developed a series of molecular electrocatalysts for hydrogen generation based on triazenido–metal complexes (such as cobalt, copper, etc.). In this paper, we present the electrocatalytic performance of a new dinuclear silver complex, [Ag2(L)2], formed by reaction of the triazenido ligand, 1-[(2-carboxyethyl)benzene]-3-[benzimidazole]triazene (HL) with AgNO3. The electrocatalytic systems based on this silver complex can afford 91.23 and 473 moles of hydrogen per mole of catalyst per hour (mol H2/mol catalyst/h) from acetic acid at overpotential (OP) of 991.6 mV and an aqueous buffer at an OP of 837.6 mV, respectively. Electrochemical investigations show both the silver center and the triazenido ligand, HL, play important roles in determining the catalytic activities of the electrocatalytic system. Additionally, the triazenido ligand (HL) can serve as a fluorescent sensor for Ag+.