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Laboratoire d'Electrochimie Moleculaire, LEM, Paris

UMR CNRS - Université Paris Diderot - Paris France

Master Frontiers in Chemistry | UFR de Chimie - Université Paris Diderot - Paris 7 CNRS - Institut de chimie Université de Paris Master Chimie Sorbonne Paris Cité UFR de Chimie - Université Paris Diderot - Paris 7 CNRS - Institut de chimie
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Université Paris Diderot
Université de Paris CNRS, Centre National de la Recherche Scientifique

Le LEM - Publications: Abstracts

Publication 764

ACS. Catal., 5 (1), 356-364, 2015

Dual homogeneous and heterogeneous pathways in photo- and electrocatalytic hydrogen evolution with nickel(II) catalysts bearing tetradentate macrocyclic ligands

Lingjing Chen, Gui Chen, Chi-Fai Leung, Shek-Man Yiu, Chi-Chiu Ko, Elodie Anxolabéhère-Mallart, Marc Robert, and Tai-Chu Lau

Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong SAR, China
Université Paris Diderot, Sorbonne Paris Cité, Laboratoire d’Electrochimie Moléculaire, Unité Mixte de Recherche Université−CNRS no. 7591, Bâtiment Lavoisier, 15 rue Jean de Baïf, 75205 Paris Cedex 13, France

A series of nickel(II) complexes bearing tetradentate macrocyclic N4, N3S, and N3P ligands were synthesized, and their photocatalytic activity toward proton reduction has been investigated by using [Ir(dF(CF3)ppy)2(dmbpy)]PF6 (dF(CF3)ppy = 2-(2,4-difluorophenyl)-5-trifluoromethylpyridine and dmbpy = 4,4'-dimethyl-2,2'-dipyridyl) as the photosensitizer and triethylamine (TEA) as the sacrificial reductant. The complex [Ni(L4)]2+ (L4 = 2,12-dimethyl-7-phenyl-3,11,17-triaza-7-phospha-bicyclo[11,3,1]heptadeca-1(17),13,15-triene), which bears a phosphorus donor atom, shows the highest efficiency with TON up to 5000 under optimized conditions, while the tetraaza macrocyclic nickel complexes [Ni(L1)]2+ and [Ni(L2)]2+ (L1 = 2,12-dimethyl-3,7,11,17-tetra-azabicyclo[11.3.l]heptadeca-1(17),2,11,13,15-pentaene; L2 = 2,12-dimethyl-3,7,11,17-tetra-azabicyclo[11.3.l]heptadeca-1(17),13,15-triene) show lower photocatalytic activities. Transient UV–vis absorption and spectroelectrochemical experiments show that Ni(II) is reduced to Ni(I) under photocatalytic conditions. However, dynamic light scattering and mercury poisoning experiments suggest that the Ni(I) is further reduced to Ni(0) nanoparticles which are the real catalysts for H2 production. Electrocatalytic proton reduction by [Ni(L4)]2+ has also been investigated. In this case, the electrochemical behavior is consistent with a homogeneous pathway, and no Ni nanoparticles were observed on the electrode surface during the first few hours of electrolysis. However, on prolonged electrolysis for >17 h, nickel-based nanoparticles were observed on the electrode surface, which are active catalysts for H2 production.

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