TY - JOUR

T1 - Metal Atom Clusters as Building Blocks for Multifunctional Proton-Conducting Materials

T2 - Theoretical and Experimental Characterization

AU - Daigre, Gilles

AU - Cuny, Jérôme

AU - Lemoine, Pierric

AU - Amela-Cortes, Maria

AU - Paofai, Serge

AU - Audebrand, Nathalie

AU - Le Gal La Salle, Annie

AU - Quarez, Eric

AU - Joubert, Olivier

AU - Naumov, Nikolay G.

AU - Cordier, Stéphane

PY - 2018/8/20

Y1 - 2018/8/20

N2 - The search for new multifunctional materials displaying proton-conducting properties is of paramount necessity for the development of electrochromic devices and supercapacitors as well as for energy conversion and storage. In the present study, proton conductivity is reported for the first time in three molybdenum cluster-based materials: (H)4[Mo6Br6S2(OH)6]-12H2O and (H)2[Mo6X8(OH)6]-12H2O (X = Cl, Br). We show that the self-assembling of the luminescent [Mo6L8 i(OH)6 a]2-/4- cluster units leads to both luminescence and proton conductivity (σ = 1.4 × 10-4 S·cm-1 in (H)2[Mo6Cl8(OH)6]-12H2O under wet conditions) in the three materials. The latter property results from the strong hydrogen-bond network that develops between the clusters and the water molecules and is magnified by the presence of protons that are statistically shared by apical hydroxyl groups between adjacent clusters. Their role in the proton conduction is highlighted at the molecular scale by ab initio molecular dynamics simulations that demonstrate that concerted proton transfers through the hydrogen-bond network are possible. Furthermore, thermogravimetric analysis also shows the ability of the compounds to accommodate more or less water molecules, which highlights that vehicular (or diffusion) transport probably occurs within the materials. An infrared fingerprint of the mobile protons is finally proposed based on both theoretical and experimental proofs. The present study relies on a synergic computational/experimental approach that can be extended to other proton-conducting materials. It thus paves the way to the design and understanding of new multifunctional proton-conducting materials displaying original and exciting properties.

AB - The search for new multifunctional materials displaying proton-conducting properties is of paramount necessity for the development of electrochromic devices and supercapacitors as well as for energy conversion and storage. In the present study, proton conductivity is reported for the first time in three molybdenum cluster-based materials: (H)4[Mo6Br6S2(OH)6]-12H2O and (H)2[Mo6X8(OH)6]-12H2O (X = Cl, Br). We show that the self-assembling of the luminescent [Mo6L8 i(OH)6 a]2-/4- cluster units leads to both luminescence and proton conductivity (σ = 1.4 × 10-4 S·cm-1 in (H)2[Mo6Cl8(OH)6]-12H2O under wet conditions) in the three materials. The latter property results from the strong hydrogen-bond network that develops between the clusters and the water molecules and is magnified by the presence of protons that are statistically shared by apical hydroxyl groups between adjacent clusters. Their role in the proton conduction is highlighted at the molecular scale by ab initio molecular dynamics simulations that demonstrate that concerted proton transfers through the hydrogen-bond network are possible. Furthermore, thermogravimetric analysis also shows the ability of the compounds to accommodate more or less water molecules, which highlights that vehicular (or diffusion) transport probably occurs within the materials. An infrared fingerprint of the mobile protons is finally proposed based on both theoretical and experimental proofs. The present study relies on a synergic computational/experimental approach that can be extended to other proton-conducting materials. It thus paves the way to the design and understanding of new multifunctional proton-conducting materials displaying original and exciting properties.

KW - MOLECULAR-DYNAMICS SIMULATION

KW - CHEVREL PHASES

KW - EXCESS PROTON

KW - DENSITY

KW - TRANSPORT

KW - IONS

KW - BR

KW - PHOTOLUMINESCENCE

KW - APPROXIMATION

KW - SOLVATION

UR - http://www.scopus.com/inward/record.url?scp=85051984970&partnerID=8YFLogxK

U2 - 10.1021/acs.inorgchem.8b00340

DO - 10.1021/acs.inorgchem.8b00340

M3 - Article

C2 - 30058331

AN - SCOPUS:85051984970

VL - 57

SP - 9814

EP - 9825

JO - Inorganic Chemistry

JF - Inorganic Chemistry

SN - 0020-1669

IS - 16

ER -