title: Coordination polymer structure and revisited hydrogen evolution catalytic mechanism for amorphous molybdenum sulfide.
abstract: Molybdenum sulfides are very attractive noble-metal-free electrocatalysts for the hydrogen evolution reaction (HER) from water. The atomic structure and identity of the catalytically active sites have been well established for crystalline molybdenum disulfide (c-MoS2) but not for amorphous molybdenum sulfide (a-MoSx), which exhibits significantly higher HER activity compared to its crystalline counterpart. Here we show that HER-active a-MoSx, prepared either as nanoparticles or as films, is a molecular-based coordination polymer consisting of discrete [Mo3S13](2-) building blocks. Of the three terminal disulfide (S2(2-)) ligands within these clusters, two are shared to form the polymer chain. The third one remains free and generates molybdenum hydride moieties as the active site under H2 evolution conditions. Such a molecular structure therefore provides a basis for revisiting the mechanism of a-MoSx catalytic activity, as well as explaining some of its special properties such as reductive activation and corrosion. Our findings open up new avenues for the rational optimization of this HER electrocatalyst as an alternative to platinum.
authors.affiliation: Energy Research Institute, Nanyang Technological University, 50 Nanyang Drive, Singapore 637553, Singapore.|Solar Fuel Laboratory, School of Materials Science &Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.|Department of Advanced Materials Science and Nanotechnology, University of Science and Technology of Hanoi, 18 Hoang Quoc Viet, Hanoi, Vietnam.
authors.forename: Phong D
authors.initials: PD
authors.lastname: Tran
authors.affiliation: Electronics-Inspired Interdisplinary Research Institute, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku, Toyohashi 441-8580, Japan.
authors.forename: Thu V
authors.initials: TV
authors.lastname: Tran
authors.affiliation: Institut des Sciences Moléculaires de Marseille, Aix Marseille Université, CNRS, Centrale Marseille, ISM2 UMR 7313, 13397 Marseille, France.
authors.forename: Maylis
authors.initials: M
authors.lastname: Orio
authors.affiliation: Laboratoire de Chimie et Biologie des Métaux, Univ. Grenoble Alpes, CNRS, CEA, 17 rue des Martyrs, 38054 Grenoble, France.
authors.forename: Stephane
authors.initials: S
authors.lastname: Torelli
authors.affiliation: Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aobaku, Sendai 980-8577, Japan.
authors.forename: Quang Duc
authors.initials: QD
authors.lastname: Truong
authors.affiliation: Field Solution Division, JEOL Ltd, 1156 Nakagami, Akishima, Tokyo 196-0022, Japan.
authors.forename: Keiichiro
authors.initials: K
authors.lastname: Nayuki
authors.affiliation: Field Solution Division, JEOL Ltd, 1156 Nakagami, Akishima, Tokyo 196-0022, Japan.
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Sasaki
authors.affiliation: Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 3 Research Link, Singapore 117602, Singapore.
authors.forename: Sing Yang
authors.initials: SY
authors.lastname: Chiam
authors.affiliation: Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 3 Research Link, Singapore 117602, Singapore.
authors.forename: Ren
authors.initials: R
authors.lastname: Yi
authors.affiliation: Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aobaku, Sendai 980-8577, Japan.
authors.forename: Itaru
authors.initials: I
authors.lastname: Honma
authors.affiliation: Solar Fuel Laboratory, School of Materials Science &Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.|Department of Life Sciences, Imperial College London, London SW7 2AZ, UK.
authors.forename: James
authors.initials: J
authors.lastname: Barber
authors.affiliation: Laboratoire de Chimie et Biologie des Métaux, Univ. Grenoble Alpes, CNRS, CEA, 17 rue des Martyrs, 38054 Grenoble, France.
authors.forename: Vincent
authors.initials: V
authors.lastname: Artero