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Monday - 14/03/2016 22:13

Revealing structure and mechanistic function of amorphous molybdenum sulfide, an attractive alternative to platinum catalyst for the Hydrogen Evolution Reaction Solar water splitting represents a huge challenge and a great opportunity for harvesting abundant but intermittent solar energy into chemical energy stored within H2 molecules. To this end, several technical challenges are remained, including identification of viable electrocatalyst for the Hydrogen Evolution Reaction (HER). Amorphous molybdenum sulfide (a-MoSx) was identified as an attractive candidate to replace platinum, the ever best HER catalyst but being precious, less abundant noble metal. However, structure of this a-MoSx remained unclear which was a huge gap for understanding its mechanistic function and subsequently searching for means to improve its catalytic performance. This gap is now filled, thanks to recent work conducted by Dr. Phong D. Tran research group at Department of Advanced Materials Science and Nanotechnology, University of Science and Technology of Hanoi (USTH) in collaboration with researchers in France, Japan and Singapore. This breakthrough work is published in the prestigious journal Nature Materials (IF 36.5). Employing an arsenal of chemical, electrochemical and spectroscopic analysis, type STEM, Resonance Raman, XPS, international research team led by Dr. Phong D. Tran evidenced that so-called amorphous molybdenum sulfide is actually a coordination polymer with [Mo3S13]2 discrete clusters as building block units. These [Mo3S13]2 clusters share two of their three terminal disulfide (SS)2 groups to build up the polymeric chain while the third disulfide (SS)2 terminal group is remained free (figure 1). Within the polymeric chain, some defect sites being unsaturated coordination MoIV/V type Mo=O are present. However, these structural defects were found to be easily converted into H2evolving catalytic sites, being MoIV with vacant sites presented on MoIV centre, just via an electrochemical reduction process. Furthermore, MoIV H2evolving catalytic sites are also produced by reductive removal of terminal disulfide ligands. A series of electrochemical and spectroscopic analyses were conducted to describe in details the activation and mechanistic function of the a-MoSx catalyst. DFT calculation further supported the mechanism proposed. Phong -Nature Figure 1. Structure of a-MoSx being identified to be a coordination polymer with [Mo3S13]2 discrete clusters as building block units. Under catalytic H2evolving conditions, the free terminal disulfides are removed creating MoIV center with vacant sites. H2 evolution on this centre was found to run through a MoVH intermediate. The identification of structure and mechanistic function of a-MoSx catalyst paves new ways for further improving its catalytic performance. This important finding also provides very useful instruction for designing novel viable catalysts based on sulfides of transition metals. Currently, research group led by Dr. Phong D. Tran at Department of Advanced Materials Science and Nanotechnology, USTH focus on designing novel catalysts based on these findings as well as implementing these catalysts within photoelectrodes, photocatalysts or devices for solar H2 generation application. These researches are funded by USTH, NAFOSTED (project was accepted for funding for 2016-2018 period), USTH FR consortium and French Embassy in Hanoi. Reference Phong D. Tran, Thu V. Tran, Maylis Orio, Stephane Torelli, Quang Duc Truong, Keiichiro Nayuki, Yoshikazu Sasaki, Sing Yang Chiam, Ren Yi, Itaru Honma, James Barber, Vincent Artero* Coordination polymer structure and revisited hydrogen evolution catalytic mechanism for amorphous molybdenum sulfide Nature Materials. 14 March 2016 DOI: 10.1038/NMAT4588 Contact: Dr. Phong D. Tran Department of Advanced Materials Science and Nanotechnology University of Science and Technology of Hanoi Email: tran-dinh.phong@usth.edu.vn SMS: +84 (0)96 46 021 46 Dr. Phong D. Tran obtained his Bachelor of Science (2003) at Vietnam National University in Hanoi, and PhD degree (2007) at University of Paris Sud (Paris 11), Orsay, France. He worked for three years (2008-2010) as postdoctoral research associate at CNRS and CEA France. From February 2011 to June 2015, he worked as senior research fellow at Solar Fuels Laboratory, Nanyang Technological University, Singapore. Since July 2015, he joined Department of Advanced Materials Science and Nanotechnology, University of Science and Technology of Hanoi, as a lecturer and principal investigator. His current research interests focus on designing advanced functional nanomaterials for energy conversion and environment applications. He has published 37 papers in international peer-reviewed journals including papers in Science, Nature Materials, Natural Chemistry, Angewandte Chimie, Energ  Environmental Sciences. His current citation index is over 1700 and H index is 18. To download the MS Word version, please click herePress release_English_TRAN DINH PHONG