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MoS2 Polymorphic Engineering Enhances Selectivity in the Electrochemical Reduction of Nitrogen to Ammonia Bryan Harry Rahmat Suryanto, Dabin Wang, Luis Miguel Azofra, Moussab Harb, Luigi Cavallo, Rouhollah Jalili, David Mitchell, Manjunath Chatti, and Douglas R. MacFarlane ACS Energy Lett., Just Accepted Manuscript • DOI: 10.1021/acsenergylett.8b02257 • Publication Date (Web): 28 Dec 2018 Downloaded from http://pubs.acs.org on January 1, 2019
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ACS Energy Letters
MoS2 Polymorphic Engineering Enhances Selectivity in the Electrochemical Reduction of Nitrogen to Ammonia
Bryan H. R. Suryanto,#,1* Dabin Wang,#,1 Luis Miguel Azofra,2* Moussab Harb,2 Luigi Cavallo,2 Rouhollah Jalili,3 David R. G. Mitchell,4 Manjunath Chatti,1 and Douglas R. MacFarlane1*
1
Australian Centre for Electrochemical Science,School of Chemistry, Monash University Clayton,
VIC 3800 (Australia). 2
KAUST Catalysis Centre (KCC),King Abdullah University of Science and Technology (KAUST)
Thuwal, 23955-6900 (Saudi Arabia). 3
4
School of Science, RMIT University, Melbourne, VIC 3001 (Australia) UOW Electron Microscopy Centre, University of Wollongong, Wollongong, NSW 2522 (Australia).
*Corresponding authors:
[email protected];
[email protected];
[email protected].
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ABSTRACT
The electrochemical N2 reduction reaction (NRR) offers a direct pathway to produce NH3 from renewable energy. However, aqueous NRR suffers from both low Faradaic efficiency (FE) and yield rate. The main reason is the more favoured H+ reduction to H2 in aqueous electrolytes. Here we demonstrate a highly-selective Ru/MoS2 NRR catalyst on which the MoS2 polymorphs can be controlled to suppress H+ reduction. A NRR FE as high as 17.6% and NH3 yield rate of 1.14×10-10 mol cm-2 s-1 is demonstrated at 50oC. Theoretical evidence supports a hypothesis that the high NRR activity originates from the synergistic interplay between the Ru clusters as N2 binding sites and nearby isolated S-vacancies on the 2H-MoS2 as centres for hydrogenation; this supports formation of NH3 at the Ru/2H-MoS2 interface. TOC GRAPHICS
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ACS Energy Letters
It is reported that the conventional Haber-Bosch process consumes approximately 2% of global energy supply and contributes ~1.5% of global greenhouse gas emissions.1 Renewable energy powered dinitrogen (N2) fixation technologies to synthesize ammonia (NH3) offers a core solution to the energy and environmental challenges caused by the conventional HaberBosch process.2 The electrochemical nitrogen reduction reaction (NRR) at ambient conditions offers a direct pathway for the conversion of renewable electricity into NH3 in a simple electrolytic cell.3 The required H+ can be sustainably supplied from a water oxidation process4. However, the NRR process is kinetically sluggish, involving the addition of 6e- and 6H+ and is electrochemically disfavored over the more facile, 2e- and 2H+ hydrogen evolution reaction (HER) in aqueous solution.3, 5 The highly disruptive HER largely explains why most of the recently reported metal based electrocatalysts such as Ru,6 Pt,7 Au,8 Rh,9 Fe,10-11 Mo,12 Pd,13 Cr,14 and N-doped carbon based materials15-16, often suffer from both low NRR Faradaic efficiency of
