title: Valence and oxide impurities in MoS2and WS2dramatically change their electrocatalytic activity towards proton reduction.
abstract: Layered molybdenum disulfide (MoS2) and tungsten disulfide (WS2) have received renewed interest in recent years as they are catalytic towards the hydrogen evolution reaction (HER) and they are touted as future replacements of platinum in electrolyzers. There is a significant discrepancy in the found onset potentials of MoS2and WS2towards the hydrogen evolution reaction. Here we show that the presence of valence sulfide impurities, such as MoS3and WS3, and their oxide counterparts, such as MoO2, MoO3and WO2, WO3can contribute to the catalytic activity towards hydronium reduction to hydrogen of MoS2and WS2. Therefore, it is highly possible that the differences in the reported onset potentials and thus catalytic activities of the MoS2and WS2are due to the presence of catalytic impurities.
authors.affiliation: Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore. pumera.research@gmail.com.
authors.forename: Naziah
authors.initials: N
authors.lastname: Mohamad Latiff
authors.affiliation: Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore. pumera.research@gmail.com.
authors.forename: Lu
authors.initials: L
authors.lastname: Wang
authors.affiliation: Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore. pumera.research@gmail.com.
authors.forename: Carmen C
authors.initials: CC
authors.lastname: Mayorga-Martinez
authors.affiliation: Department of Inorganic Chemistry, University of Chemistry and Technology Prague, Technicka 5, 166 28, Prague 6, Czech Republic.
authors.forename: Zdeněk
authors.initials: Z
authors.lastname: Sofer
authors.affiliation: Department of Chemical Engineering and Biotechnology, University of Cambridge, UK.
authors.forename: Adrian C
authors.initials: AC
authors.lastname: Fisher
authors.affiliation: Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore. pumera.research@gmail.com.
authors.forename: Martin
authors.initials: M
authors.lastname: Pumera