Surfactant-exfoliated 2D molybdenum disulphide (2D-MoS2): the role of surfactant upon the hydrogen evolution reactionElectronic supplementary information (ESI) available: The characterisation of the 2D-MoS2 and 2D-MoS2-SC as well as details of the calculations of the turn over frequency and more a detailed experimental method section is presented. See DOI: 10.1039/c7ra05085b

Surfactant (sodium cholate, SC) mediated liquid (aqueous) phase exfoliation is a common approach to fabricate 2D molybdenum disulphide (2D-MoS 2 -SC) nanosheets since it is a facile methodology producing defect free flakes with nanometer lateral sizes. The electrocatalytic behaviour of 2D-MoS 2 -SC towards the Hydrogen Evolution Reaction (HER) is benchmarked within acidic media and found to exhibit inferior HER activity to an equivalent mass of pristine 2D-MoS 2 (2D-MoS 2 produced without a surfactant), with HER onset potentials, current densities and Tafel values of −0.61 V ( vs. SCE), −2.19 mA cm −2 , 141 mV dec −1 and −0.42 V ( vs. SCE), −4.96 mA cm −2 , 94 mV dec −1 respectively. This work demonstrates that sodium cholate has a detrimental effect upon the HER activity of 2D-MoS 2 . Future studies that utilise 2D materials, fabricated via liquid surfactant exfoliation, should consider the role of the surfactant in the observed electrochemical responses and perform the necessary control experiments. The surfactant (sodium cholate) when used in the liquid exfoliation of 2D-MoS 2 has a detrimental effect upon its electrocatalytic activity compared to pristine 2D-MoS 2 (produced without a surfactant).