Developing highly active and stable ethanol oxidation electrocatalysts is crucial for direct ethanol fuel cells. Herein, platinum/molybdenum disulfide nanoflower (Pt/MoS2) nano-composite is synthesized through a facile method and is first applied as catalyst for ethanol oxidation reaction. In situ electrochemical nuclear magnetic resonance is carried out to investigate the electrocatalytic activity of Pt/MoS2 and the detailed mechanism of ethanol oxidation reaction. Experimental results indicate that in situ electrochemical nuclear magnetic resonance possesses great advantages for real-time investigation of ethanol oxidation reaction, and Pt/MoS2 is found to exhibit better electrocatalytic performances in terms of higher current density, better stability, and stronger anti-poisoning activity compared to commercial Pt/C and pure Pt catalysts in acid electrolyte, suggesting its potential for application in direct ethanol fuel cells. Density functional theory calculations indicate that MoS2-supported Pt atom has a smaller energy barrier for the dissociation of ethanol compared to those of Pt and C-supported Pt atom, leading to the enhancement of catalytic activity. This work reveals the importance of the supporting materials for high performance direct ethanol fuel cells catalysts. (C) 2019 Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC.