MoS2/Al2O3　catalysts　were　prepared　by　a　simultaneous　impregnation　method　with　citric　acid　as　chelating　agent　in　order　to　investigate　the　effect　of　high　pressure　sulfidation　on　the　morphology　and　reactivity　of　MoS2　slabs　by　infrared　spectroscopy　of　CO　adsorption　(IR/CO),　transmission　electron　microscopy,　thiophene　hydrodesulfurization　(HDS)　and　2,6-dimethylaniline　hydrodenitrogenation　(HDN)　reactions.　It　is　found　that　the　MoS2　slabs　are　more　truncated　when　sulfided　at　higher　pressure,　exposing　larger　S-edge/M-edge　ratio.　The　thiophene　HDS　activity　of　MoS2/Al2O3　catalysts　was　significantly　improved　by　high　pressure　sulfidation.　The　MoS2　edges　formed　after　high　pressure　sulfidation　are　very　stable　toward　H2-treatment,　while　the　same　H2-treatment　can　create　sulfur　vacancies　on　both　M-edge　and　S-edge　of　the　0.1　MPa　sulfided　MoS2　slabs.　Meanwhile,　parallel　between　the　IR/CO　results　and　HDN　test　suggests　that　the　S-edge　favors　the　C-N　bond　scission　whereas　the　M-edge　benefits　the　hydrogenation　in　HDN　reaction.　©　2016　Elsevier　Inc.　All　rights　reserved.