This　work　aimed　at　investigating　electrocatalytic　hydrodechlorination　(ECH)　mechanisms　of　chlorophenols　(CPs)　on　a　Pd-modified　cathode.　Experiments　on　the　ECH　of　2,4-dichlorophenol　were　conducted　under　extreme　test　conditions,　i.e.,　with　various　buffer　solutions　and　several　sodium　salt　solutions　as　supporting　electrolytes.　Buffer　solutions　promote　dechlorination　due　to　their　property　of　retarding　the　alkalinity　of　a　solution.　ECH　was　found　to　be　significantly　inhibited　by　sulfite.　Experimental　results　showed　that　sulfite　poisoning　on　Pd　catalysts　was　reversible.　Protonation　may　account,　at　least　in　part,　for　the　observed　high　pH　dependency　of　ECH,　which　proceeded　rapidly,　with　lower　apparent　activation　energy　(Ea)　in　the　acidic　electrolyte.　In　addition,　pH　influenced　the　selectivity　of　dechlorination　of　CPs.　It　was　inferred　that　the　ECH　of　CPs　on　the　Pd-modified　electrode　was　a　preactivated　electrocatalytic　reaction.