Electrocatalytic hydrodechlorination of 2,4-dichlorophenol over palladium nanoparticles: The critical role of hydroxyl group deprotonation

[Display omitted] •CP inclines to deprotonate at its hydroxyl, and the ionized CPs dominate the species of reactants.•Hydroxyl deprotonation leads the detrimental effects on EHDC efficiency/degree.•Hydroxyl deprotonation leads to the bond cleavage superiority of 4-C-Cl to 2-C-Cl.•A lower pH and a more positive potential enable to alleviate the detrimental effect. Chlorinated phenol tends to deprotonate at its hydroxyl group in water, and the ionized CPs dominate the species of reactants in electrocatalytic hydrodechlorination reaction (EHDC). Here we determined the high tendency of the hydroxyl group deprotonation on 2,4-dichlorophenol (2,4-DCP) was highly detrimental to the EHDC reaction on Pd catalysts. This adverse effect arised from the repulsive force generated between the cathode and the ionized 2,4-DCP, which repelled them away from the cathode surface. Notably, the hydroxyl group deprotonation replaced the side hydrogen evolution as primary cause of the poor EHDC performance at low potentials (