Single-Ni-atom catalyzes aqueous phase electrochemical reductive dechlorination reaction

[Display omitted] •Atomically dispersed Ni (A-Ni-NG) electrocatalyst was developed for dechlorination.•A-Ni-NG exhibited highest activities to dechlorination of chloroacetic acids (CAAs).•High activity of A-Ni-NG stems from its specific interactions with intermediate.•The Cl atoms in CAAs are eliminated sequentially through a direct mechanism.•Electron transfer step occurs in a stepwise manner with breaking C–Cl bond. Electrochemical dechlorination offers a promising strategy to convert refractory chlorinated organic pollutants (COPs) to biodegradable chlorine-free organics under mild conditions. In this work, we report atomically dispersed nickel anchored on nitrogenated graphene (A-Ni-NG) as an efficient dechlorination catalyst, and study its underlying dechlorination pathway and catalytic mechanism, using chloroacetic acids (CAAs) as the model COPs. The A-Ni-NG exhibits higher catalytic activity than state-of-the-art Pd and Ag catalysts. Using A-Ni-NG as a catalyst, complete dechlorination of CAAs to acetic acid can be achieved at pH 3, 7 and 11. The Cl atoms in CAAs are eliminated sequentially through a direct dechlorination mechanism. The exceptional electrocatalytic activity of A-Ni-NG stems from the specific interactions between A-Ni-NG and the substrate as well as the primary intermediate generated from the first electron transfer (ET) step, and the ET step occurs in a stepwise manner with breaking CCl bond.