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• A Pd/Ni(OH) 2 -NF catalyst was prepared for deuteration (hydrogenation) reaction of aryl alkynes. • A room-temperature one-pot two-step transformation of 4-ethynylaniline to deuterated 4-vinylanilin was constructed with a conversion rate of up to 96%, a selectivity of 98%, and a deuterium ratio of 99% using D 2 O as a deuterium source. • The rapid kinetics of D 2 O electrolysis was proved to contribute to the semi-deuteration of aryl alkynes by electrochemical analysis. • A wide range of substrates and easy access to hydrogenated alkenes highlight the promising applications. The preparation of deuterated alkenes via electrochemistry from a readily available deuterated source has the advantages of mild reaction conditions, sustainability, and cost-effectiveness. Hydrogen isotopic exchange is a simple method to introduce deuterium atoms into molecules without prior functionalization. However, this process typically requires complex ligand catalysts, costly sources of deuterium, and strong bases and acids to activate the robust C-H bonds. The deuterated incorporation sites and their corresponding numbers are difficult to control. In this study, an in-situ electrochemical deuteration system is reported that is based on a Pd/Ni(OH) 2 nanoflake catalyst grown on a commercial nickel foam conductive substrate was used as the cathodic working electrode. A room-temperature, one-pot, two-step transformation of 4-ethynylaniline to deuterated 4-vinylanilin was achieved with a conversion rate of up to 96%, selectivity of 98%, and a deuterium ratio of 99% using D 2 O as the deuterium source. The interaction between Pd and Ni(OH) 2 -NF promoted the rapid cleavage of D 2 O during the semi-deuteration of aryl alkynes. The key deuterium and carbon radical intermediates were confirmed using electron paramagnetic resonance spectroscopy. A wide range of substrates and easy access to hydrogenated alkenes highlight the promising applications. [ABSTRACT FROM AUTHOR]