<p>Deuterated organic compounds have gained significant attention due to their diverse applications, including reaction mechanism studies, probes for metabolism and pharmacokinetics, and raw materials for labeled compounds and polymers. Conventional reductive deuteration methods are limited by the high cost of deuterium sources (e.g., D₂ gas) and challenges in product separation and D₂O recycling. Electrochemical deuteration using D₂O is promising, but existing methods still suffer from low Faradaic efficiency (FE) and high separation costs. Herein, we report a deuterium ion diffusion-based all-solid electrolyser, featuring a RuO₂ anode for D⁺ generation from pure D₂O and a Pd/nitrogen-doped carbon-based liquid diffusion cathode (Pd^δ+/NC LDC) with tunable electron deficiencies Pd^δ+/NC to enhance selective deuteration. This system achieves over 99% selectivity for deuterated benzyl alcohol with a FE of 72%, and demonstrates broad applicability for the deuteration of aldehydes, ketones, imines, and alkenes with high FE and selectivity. Moreover, the Pd^δ+/NC-based electrolyser can achieve ten-gram-scale production of deuterated benzyl alcohol over 500 hours, showcasing its potential for high-throughput, solvent-free deuteration reactions in practical applications.</p>