The suppression of proton reduction can enable new types of chemoselective (hetero)arene reduction by running reactions deliberately under acidic conditions (Figure ). This is challenging for DC electrolysis since proton reduction is more pronounced under acidic conditions, and not advisable for chemical arene reduction owing to dangerously aggressive reactions of alkali metals with acids. As a proof of concept for this interesting possibility, standard rAP reduction of 48 furnished debrominated dihydropyrolidine 49 in 40% yield via dissociative electron-transfer, common phenomenon during single-electron reduction of halogenated arenes. In striking contrast, running the same reaction in the presence of 10 equiv of AcOH furnished dihydropyrrolidine 50 in 65% yield, maintaining the useful C-Br bond. As expected, the corresponding DC electrolysis under identical conditions required a much longer reaction time (6 h, 45 "equiv" of electrons) due to the competing proton reduction, and only delivered 11% of 50 along with 17% recovered 48. Another dramatic benefit for suppressing proton reduction was found during scale-up efforts (Figure ). Thus, optimized conditions for small scale could be modified to realize the reaction under more process-friendly conditions. Key modifications included replacing the sacrificial electron-donor DMS to i Pr2NH (buffered with pivalic acid) as well as switching solvents from THF/EtOH to more conductive MeOH. In addition, RVC electrodes were replaced with graphite electrodes due to unsatisfactory mechanical properties of RVC on scale. With these modifications, rAP-based conditions successfully afforded the product 2 in 84% isolated yield on 50 mmol scale, whereas DC electrolysis resulted in full recovery of 1 under identical reaction conditions. Again, a large volume of gas evolution was observed during DC electrolysis, rendering the arene reduction unfavorable under such simple conditions.