Bismuth oxychloride (BiOCl)-coated electroactive film was fabricated for the separation of cesium ions based on a potential-triggered method. The effects of applied potential, conductive carbon black (Super P Li), and different exposed facets on the adsorption of Cs+ ions were investigated. Experiments revealed that the adsorption efficiency gradually improved with increasing the applied potential to -0.7 V. The introduction of Super P Li improved the adsorption rate and increased the separation efficiency. The adsorption behavior followed pseudo-second-order kinetics. Additionally, the electroactive film showed adsorption selectivity for Cs+ in preference to Li+, Na+, and Rb+; seven consecutive adsorption-desorption experiments indicated that the electroactive film is sensitive to potential. The BiOCl nanosheets with exposed (001) facets exhibited a higher adsorption ratio for Cs+ removal than the counterpart with exposed (101) facets. It was also found that the separation performance of Cs+ ions was best in the neutral condition. It is expected that this BiOCl material can be used as a promising electroactive material for the removal of Cs+ ions from contaminated water in the future.