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Biochar materials have shown great potential for broad catalytic application. However, using these materials in the capacitive deionization technology (CDI) system for heavy metal removal still faces a significant challenge due to their low specific capacity and removal capability. Here, a comprehensive regulation on the interfacial/bulk electrochemistry of biochar by Zn doping is reported, which suggests a high renewable capacity (20 mg g -1 ) and outstanding selective capacitive removal ability (SCR) of Pb 2+ from leachate. The SCR efficiency of Pb 2+ is as high as 99% compared to K + (8%), Na + (13%), and Cd 2+ (37%). This work proves that the doped Zn on the biochar can combine with OH - generated by water splitting to form M─OH bonds, which is beneficial for improving the specific capacity. Significantly, the relationship between double-layer capacitance and pseudo-capacitance can also be optimized by regulating the content of Zn, leading to different removal abilities of heavy metals. Therefore, this work offers insights into charge-storage kinetics, which provide valuable guidelines for designing and optimizing the biochar electrode for broader environmental applications., (© 2024 Wiley‐VCH GmbH.)