Metal-modified nitrogen self-doped biochar as an electrode plate for electrocatalytic removal of methylene blue

Iron-modified nitrogen-self-doped biochar was synthesized from cyanobacteria as electrode materials for the electrocatalytic degradation of methylene blue (MB). Cyanobacteria-based biochar was prepared via pyrolysis at 300-700 °C, and iron loading was performed to obtain composite electrodes (BEP₃₀₀-BEP₇₀₀), which were characterized by multiple analytical techniques. Systematic investigation of key parameters affecting MB degradation showed that acid-treated FeBEP₅₀₀ (pyrolyzed at 500 °C) achieved a maximum degradation efficiency of 99.65% within 45 min under optimal conditions (initial pH = 3, catalyst dosage = 0.1 g, MB concentration = 100 mg/L, applied voltage = 9 V). Quenching experiments revealed that cyanobacteria provided carbon for the biochar framework and nitrogen to facilitate the Fe²⁺/Fe³⁺ redox cycle in Fenton-like reactions. FeBEP₅₀₀ exhibited excellent recyclability via magnetic separation, retaining over 93% MB removal efficiency after five cycles and calcination regeneration, thus showing great potential for the electrocatalytic removal of aqueous organic pollutant.