Efficient electro-demulsification of O/W emulsions and simultaneous oil removal enabled by a multiscale porous biocarbon electrode

•Carbonized biomass as a self-standing electrode promotes electro-demulsification.•Carbonized biomass as self-standing electrode also promotes oil removal.•Electrode capacity reached 1180 mg g−1 (97.97 %) toluene removal at 5.0 V for 3.4 h.•The electric field compressed and ruptured emulsion droplets in porous electrodes.•Electrostatic adsorption caused small molecule adherence to graphitic pore walls.