Hydrogen peroxide as a key intermediate for hydroxyl radical generation during catalytic ozonation of biochar: Mechanistic insights into the evolution and contribution of radicals

•Biochar had much greater reactivity than common ozone catalytic materials.•The ozone utilization efficiency and Rct value were greatly increased.•Free hydroxyl radicals were the sole species for degradation of target pollutants.•Hydrogen peroxide was generated as a key intermediate for hydroxyl radical formation.•Pollutant adsorption was not a prerequisite for efficient degradation.