Structure-property relationship and mechanism of peroxymonosulfate activation by nitrogen-doped biochar for organic contaminant oxidation

Nitrogen doping has been found to effectively promote the catalytic activation of peroxymonosulfate (PMS) by biochar in the application of organic contaminant degradation. However, the dominant active sites of nitrogendoped biochar (NBC) and the exact catalytic oxidation mechanism in behind remain ambiguous. Herein, a series of NBC samples were prepared as PMS activators to facilitate oxidative degradation of 2,4-dichlorophenol, and the functions of nitrogen bond configurations, oxygen-containing groups, and structural defects were systematically investigated during catalytic oxidation. The oxidation rate constant shows a great positive linearity with the relative amount of ketonic (C--O) groups and the defect level of biochar, which indicates that the C--O groups and structural defects play a major role in PMS activation, acting as dominant active sites to promote the catalytic oxidation of NBC by generating O2.- and 1O2. This study offers new insight into the significant role of NBC during PMS activation and further provides theoretical support to guide the rational design of nitrogen doping strategies.