Study on the construction of nitrogen-doped porous biochar via dual template synergistic regulation and its non-radical dominated PMS activation mechanism

Abstract

A high-efficiency material with uniform pores (2.1–2.4 nm) was successfully prepared via a "doping-volatilization" dual-template strategy using ZnCl₂ and urea as dual-template reagents for walnut shell biochar modification. The influence of this material on peroxymonosulfate (PMS) activation was systematically investigated. Experimental results demonstrated that uniform pores played a critical role in regulating morphology and enhancing mass transfer rates. Under identical experimental conditions (i.e., catalyst dosage: 40 mg; PMS concentration: 200 mg·L⁻¹), the catalyst prepared via the dual-template method exhibited significantly higher catalytic activity compared to those derived from single-template methods (NBC and ZBC). Specifically, it demonstrated a 6.5-fold enhancement in activity relative to NBC and a 1.8-fold improvement over ZBC. Significant performance differences were observed among catalysts in PMS activation for tetracycline (TC) degradation, where non-radical pathways (e.g., ¹O₂) dominated the reaction, and pore/defect structures served as primary active sites. This study further revealed that the dual-template synergy originated from the coupling of ZnCl₂ volatilization-induced pore formation and urea-mediated nitrogen doping. During pyrolysis, urea acted as an exogenous nitrogen source to stabilize nitrogen content whereas ZnCl₂ volatilized but removed endogenous nitrogen from biomass. This work provides insights into the structure-property relationships of carbon materials and advances.