Facile Pyrolysis Treatment for the Synthesis of Single-Atom Mn Catalysts Derived from a Hyperaccumulator

Abstract

Advanced oxidation processes (AOPs) have revealed wide prospects in the application of the degradation of organic contaminants in ground water and soil. High-performance, environmentally friendly, and low-cost single-atom catalysts (SACs) are promising approaches to active persulfate in AOPs. However, the practical application of SACs is restricted by high preparation costs and tedious procedures. Herein, a manganese (Mn) hyperaccumulator, Phytolacca americana, was successfully exploited as a precursor to synthesize a novel Mn SAC (SPBC-700N) via a one-step pyrolysis method. In SPBC-700N, Mn atoms are dispersed atomically upon the carbon matrix and coordinate with four N atoms to form Mn–N4 active sites, which exhibits an extraordinary catalytic activity for peroxymonosulfate (PMS) activation. A large number of reactive oxygen species are formed during the reaction, and over 90% of the antibiotic (chloroquine phosphate/CQP) could be removed within 30 min. The superior catalytic performance of the Mn SAC/PMS system for CQP degradation is ascribed to the synergistic effect of the maximized utilization of Mn atoms and the neighboring pyrrolic N sites, as identified by X-ray absorption fine structure spectroscopy and density function theory calculations. This work not only provides a green and low-cost strategy for synthesizing SACs but also gives an atomic-level insight into the catalytic activity of the Mn–N4 sites for PMS activation.

Insights into O2 Activation via MnIIIOOH Species on Mn-Rich Biochar

“…Figure a shows that the diffraction peaks of Mn-BC are assigned to KCl at 2θ = 28.3, 40.5, 50.1, and 30.9° (JCPDF 41-1476), CaC 2 O 4 at 2θ = 14.9 and 30.0° (JCPDF 20-0231), and MnC 2 O 4 at 2θ = 24.4, 36.0, and 38.2° (JCPDF 25-0544). MnC 2 O 4 is produced by the complexation of Mn with oxalic acid secreted by plant roots, , which are consistent with the reported hyperaccumulator-derived biochar. , There are weak diffraction peaks at 2θ = 26.7°, corresponding to the characteristic diffraction peaks of MnO 2 . It has been demonstrated that MnO 2 originates from the decomposition of MnC 2 O 4 by pyrolysis at 300 °C .…”

“…Biochar materials have been widely used in soil remediation. , Plant-derived biochar is inevitably enriched with crustal elements, especially in severe heavy metal pollution. , For example, Ni, Pb, and Cd loading in biochar derived from hyperaccumulators are as high as 5 mg/g, , and Mn and Zn contents are more than 60 mg/g . When heavy metals are in excess, they are bound to plant metal proteins and immobilized by heteroatoms like N, S, and P, creating stable and active monatomic catalysts. , Because of this, metal-rich biochars (M-BC) have received much attention for their potential in pollution control. M-BC can be used in biochar-based advanced oxidation processes without the need for external metal loading.…”

“…7 When heavy metals are in excess, they are bound to plant metal proteins and immobilized by heteroatoms like N, S, and P, creating stable and active monatomic catalysts. 8,9 Because of this, metal-rich biochars (M-BC) have received much attention for their potential in pollution control. M-BC can be used in biochar-based advanced oxidation processes without the need for external metal loading.…”

Nanostructured single-atom catalysts derived from natural building blocks

“…For instance, by employing Phytolacca americana , an Mn hyperaccumulator, as the precursor, a novel Mn SAC featuring an Mn–N 4 structure was synthesized successfully through direct carbonization. 56 However, the majority of biomass mainly consists of C, O, and hydrogen (H), with typically low levels of intrinsic metal elements, which can potentially constrain the overall catalytic performance of the resultant CS-SACs.…”

Ground-Breaking and Safe Recycling of Hazardous Hyperaccumulators

“…Hyperaccumulators, a group of plants for cost-effective environmental remediation, are annually produced in a large scale. − Notably, the abundant carbon sources in harvested plants could be reutilized to produce valuable carbon materials. − However, exposure of these carbon materials will lead to migration of endogenous metals, which may induce secondary pollution via environmental release . Hence, an efficient and eco-friendly treatment is required to synchronously decontaminate and upgrade these hazardous hyperaccumulators.…”