Nano boron carbide effectively boost Fenton-like performance of hematite mediated systems: Roles of hematite exposed...

The inherent properties of exposed facets of iron minerals played key roles in heterogeneous reactions at the mineral interface, and the addition of co-catalysts has been elucidated to further enhance the reactions for contaminants degradation. Here, synergistic Fenton-like catalytic reactivity of different hematite dominant exposed facets ({001}, {012}, {100}, and {113}) with nano boron carbide (B₄C) was revealed. In 5 h, as compared with the cumulative •OH in the B₄C/H₂O₂ system (96.9 μM), while that in the {001}/B₄C/H₂O₂ system was decreased by 19.6%, those in the {012}/B₄C/H₂O₂, {100}/B₄C/H₂O₂, and {113}/B₄C/H₂O₂ systems were increased by 53.8%, 75.9%, and 84.0%, respectively. Significantly, {113}/B₄C/H₂O₂ system exhibited strong capability for degradation of a broad spectrum of organic pollutants, including typical phenol, endocrine disruptor (bisphenol A), antibiotic (sulfanilamide), dyes (Rhodamine B and methylene blue), and pesticide (atrazine). During the Fenton-like reactions, higher synergy factor, Fe(III)/Fe(II) cycling rate, and amount of Fe-O-B bond in the {113}/B₄C/H₂O₂ system were shown than those in other systems, thus exhibiting its desirable catalytic performance for •OH production and pollutants oxidation. Iron species and X-ray photoelectron spectroscopy (XPS) analyses indicated that B-B bond and interfacial suboxide boron (e.g., B-O) could provide electrons to facilitate Fe(III) reduction for boosting the Fe(III)/Fe(II) cycling. Density functional theory (DFT) results demonstrated the formation of Fe-O-B bond on hematite {113}, {100}, and {012} facets, which were beneficial to the breakage of O-O bond of bound H₂O₂ molecule and thus improved the generation of •OH. This study emphasized the essential role of B₄C in developing tailored hematite facets as a contaminant remediation substrate, and provided important insights into the design of efficient heterogeneous Fenton-like systems.