Nano boron carbide effectively boost Fenton-like performance of hematite mediated systems: Roles of hematite exposed facets and synergistic catalysis between Fe and B.

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.