Facile Synthesis of Carbon- and Nitrogen-Doped Iron Borate as a Highly Efficient Single-Component Heterogeneous Photo-Fenton Catalyst under Simulated Solar Irradiation

Abstract

The development of a heterogeneous catalyst for use in environmental remediation remains a challenging and attractive research endeavor. Specifically, for Fenton reactions, most research approaches have focused on the preparation of iron-containing heterostructures as photo-Fenton catalysts that utilize visible light for enhancing the degradation efficiency. Herein, the synthesis and novel application of C,N-doped iron borates are demonstrated as single-component heterogeneous photo-Fenton catalysts with high Fenton activity under visible light. Under the optimal conditions, 10 mg of the catalyst is shown to achieve effective degradation of 10 ppm methylene blue (MB) dye, Rhodamine B (RhB) dye, and tetracycline (TC) under simulated solar irradiation with a first-order rate constant of k = 0.218 min−1, 0.177 min−1, and 0.116 min−1, respectively. Using MB as a model system, the C,N-doped iron borate exhibits 10- and 26-fold increases in catalytic activity relative to that of the 50 nm hematite nanoparticles and that of the non-doped iron borate, respectively, in the presence of H2O2 under the simulated solar irradiation. Furthermore, the optimum reaction conditions used only 320 equivalents of H2O2 with respect to the concentration of dye, rather than the several thousand equivalents of H2O2 used in conventional heterogeneous Fenton catalysts. In addition, the as-prepared C,N-doped iron borate achieves 75% MB degradation after 20 min in the dark, thus enabling the continuous degradation of pollutants at night and in areas with poor light exposure. The stability and recyclability of C,N-doped iron borate for the oxidation of MB was demonstrated over three cycles with insignificant loss in photo-Fenton activity. The high Fenton activity of the C,N-doped iron borate is considered to be due to the synergistic action between the negatively-charged borate ligands and the metal center in promoting the Fenton reaction. Moreover, carbon and nitrogen doping are shown to be critical in modifying the electronic structure and increasing the conductivity of the catalyst. In view of its synthetic simplicity, high efficiency, low cost of reagents, and minimal cost of operation (driven by natural sunlight), the as-prepared heterogeneous single-component metal borate catalyst has potential application in the industrial treatment of wastewater.

Two Novel Visible‐Light‐Active Borate Composites Photocatalysts: 2 %Pt/Gd0.85Ce0.15B5O9 and 2.5 %CuO/Gd0.90Ce0.10B5O9

“…Sun et. al reported that the diffraction peaks of GdB 5 O 9 have an expanding tendency with the increasing substitution of Ce 3+ , which causes the diffraction pattern to shift to a lower angle [21] . By observing the characteristic diffraction peak of (112), a similar phenomenon appears in Figure 1a, because the ionic radius of Ce 3+ is larger than that of Gd 3+ .…”

“…[31] Finally, the photodegradation activity of the 2.5 %CuO/Gd 0.90 Ce 0.10 B 5 O 9 sample still has stable photocatalytic performance after four cycles. It should be particularly noted that the choice of RhB, a cationic dye, as model contamination for the photo-oxidation reaction in this paper is based on the choice of literature research, [6][7][8][9][19][20][21] as shown in Table 1, where cationic dyes, such as RhB and methylene blue (MB), are mostly chosen for the application of borate photocatalysts for the degradation of dyes.…”

“…Up to now, a small number of borate photocatalysts exhibit photocatalytic activity under visible light illumination. For instance, the Bi 4 B 2 O 9, [19] BiO 2 [BO 2 (OH)], [19] CsCdBO 3, [20] and FeBO 3 [21] displayed photocatalytic performances in visible light. And it is known from a review previously reported by the authors that there are no studies on the mineralization of inorganic heavy metal ions, such as reducing hexavalent chromium ions, in borate photocatalysis.…”

Structural Regulation and Oxygen Reduction Reaction Activity of [Co(bpy)2BO2(OH)] and [Cu(bpy)(OH)]2– Complex Templated Borates

“…Borate catalysts have developed rapidly due to their environmental friendliness, abundant reserves, and low cost. − Panomsuwan’s group synthesized a B-doped nanomaterial (BCNP) . Compared with undoped CNP, BCNP showed enhanced activity for oxygen reduction reaction (ORR) in an alkaline solution.…”