Efficient Removal of Azo-Dyes in Aqueous Solution by CeB₆Nanocrystals

Abstract

Rare earth oxides have been well-developed for the treatment of synthetic dyes in wastewater, but limited information is known regarding the application of other rare earth containing materials in this field. Herein, cerium hexaborides (CeB6) were synthesized via the reaction of CeF3 and NaBH4 in molten LiCl–KCl at 900 °C. Homogeneously dispersed CeB6 nanocrystals exhibit great performances for the removal of azo-dyes such as Congo red (CR). It follows pseudo-second-order kinetics, and a maximum removal capacity of 775.6 mg g–1 was obtained. On the basis of the results from adsorption–desorption tests, TEM, and XPS, both adsorption and photocatalytic degradation contribute to the CR removal process. Hydroxyl (•OH) radicals are the major active species involved in the photocatalytic degradation while superoxide (•O2 –) radicals and holes (h + ) play minor roles as made evident by the radical quenching and ESR results.

α-MoB2 Nanosheets for Hydrogen Evolution in Alkaline and Acidic Media

“…Four oxidation states were identified by deconvolution of the high-resolution Mo 3d XPS spectrum. Mo 0 corresponds to the molybdenum of molybdenum boride, while Mo 3+ , Mo 5+ , and Mo 6+ should result from the surface oxidation of α-MoB 2 (Figure a) that are in line with the results of the molybdenum boride materials reported previously. , Figure b shows the B 1s region, and the intense peak at 188.21 eV corresponds to B in molybdenum boride, which is almost the same as that in other molybdenum borides. , Amorphous B and boron suboxides should be responsible for the 186.61 and 192.36 eV peaks. , …”

“…20,23 Figure 2b shows the B 1s region, and the intense peak at 188.21 eV corresponds to B in molybdenum boride, which is almost the same as that in other molybdenum borides. 23,41 Amorphous B 32 and boron suboxides should be responsible for the 186.61 and 192.36 eV peaks. 41,42 SEM and TEM were employed to explore the morphology and microstructure of the as-prepared α-MoB 2 .…”

“…As a simple and versatile route, molten salt synthesis allows for the synthesis of metal boride nanoparticles with controllable phases and morphologies. − Recently, a class of nanoscale transition metal diborides, including α-MoB 2 , have been synthesized through the metal oxide and boron reactions in the NaCl/KCl molten salt . However, the α-MoB 2 synthesized in molten salt exhibited a lower HER activity in acidic electrolyte than the α-MoB 2 nanoparticles prepared by the SSM method .…”

Critical Review on Synthetic Routes and Catalytic Applications of Hollow Nanomaterials

“…[123] Ceramic Templates: Hollow nanoboxes could synthesize by templating against copper oxide nanocubes. [124] Inorganic and complex salts by hard template strategy:…”

A Simple Molten Salt Route to Crystalline β-MoB2 Nanosheets with High Activity for the Hydrogen Evolution Reaction

“…It has been reported that molten salt synthesis is a simple and versatile route that favors the phase and size controllable preparation of metal boride nanoparticles. − This method has been used to prepare nanoscale electrocatalysts, including oxides and borides. − For β-MoB 2 , although it is intrinsically less active than α-MoB 2 as an electrocatalyst for the HER due to the presence of both flat graphene-like and puckered phosphorene-like B layers, it is possible to significantly improve its electrocatalytic performance via nanostructuring, which favors a larger surface area . Herein, single-crystalline phase β-MoB 2 nanosheets were synthesized for the first time via the reaction of MoCl 3 and B powders in molten LiCl-KCl for 4 h at 850 °C.…”