Insight into Potassium Vanadates as Visible-Light-Driven Photocatalysts: Synthesis of V(IV)-Rich Nano/Microstructures for the Photodegradation of Methylene Blue

Abstract

Photocatalysis is regarded as a promising tool for wastewater remediation. In recent years, many studies have focused on investigating novel photocatalysts driven by visible light. In this study, K 2 V 6 O 16 · n H 2 O nanobelts and KV 3 O 8 microplatelets were synthesized and investigated as photocatalysts. Samples were obtained via the facile method based on liquid-phase exfoliation with ion exchange. By changing the synthesis temperature (20–80 °C), different compositions, morphologies, and V 4+ /V 5+ ratios were obtained and investigated as photocatalysts for organic dye degradation. Potassium vanadates’ structural, morphological, and optical properties were characterized using X-ray diffraction(XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Physical Property Measurement System (PPMS), thermogravimetric analysis (TGA) with mass spectrometry (MS), N 2 adsorption, scanning electron microscopy (SEM), photoluminescence (PL), and UV–vis diffuse reflectance spectroscopy (DRS). Synthesized K 2 V 6 O 16 · n H 2 O and KV 3 O 8 showed an efficient absorption in the visible wavelength region with a narrow band gap energy of 1.80 and 1.91 eV, respectively. Their photocatalytic activity was evaluated by the degradation of methylene blue (MB) under simulated solar light illumination. The KV 3 O 8 microplatelets exhibited the greatest photocatalytic activity, resulting in more than 90% degradation of the dye within the first 30 min. It is suggested that the observed excellent photocatalytic performance is attributed to the high content of V 4+ species. Furthermore, the influence of active species was investigated, and the mechanism responsible for the photodegradation of the MB dye was discussed for the first time for potassium vanadates.

New light on the photocatalytic performance of NH4V4O10 and its composite with rGO

“…Nevertheless, a band at approximately 460 nm was registered. Similar behaviour was already observed for K-containing vanadate-K 2 V 6 O 16 •0.65H 2 O 19 . Taking into account that the energy band gap estimated from the UV-vis spectrum equals approximately 2.28 eV (~ 543 nm), the observed emission band is not related to the conduction to valence band transition.…”

“…Moreover, the proposed combination of NH 4 V 4 O 10 with rGO not only increases the photocatalytic degradation reaction rate and improves the cyclic stability of photocatalyst but also widens its application, allowing for the efficient photoreduction of toxic Cr(VI). In comparison to other vanadiumbased photocatalysts reported in the literature 19,[58][59][60][61][62][63][64][65] (Tables S1 and S2), NVO and NVO/rGO present better or similar efficiency towards the photodegradation of MB and Cr(VI). Importantly, proposed photocatalysts can be www.nature.com/scientificreports/ activated under solar light and exhibit significant photocatalytic degradation of pollutants within the first 60 min of illumination.…”

“…Recently, we proposed using a simple potassium salt (potassium formate) as a promising alternative for the synthesis of visible-light-driven photocatalysts. The obtained potassium vanadates (KV 3 O 8 , K 2 V 6 O 16 •nH 2 O) exhibited excellent photocatalytic activity, resulting in more than 90% degradation of methylene blue (MB) within the first 30 min 19 .…”

Chemical looping methanol oxidation using supported vanadium phosphorous oxide carriers for formaldehyde production

“…(516.6 eV and 524.2 eV). [56][57][58][59][60][61][62][63][64] However, aer both carriers undergo redox cycling, the ratio of V 4+ to V 5+ on the surface increases. This can be attributed to higher oxygen vacancies present on the surface aer 10 redox cycles.…”

New updates on vanadate compounds synthesis and visible-light-driven photocatalytic applications

“…[70]. Further, other techniques such as the soft template approach [71,72], polymerization [73], liquid-phase exfoliation by ion exchange [74], reverses microemulsion [75], and reactive magnetron sputtering [76] have been studied in order to design and fabricate vanadate photocatalysts.…”