Significantly Enhanced Aqueous Cr(VI) Removal Performance of Bi/ZnO Nanocomposites via Synergistic Effect of Adsorption and SPR-Promoted Visible Light Photoreduction

Abstract

Bismuth nanoparticles (BiNPs) and Zinc Oxide photocatalysts (BiNPs/ZnO) with different Bi loadings were successfully prepared via a facile chemical method. Their morphology and structure were thoroughly characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), UV-Vis (Ultraviolet-Visible) diffuse reflectance spectroscopy (DRS), photoluminescence spectra (PL), and electrochemical impedance spectroscopy (EIS). The results showed that a modification of hexagonal wurtzite-phase ZnO nanoparticles with Bi is achievable with an intimate interfacial interaction within its composites. The performance of the photocatalytic Cr(VI) removal under visible light irradiation indicated that BiNPs/ZnO exhibited a superior removal performance to bare ZnO, Bi, and the counterpart sample prepared using a physical mixing method. The excellent performance of the BiNPs/ZnO photocatalysts could be ascribed to the synergistic effect between the considerable physical Cr (VI) adsorption and enhanced absorption intensity in the visible light region, due to the surface plasmon resonance (SPR) as well as the effective transfer and separation of the photogenerated charge carriers at the interface.Very recently, as a semimetal, bismuth (Bi) has been excavated to have direct plasma photocatalytic ability mediated by SPR (surface plasmon resonance) [16]. This property would cause the absorbed electrons to resonate inside the metal, thereby increasing the absorption of photons, and this resonance mostly occurs in the visible light region [17][18][19][20]. Similar to noble metal elements, for instance Au [21,22], Ag [23,24], and Pt [25,26], Bi is also found to be a potential candidate to activate the wide band gap photocatalysts, and is thus widely applied as a cocatalyst due to its SPR effect; many groups have done research in this area [27,28], exploring cocatalysts Bi/CdS [29], Bi/g-C 3 N 4 [18], Bi/Bi 2 O 3 [30], and Bi/(BiO) 2 CO 3 [28]. Wang et al., described that Bi/CdS microspheres could efficiently elevate the visible light photocatalytic activity for methyl orange (MO) degradation, because of its enhanced visible light absorption and quickly charged separation caused by the introduction of Bi [29]. Dong et al., proclaimed that incorporating Bi into the semiconductor g-C 3 N 4 nanosheets showed an improved photodegradation capability of NO under visible light illumination, which could be assigned to the suppression of photodriven electrons-holes pairs, because Bi served as the recipient and communicator of the electron [18].Although photocatalytic degradation of organic pollutants via photo-oxidation has been widely disclosed in most of cases where Bi-based catalysts were employed [31,32], work about the wastewater remediation via photoreduction using Bi cocatalysts was rarely found. In this work, the BiNPs/ZnO composites were prepared herein by an easy eco-friendly synthesis method compared to that reported with a so...

The synergy of N-doped and SPR-promoted photocatalytic removal of NO with graphene/Bi nanocomposites

“…3b). 17 Fig. 3c also conrmed that Bi spheres were randomly distributed on the surface of NG nanosheets.…”

“…The characteristic peaks of 156.6 eV and 161.9 eV were in agreement with the Bi-Bi bonds, and 159.1 eV and 164.4 eV belong to the Bi-O bonds. 17 This proved that Bi was successfully synthesized in 2.0%-NG/Bi, but the appearance of Bi-O bonds was due to the easy oxidation of Bi. 17 The N 1s XPS spectrum of 2.0%-NG/Bi given in Fig.…”

“…17 This proved that Bi was successfully synthesized in 2.0%-NG/Bi, but the appearance of Bi-O bonds was due to the easy oxidation of Bi. 17 The N 1s XPS spectrum of 2.0%-NG/Bi given in Fig. 2c revealed the existence of pyridine N ($398.2 eV), pyrrolic N Fig.…”

Criticial Assessment of the Photocatalytic Reduction of Cr(VI) over Au/TiO2

“…Very often, conversion of Cr(IV) is accompanied with an adsorption (mentioned as removal) [20]; although, these processes work in opposing directions. Thus, some strategies for the full recovery of the initial photocatalyst need to be developed in the future.…”

Facile Synthesis of Heterojunctioned ZnO/Bi2S3 Nanocomposites for Enhanced Photocatalytic Reduction of Aqueous Cr(VI) under Visible-Light Irradiation

“…From Figure 8f, 5%-ZnO/Bi 2 S 3 photocatalyst exhibited no obvious change of the photocatalytic activity after four cycles with the removal rate still reaching 92%, suggesting that no significant damage of the structure of the composites took place and the as-prepared composite photocatalyst had excellent photo-stability and long-term reusability. Compared with bare ZnO with photocorrosion effect [44], the prepared photocatalyst had great potential for water remediation…”