Bi2O2CO3 Nanosheets Research Articles

Fe-doped hollow PtBi nanocages loaded on Bi2O2CO3-NC composite support with excellent methanol electrooxidation performance

A highly active and stable anode catalyst for direct methanol fuel cells is critical to commercialization. Therefore, we have synthesized a unique Fe-doped catalyst Fe–PtBi2/Bi2O2CO3-NC through the classical hydrothermal method and sodium borohydride reduction. Physical characterizations confirm the existence of Bi2O2CO3 nanosheets and successful loading of PtBi nanocages. It is the alternating layer arrangement of Bi2O2CO3, the bifunctional mechanism of PtBi alloy and the synergistic effect of each component that make the synthesized Fe–PtBi2/Bi2O2CO3-NC possess such remarkable methanol oxidation reaction activity (a mass activity of 9345 mA/mgPt in alkaline electrolyte). Moreover, electrochemical measurements also indicate that 51.7% of the mass activity was retained after 1 h durable operation, which is approximately 4.1 times than that of commercial Pt black. Fe–PtBi2/Bi2O2CO3-NC may be applied as a promising alkaline anode catalyst for direct methanol fuel cells due to its outstanding structure and performance. The specific work provides a reference for designing reliable structures and selection of doping elements to enhance the sluggish kinetics of methanol electrooxidation.

Sonochemical Synthesis of Large Two‐Dimensional Bi2O2CO3 Nanosheets for Hydrogen Evolution in Photocatalytic Water Splitting

AbstractLaterally large (≈3 µm), atomically thin 2D Bi2O2CO3 nanosheets (2D bismuth oxycarbonate, 2D bismutite) are fabricated via sonochemically assisted, template‐free synthesis. Keys to the synthesis of the freestanding, laterally large 2D Bi2O2CO3 nanosheets from bulk Bi powder are choice of suspension medium, controlled reaction temperatures, and several hours processing time. Lateral sizes of 2D Bi2O2CO3 can be controlled between µm‐sized nanosheets and tens of nm sized nanoflakes solely based on the choice of suspension medium. The here introduced 2D Bi2O2CO3 nano‐sheets/‐flakes are then hybridized by a simple mix‐and‐match approach with TiO2 nanoparticles for testing in suspension‐type photocatalytic hydrogen production via water splitting. This introduces the 2D Bi2O2CO3 as a prospective noble‐metal‐free catalyst component with TiO2 for photocatalytic hydrogen evolution, beyond Bi2O2CO3's current use as photocatalyst for organic pollutant degradation. These results enrich the fabrication toolbox of emerging 2D pnictogen oxycarbonates toward large 2D nanosheets and demonstrate the potential of 2D Bi2O2CO3 as a catalyst component for hydrogen evolution in photocatalytic water splitting.

Synthesis of Bi2O2CO3/In(OH)3·xH2O nanocomposites for isopropanol sensor with excellent performances at low temperature

The ability to detect a volatile organic compound in real-time, such as isopropanol (IPA) gas, is critical for human health and safety protection, especially since the sensor can operate at low temperatures and behave outstanding sensing performances. Herein, the Bi2O2CO3/In(OH)3·xH2O nanocomposites are synthesized using a two-step hydrothermal process, particularly the surfaces of Bi2O2CO3 (BCO) nanosheets were embellished with In(OH)3·xH2O nanoparticles. It is found that the BCO/In(OH)3·xH2O sensors exhibit an excellent response of 20.39, wide concentration detection range from 1 to 1000 ppm, the working temperature as low as 100 ºC, and the rapid response/recovery times of 5 s and 4 s towards 100 ppm IPA. On the other hand, the selectivity of the BCO/In(OH)3·xH2O sensor towards IPA is eye-catching. In particular, the enhanced IPA sensing performances might be attributed to the large specific area (52.46 m2/g). The increased conductivity of BCO/In(OH)3·xH2O nanocomposites due to incorporation of the In(OH)3·xH2O, which can significantly promote the surface-catalyzed reaction between oxygen species such as O- and IPA molecules.

Sub-2 nm ultra-thin Bi2O2CO3 nanosheets with abundant Bi-O structures toward formic acid electrosynthesis over a wide potential window

Sub-2 nm ultra-thin Bi2O2CO3 nanosheets with abundant Bi-O structures toward formic acid electrosynthesis over a wide potential window

Synthesis of ultrathin, porous and surface modified Bi2O2CO3 nanosheets by Ni doping for photocatalytic organic pollutants degradation

BackgroundIn recently years, the organic pollutants removal using semiconductor photocatalysis has attracted significant interest, however, the insufficient visible-light-harvesting ability and fast photogenerated charge recombination of photocatalysts vastly hinder their practical application. MethodsIn this work, a facile hydrothermal method was developed for the preparation of Ni doped ultrathin-layered and porous Bi2O2CO3, thus the enhanced light absorption and charge separation were simultaneously achieved. Significant FindingsThe experimental and characterization results show that the formation of ultrathin porous structure can promote multiple scattering of the light, thus enhancing light absorption. Moreover, the adjustment of electronic structure enhances the charge transfer rate greatly and suppresses the recombination of charge carriers. Consequently, the rhodamine B (RhB) photodegradation efficiency of Ni-Bi2O2CO3 has an obvious improvement, which is 8.94-fold higher than pristine Bi2O2CO3. And the primary active species are ·O2− and ·OH radicals in the photocatalytic reaction. Moreover, the degradation pathway of RhB is studied by LC-MS technology and a probable degradation pathway is presented. This work offers an efficacious strategy for synergistically modulating and optimizing photocatalysts and provides an efficient photocatalyst for wastewater treatment.

Sulfur boosting CO2 reduction activity of bismuth subcarbonate nanosheets via promoting proton-coupled electron transfer

Bismuth (Bi) based nanomaterials are attractive catalysts for electrochemical CO2 reduction to formate, while both high selectivity and high activity still need further investigation. Herein, we report a facile strategy, via introducing sulfur (S) atoms to modulate the electronic structure of two-dimensional (2D) bismuth subcarbonate Bi2O2CO3 (BiOC) nanosheets, to improve their catalytic activity meanwhile maintain high formate selectivity. The lower electronegativity of the substituted S than O enhances the local electron density around Bi active sites, promoting the proton-coupled electron transfer to the CO2 intermediate, and thus contributing to the superior CO2 reduction performance with the selectivity of formate >90% in a wide negative potential range and high partial current density up to 29.0 mA cm−2 at −0.9 vs RHE. This study provides an in-depth understanding on the design of advanced CO2 reduction electrocatalysts via heteroatom doping.

Ultrastable and Efficient Visible-light-driven CO2 Reduction Triggered by Regenerative Oxygen-Vacancies in Bi2 O2 CO3 Nanosheets.

Herein, we first design a fast low-pressure ultraviolet light irradiation strategy for easily regenerating the nearly equivalent surface vacancies. Taking the defective Bi2 O2 CO3 nanosheets as an example, nearly equal amount of oxygen vacancies can be regenerated under UV light irradiation. Synchrotron-radiation quasi in situ X-ray photoelectron spectra disclose the Bi sites in the O-defective Bi2 O2 CO3 nanosheets can act as the highly active sites, which not only help to activate CO2 molecules, but also contribute to stabilizing the rate-limiting COOH* intermediate. Also, in situ Fourier transform infrared spectroscopy and in situ mass spectrometry unravel the UV light irradiation contributes to accelerating CO desorption process. As a result, the O-defective Bi2 O2 CO3 nanosheets achieve a stability up to 2640 h over 110 cycling tests and a high evolution rate of 275 μmol g-1 h-1 for visible-light-driven CO2 reduction to CO.

Ultrastable and Efficient Visible‐light‐driven CO2 Reduction Triggered by Regenerative Oxygen‐Vacancies in Bi2O2CO3 Nanosheets

AbstractHerein, we first design a fast low‐pressure ultraviolet light irradiation strategy for easily regenerating the nearly equivalent surface vacancies. Taking the defective Bi2O2CO3 nanosheets as an example, nearly equal amount of oxygen vacancies can be regenerated under UV light irradiation. Synchrotron‐radiation quasi in situ X‐ray photoelectron spectra disclose the Bi sites in the O‐defective Bi2O2CO3 nanosheets can act as the highly active sites, which not only help to activate CO2 molecules, but also contribute to stabilizing the rate‐limiting COOH* intermediate. Also, in situ Fourier transform infrared spectroscopy and in situ mass spectrometry unravel the UV light irradiation contributes to accelerating CO desorption process. As a result, the O‐defective Bi2O2CO3 nanosheets achieve a stability up to 2640 h over 110 cycling tests and a high evolution rate of 275 μmol g−1 h−1 for visible‐light‐driven CO2 reduction to CO.

Facile synthesis of CeO2/carbonate doped Bi2O2CO3 Z-scheme heterojunction for improved visible-light photocatalytic performance: Photodegradation of tetracycline and photocatalytic mechanism

CeO2 nanoparticles are successfully loaded on carbonate doped Bi2O2CO3 (CBOC) nanosheets by a facile hydrothermal and low-temperature calcination method. CeO2/CBOC heterojunction shows significantly enhanced photocatalytic activity, when 35 mg of CeO2/CBOC photocatalyst is added to tetracycline (TC) solution (20 mg/L, 100 mL), about 79.5% TC is degraded within 90 min under visible light irradiation, which is much higher than that of original CeO2 and CBOC. According to photoelectrochemical characterization and active radical capture experiments, the Z-scheme electron transfer mechanism is the reason for the significant enhancement of photocatalytic activity. Besides, the XPS results indicate that Ce4+/Ce3+ redox pairs are formed at the contact interface between CeO2 and CBOC, which is conducive to the transfer of photoexcited electrons and production of superoxide radicals. Additionally, the photocatalytic mechanism and possible degradation pathway of TC is proposed through free radical trapping experiments and liquid chromatography-mass (LC-MS) analysis. This study will accumulate experience for the combination of CeO2 and bismuth-based nanomaterials, and provide a feasible way to design wide band-gap bismuth-based photocatalysts, thereby achieving efficient visible light degradation of environmental pollutants.

Few-layer Bi2O2CO3 nanosheets derived from electrochemically exfoliated bismuthene for the enhanced photocatalytic degradation of ciprofloxacin antibiotic.

Few-layer two-dimensional (2D) Bi2O2CO3 nanosheets with a thickness of 4–5 nm were successfully fabricated via electrochemical exfoliation, followed by an exposure to ambient conditions. The formation process for these nanosheets was explored through ex situ X-ray diffractometer. The photocatalytic capacity of 2D Bi2O2CO3 nanosheets was investigated towards the degradation of ciprofloxacin. It was shown that 2D Bi2O2CO3 nanosheets exhibited better catalytic performance than Bi2O2CO3 nanoparticles synthesized by hydrothermal method under UV-Vis light irradiation. The enhanced photocatalytic activity is due to the larger specific surface area, as well as the lower band gap. Additionally, the radical trap experiments demonstrate that holes and hydroxyl radicals are of great importance in the degradation of ciprofloxacin. Finally, the 2D Bi2O2CO3 nanosheets show high stability in the photocatalytic degradation of ciprofloxacin, and could have a prospective application in the treatment of antibiotic wastewater.

Hierarchical BiOHC2O4/Bi2O2CO3 composite microrods fabricated via insitu anion ion-exchange and their advanced photocatalytic performance

Abstract BiOHC2O4 microrods as the template were first synthesized via a facile microwave hydrothermal method. Then, BiOHC2O4/Bi2O2CO3 microrods and Bi2O2CO3 nanosheets with hierarchical structure were in-situ synthesized at room temperature by carbonate ion-exchange using BiOHC2O4 crystals as a template. The obtained hierarchical BiOHC2O4/Bi2O2CO3 microrods and Bi2O2CO3 nanosheets displayed superior texture properties in aqueous photocatalytic reactions, e.g. low density, large specific surface area and good dispersion. Therefore, these hierarchical BiOHC2O4/Bi2O2CO3 microrods possessed excellent photocatalytic activity for azo dye methyl orange (MO) degradation. The reason for the high photocatalytic performance of BiOHC2O4/Bi2O2CO3 microrods could be due to their unique interface which endows with efficient light harvesting capability and high carrier separation and utilization. Radical capture test confirmed that more h+ and ·O2− were produced over this unique hierarchical BiOHC2O4/Bi2O2CO3 heterojunction. A possible reaction pathway involved two-electrons reduction of oxygen for promoting photocatalytic degradation efficiency of MO was proposed.

Smart Removal of Dye Pollutants via Dark Adsorption and Light Desorption at Recyclable Bi2O2CO3 Nanosheets Interface.

The adsorbents for water treatment and purification are commonly not recyclable because of the lack of a reagent-less "switch" to readily release the adsorbed compounds. Herein, the interface of Bi2O2CO3 (BOC) nanosheets is designed, synthesized, and modified with citric acid, namely, modified Bi2O2CO3 (m-BOC). The m-BOC is able to selectively adsorb methylene blue (MB) in the dark and the adsorbed MB could be released in the light from m-BOC without the addition of any chemicals. The adsorption mechanism is attributed to the electrostatic attraction between positively charged MB and the negatively charged surface of m-BOC. In contrast, the desorption of MB has resulted from the photo-induced charge redistribution on the surface of m-BOC, which unlocks the coordination bond between m-BOC and the carboxylic group. As a result, BOC is recycled. Such a mechanism was verified by both experimental investigation and DFT calculation. This work provides a promising interfacial engineering strategy for the remediation of dye-polluted water and smart separation in chemical engineering.

(002) Oriented Bi2O2CO3 Nanosheets with Enhanced Photocatalytic Performance for Toluene Removal in Air

Layer-structured Bi2O2CO3 is a novel photocatalyst for eliminating environmental pollutants. In this work, Bi2O2CO3 nanosheets were synthesized by hydrothermal methods, followed by annealing in nitrogen. (002) oriented Bi2O2CO3 nanosheets were obtained and characterized by XRD, SEM, XPS, BET and UV-Vis diffuse reflectance spectra. Photocatalytic properties were investigated by toluene removal in air, with the assistant of Bi2O2CO3 nanosheets under artificial irradiation. Our results show that Bi2O2CO3 annealed in nitrogen exhibited high full-light-driven photocatalytic activity for toluene photocatalytic decomposition, which may be ascribed to facet orientation evolution during the annealing process and enhanced efficient charge separation. The sample annealed at 150 °C for 8 h (BOC-150-8 h) showed high stability and the highest toluene removal rate, which was up to 99%. The final degradation products were detected by gas chromatography–mass spectrometer (GC-MS) and CO2 was verified to be the primary product. Photocatalytic mineralization of toluene in air over Bi2O2CO3 was proposed. This work may provide a foundation for application of annealed Bi2O2CO3 in indoor air purification.

The in situ morphology transformation of bismuth-based catalysts for the effective electroreduction of carbon dioxide

An in situ morphological transformation phenomenon accompanied by petal-shaped Bi2O2CO3 nanosheets formation has been observed to help improving electrocatalytic performance.

Bi metal prevents the deactivation of oxygen vacancies in Bi2O2CO3 for stable and efficient photocatalytic NO abatement

Surface oxygen vacancies can normally enhance photocatalytic activity, but also easily suffers from instability and deactivation in continuous photocatalytic purification of air pollutants. Therefore, it is necessary to develop an effective method to improve the photocatalytic stability of oxygen vacancies. In this work, Bi metal nanoparticle decorated Bi2O2CO3 nanosheets with oxygen vacancy (Bi@OV-BOC) are fabricated and exhibited higher photocatalytic activity and stability than Bi2O2CO3 with oxygen vacancy (OV-BOC). The co-effect of Bi metal nanoparticles and oxygen vacancies could also effectively inhibit the formation of toxic intermediates (NO2) and promote it to form final products (NO3−). First-principles density functional theory (DFT) calculation and experimental results suggested that the co-effects of Bi metal nanoparticles and oxygen vacancies (OVs) can largely promote the separation and transfer of photo-generated electron and hole to generate abundant active radicals. More importantly, the Bi metal nanoparticles could be as the active site to activate O2 and H2O molecules so that the O2 and H2O molecules would not fill into oxygen vacancies, resulting in preventing the deactivation of oxygen vacancies. The sufficient active radicals can realize complete oxidation of intermediates into final products and avoid toxic intermediates (e.g. NO2) accumulation. This study reveals the co-effects of Bi and OVs in defective photocatalyst, and also provides fundamental guidance for maintaining the active role of oxygen vacancies.

Ultrasonic-assisted fabrication of a direct Z-scheme BiOI/Bi2O4 heterojunction with superior visible light-responsive photocatalytic performance

Z-scheme heterojunctions photocatalysts for the transfer and separation efficiency of carriers are increasingly popular. Here, a direct Z-scheme BiOI/Bi2O4 heterojunction was successfully constructed via an ultrasonic-assisted hydrothermal method. X-ray diffraction, high resolution transmission electron microscopy, and X-ray photoelectron spectroscopy results confirmed the successful construction of the BiOI/Bi2O4 heterojunction. The optimized BiOI/Bi2O4 photocatalyst offered enhanced degradation rates under visible light: these values were approximately 2.8- and 30-fold higher than Bi2O4 and BiOI, respectively. Interestingly, the ultrathin, in-situ prepared Bi2O2CO3 nanosheets grew on the surface of a BiOI/Bi2O4 heterojunction under visible light irradiation, and the presence of the resulting Bi2O2CO3 further increased the degradation efficiency. This was confirmed using photoluminescence and electrochemical impedance spectroscopy studies. The Z-scheme electron transfer paths contribute to faster separation and transfer of photo-generated carriers. The radical trapping experiments certified that holes and superoxide radicals were the main active species. Furthermore, the positions of the conduction band of BiOI and Bi2O4 samples were investigated via Mott-Schottky measurements. Finally, a Z-scheme photocatalytic mechanism was proposed for the BiOI/Bi2O4 heterojunction. This work provides an effective strategy to construct Z-scheme heterojunctions for removal of organic pollutants.

Enhanced degradation of rhodamine B, tetracycline and carbamazepine by construction of a solar driven indirect Z-scheme AgI/Ag/Bi2O2CO3 nanosheets photocatalyst

The indirect Z-scheme AgI/Ag/Bi2O2CO3 nanosheets photocatalysts were facilely constructed with Ag nanoparticles generated between AgI and Bi2O2CO3 nanosheets through in situ photo-reduction process. The morphology, structure, chemical composition, optical and photo-electrochemical properties were characterized via various methods. Different organic pollutants, including Rhodamine B (RhB), Tetracycline (TC) and Carbamazepine (CBZ) were used to explore the photodegrading application of AgI/Ag/Bi2O2CO3 nanosheets. AgI/Ag/Bi2O2CO3 nanosheets exhibited highly improved photocatalytic activities than that of Bi2O2CO3 nanosheets (BOC sheets), AgI/BOC sheets and AgI. The photocatalytic rates of RhB, TC and CBZ degradation on AgI/Ag/Bi2O2CO3 nanosheets were 2.48, 1.31 and 7.61 times higher than that of BOC sheets, respectively. The as constructed indirect Z-scheme structure may be the main factor to increase the photocatalytic performance of AgI/Ag/Bi2O2CO3 nanosheets, where Ag can act as charge transfer bridge accelerating the charge transfer and separation of the electrons and holes. Moreover, it may also result in higher oxidative holes in VB of Bi2O2CO3 and more reductive electrons in CB of AgI. The photocatalytic mechanism on the AgI/Ag/Bi2O2CO3 nanosheets was also discussed based on the trapping experiment results that ·O2− and h+ were the main radicals during photocatalytic reaction. The present study may provide a rational strategy to design highly efficient indirect Z-scheme photocatalyst for organic pollutants degradation.

Pivotal roles of artificial oxygen vacancies in enhancing photocatalytic activity and selectivity on Bi2O2CO3 nanosheets

There is an increasing interest in bismuth carbonate (Bi2O2CO3, BOC) as a semiconductor photocatalyst. However, pure BOC strongly absorbs ultraviolet light, which drives a high recombination rate of charge carriers and thereby limits the overall photocatalysis efficiency. In this work, artificial oxygen vacancies (OV) were introduced into BOC (OV-BOC) to broaden the optical absorption range, increase the charge separation efficiency, and activate the reactants. The photocatalytic removal ratio of NO was increased significantly from 10.0% for pure BOC to 50.2% for OV-BOC because of the multiple roles played by the oxygen vacancies. These results imply that oxygen vacancies can facilitate the electron exchange between intermediates and the surface oxygen vacancies in OV-BOC, making them more easily destroyed by active radicals. In situ DRIFTS spectra in combination with electron spin resonance spectra and density functional theory calculations enabled unraveling of the conversion pathway for the photocatalytic NO oxidation on OV-BOC. It was found that oxygen vacancies could increase the production of active radicals and promote the transformation of NO into target products instead of toxic byproducts (NO2), thus the selectivity is significantly enhanced. This work provides a new strategy for enhancing photocatalytic activity and selectivity.

Br-doped Bi2O2CO3 nanosheets with improved electronic structure and accelerated charge migration for outstanding photocatalytic behavior

The work presents a combinative merit of non-metal ion doping and active facet effect of Bi2O2CO3 photocatalyst. Br-doped Bi2O2CO3 nanosheets with exposed {0 0 1} facets were facilely prepared via a one-step hydrothermal reaction with the assistance of cetyltrimethylammonium bromide (CTAB) at a mild temperature of 60 °C for 4 h. The presence of CTAB not only influences the growth of Bi2O2CO3 crystalline but also leads to a Br-doping. Based on the crystal structure and DFT calculation, bromine from CTAB as dopant interstitially incorporates into Bi2O2CO3 lattice, which alters the band gap positions of Bi2O2CO3 and generates delocalized impurity states at the Fermi level. The improved electronic structure endows Br-doped Bi2O2CO3 with a broadened light-harvesting and accelarated charge migration. In addition, the thin nanosheet means more exposure of {0 0 1} active facets and larger internal electric field, which would also benefit for the charge separation. The sample with a trace Br content of 1.17 wt% shows the best degradation efficiency for RhB with a rate constant k enhanced by 3.6 folds compared with that of pure Bi2O2CO3 under simulated solar irradiation. Combining the effective catalytic sites and the detected active species, a possible migration mechanism of photogenerated e−/h+ pairs on the surface of Br-doped Bi2O2CO3 nanosheet is proposed. The work provides some new insights into the rational design and synthesis of non-metal doped semiconductor photocatalyst with facet dependency.

Formamide-assisted one-pot synthesis of a Bi/Bi2O2CO3 heterojunction photocatalyst with enhanced photocatalytic activity

Herein, we fabricate a Bi/Bi2O2CO3 heterojunction via one-pot in situ deposition of Bi nanoparticles on Bi2O2CO3 nanosheets, using formamide both as a carbon/alkali source and a reductant and demonstrate that the content of Bi in Bi/Bi2O2CO3 composites can be tuned by adjusting the hydrothermal reaction time. Systematic characterization and analysis of as-prepared composites revealed that the initial in situ growth of Bi nanoparticles on BiOCOOH (an intermediate formed during the decomposition of formamide) was followed by the reaction of BiOCOOH with CO32− to afford Bi2O2CO3 nanosheets. The photocatalytic activity (PCA) of Bi/Bi2O2CO3 was evaluated by degradation of rhodamine B (RhB) under simulated solar light irradiation, and the best result (99.61% degradation efficiency after 50-min irradiation) was observed for the photocatalyst obtained after 12-h hydrothermal treatment. The enhanced photocatalytic performance was ascribed to visible-light harvesting and electron-hole separation efficiency improvements caused by the surface plasmon resonance of Bi nanoparticles. Moreover, the developed photocatalyst displayed high photochemical stability and reusability during ten photocatalytic cycling runs and was therefore concluded to be well suited for practical wastewater purification applications. Thus, this work provides a new and facile method of utilizing non-noble Bi nanoparticles to optimize the PCA of semiconductor materials.