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The disposal of dye-contaminated wastewater is a major concern around the world for which a variety of techniques are used for its treatment. The photocatalytic treatment of dye-contaminated wastewater is one of the treatment methods. Semiconductor-assisted photocatalytic treatment of dye-contaminated wastewater has gained pronounced attention recently. This review outlines the recent advancements in the photocatalytic treatment of dye-contaminated wastewater. The photocatalytic degradation of dyes follows three types of mechanisms: (1) dye sensitization through charge injection, (2) indirect dye degradation through oxidation/reduction, and (3) direct photolysis of dye. Several experimental parameters like initial concentration of dyes, pH, and catalyst dosage significantly affect the photocatalytic degradation of dyes. The photocatalytic materials can be categorized into three generations. The single-component (e.g., ZnO, TiO 2 ) and multiple component semiconductor metal oxides (e.g., ZnO–TiO 2 , Bi 2 O 3 –ZnO) are categorized as first-generation and second-generation photocatalysts, respectively. The photocatalysts dispersed on an inert solid substrate (e.g., Ag–Al 2 O 3 , ZnO–C) are classified as third-generation photocatalysts. Finally, we reviewed the challenges that affect the photocatalytic degradation of dyes.

The photofixation and utilization of CO 2 via single-electron mechanism is considered to be a clean and green way to produce high-value-added commodity chemicals with long carbon chains. However, this topic has not been fully explored for the highly negative reduction potential in the formation of reactive carbonate radical. Herein, by taking Bi 2 O 3 nanosheets as a model system, we illustrate that oxygen vacancies confined in atomic layers can lower the adsorption energy of CO 2 on the reactive sites, and thus activate CO 2 by single-electron transfer in mild conditions. As demonstrated, Bi 2 O 3 nanosheets with rich oxygen vacancies show enhanced generation of •CO 2 – species during the reaction process and achieve a high conversion yield of dimethyl carbonate (DMC) with nearly 100% selectivity in the presence of methanol. This study establishes a practical way for the photofixation of CO 2 to long-chain chemicals via defect engineering. The photofixation and utilization of CO 2 is considered to be a clean and green way to produce high-value-added commodity chemicals, but production of long chain chemicals through this process remains a challenge. Here, the authors develop a practical way for the photofixation of CO 2 to long-chain chemicals via defect engineering.

Oxide-ion conductors are important in various applications such as solid-oxide fuel cells. Although zirconia-based materials are widely utilized, there remains a strong motivation to discover electrolyte materials with higher conductivity that lowers the working temperature of fuel cells, reducing cost. Oxide-ion conductors with hexagonal perovskite related structures are rare. Herein, we report oxide-ion conductors based on a hexagonal perovskite-related oxide Ba 7 Nb 4 MoO 20 . Ba 7 Nb 3.9 Mo 1.1 O 20.05 shows a wide stability range and predominantly oxide-ion conduction in an oxygen partial pressure range from 2 × 10 −26 to 1 atm at 600 °C. Surprisingly, bulk conductivity of Ba 7 Nb 3.9 Mo 1.1 O 20.05 , 5.8 × 10 −4 S cm −1 , is remarkably high at 310 °C, and higher than Bi 2 O 3 - and zirconia-based materials. The high conductivity of Ba 7 Nb 3.9 Mo 1.1 O 20.05 is attributable to the interstitial-O5 oxygen site, providing two-dimensional oxide-ion O1−O5 interstitialcy diffusion through lattice-O1 and interstitial-O5 sites in the oxygen-deficient layer, and low activation energy for oxide-ion conductivity. Present findings demonstrate the ability of hexagonal perovskite related oxides as superior oxide-ion conductors. Oxide-ion conductors are important in various applications for clean energy. Here, authors report high oxide-ion conductivity of hexagonal perovskite-related oxide Ba 7 Nb 3.9 Mo 1.1 O 20.05 , which is ascribed to the interstitialcy diffusion and low activation energy for oxide-ion conductivity.

Catalytic deterioration during electrocatalytic processes is inevitable for conventional composite electrodes, which are prepared by depositing catalysts onto a rigid current collector. In contrast, metals that are liquid at near room temperature, liquid metals (LMs), are potential electrodes that are uniquely flexible and maneuverable, and whose fluidity may allow them to be more adaptive than rigid substrates. Here we demonstrate a self-healing electrocatalytic system for CO 2 electroreduction using bismuth-containing Ga-based LM electrodes. Bi 2 O 3 dispersed in the LM matrix experiences a series of electrohydrodynamic-induced structural changes when exposed to a tunable potential and finally transforms into catalytic bismuth, whose morphology can be controlled by the applied potential. The electrohydrodynamically-induced evolved electrode shows considerable electrocatalytic activity for CO 2 reduction to formate. After deterioration of the electrocatalytic performance, the catalyst can be healed via simple mechanical stirring followed by in situ regeneration by applying a reducing potential. With this procedure, the electrode’s original structure and catalytic activity are both recovered. Self-healing electrodes may offer opportunities to prevent catalyst deterioration during electrocatalytic reactions. Here the authors demonstrate a self-healing system by exploiting electrohydrodynamics induced evolution of Bi in liquid metal and apply this to CO 2 electroreduction to formate.

HighlightsCatalytically inert 2D Bi2O3 is activated for boosting electrochemical hydrogen evolution reaction (HER) via oxygen vacancy concentration modulation.The relationship between the varied oxygen vacancy concentrations and the corresponding HER activity is revealed by both experimental Vo verification and theoretical density-functional theory calculations.This work provides insights into activating catalytically inert materials into high-performance catalysts.Oxygen vacancies (Vo) in electrocatalysts are closely correlated with the hydrogen evolution reaction (HER) activity. The role of vacancy defects and the effect of their concentration, however, yet remains unclear. Herein, Bi2O3, an unfavorable electrocatalyst for the HER due to a less than ideal hydrogen adsorption Gibbs free energy (ΔGH*), is utilized as a perfect model to explore the function of Vo on HER performance. Through a facile plasma irradiation strategy, Bi2O3 nanosheets with different Vo concentrations are fabricated to evaluate the influence of defects on the HER process. Unexpectedly, while the generated oxygen vacancies contribute to the enhanced HER performance, higher Vo concentrations beyond a saturation value result in a significant drop in HER activity. By tunning the Vo concentration in the Bi2O3 nanosheets via adjusting the treatment time, the Bi2O3 catalyst with an optimized oxygen vacancy concentration and detectable charge carrier concentration of 1.52 × 1024 cm−3 demonstrates enhanced HER performance with an overpotential of 174.2 mV to reach 10 mA cm−2, a Tafel slope of 80 mV dec−1, and an exchange current density of 316 mA cm−2 in an alkaline solution, which approaches the top-tier activity among Bi-based HER electrocatalysts. Density-functional theory calculations confirm the preferred adsorption of H* onto Bi2O3 as a function of oxygen chemical potential (∆μO) and oxygen partial potential (PO2) and reveal that high Vo concentrations result in excessive stability of adsorbed hydrogen and hence the inferior HER activity. This study reveals the oxygen vacancy concentration-HER catalytic activity relationship and provides insights into activating catalytically inert materials into highly efficient electrocatalysts.

The importance of discovering the true catalytically active species involved in photocatalytic systems allows for a better and more general understanding of photocatalytic processes, which eventually may help to improve their efficiency. Bi 2 O 3 has been used as a heterogeneous photocatalyst and is able to catalyze several synthetically important visible-light-driven organic transformations. However, insight into the operative catalyst involved in the photocatalytic process is hitherto missing. Herein, we show through a combination of theoretical and experimental studies that the perceived heterogeneous photocatalysis with Bi 2 O 3 in the presence of alkyl bromides involves a homogeneous Bi n Br m species, which is the true photocatalyst operative in the reaction. Hence, Bi 2 O 3 can be regarded as a precatalyst which is slowly converted in an active homogeneous photocatalyst. This work can also be of importance to mechanistic studies involving other semiconductor-based photocatalytic processes. The identification of true catalytically active species allows for a better understanding of a catalytic process and its potential improvement. Here, the authors report that the perceived heterogeneous photocatalysis with Bi 2 O 3 in the presence of alkyl bromides involves a homogeneous Bi n Br m species as the true photocatalyst.

Metal/oxide interface is of fundamental significance to heterogeneous catalysis because the seemingly “inert” oxide support can modulate the morphology, atomic and electronic structures of the metal catalyst through the interface. The interfacial effects are well studied over a bulk oxide support but remain elusive for nanometer-sized systems like clusters, arising from the challenges associated with chemical synthesis and structural elucidation of such hybrid clusters. We hereby demonstrate the essential catalytic roles of a nanometer metal/oxide interface constructed by a hybrid Pd/Bi 2 O 3 cluster ensemble, which is fabricated by a facile stepwise photochemical method. The Pd/Bi 2 O 3 cluster, of which the hybrid structure is elucidated by combined electron microscopy and microanalysis, features a small Pd-Pd coordination number and more importantly a Pd-Bi spatial correlation ascribed to the heterografting between Pd and Bi terminated Bi 2 O 3 clusters. The intra-cluster electron transfer towards Pd across the as-formed nanometer metal/oxide interface significantly weakens the ethylene adsorption without compromising the hydrogen activation. As a result, a 91% selectivity of ethylene and 90% conversion of acetylene can be achieved in a front-end hydrogenation process with a temperature as low as 44 °C. Metal/oxide interface is of fundamental significance to heterogeneous catalysis. Here, the authors construct a nanometer Pd/Bi 2 O 3 interface by grafting Pd clusters onto Bi 2 O 3 clusters and demonstrate its essential roles in the low-temperature semi-hydrogenation of acetylene.

This paper provides in-depth experimental validations on the synthesis, optical, thermal, mechanical, and radiation-shielding properties of a novel x Bi 2 O 3 –10MgO–(90- x )B 2 O 3 , where 20 ≤  x  ≤ 40 mol %, glass system. The melt quench process is used to prepare all the samples of this glass system, and the amorphous phase is conformed using an X-ray diffraction test. The structure of all the produced glasses is investigated using differential scanning calorimetry investigations. Moreover, we use Makishima–Mackenzie model to compute the elastic moduli, while the FLUKA simulations are employed to assess the radiation-shielding properties of our glass system. Finally, we compared the obtained results of our new glass system with those of standard and previously published glass systems. The obtained results indicated that the crystallization resistance and mechanical qualities of the glass were enhanced as Bi 2 O 3 content increased. Moreover, the linear attenuation factors for the prepare glasses were maximum at 0.1 MeV with the values of 0.1838 cm −1 , 0.1946 cm −1 , 0.2050 cm −1 , 0.2149 cm −1 and 0.2220 cm −1 as Bi 2 O 3 content increased from 20 to 40 mol %, respectively. Generally, our prepared glasses show promising properties for optical and radiation applications, especially in medical facilities.

Energy absorption buildup factor (EABF) and exposure buildup factor (EBF) of bismuth borate glass systems in structure (75– x ) B 2 O 3 – x Bi 2 O 3 – 10 Na 2 O – 10 CaO – 5 Al 2 O 3 ( 0 ≤ x ≤ 25 mol % ) have been investigated for photon energy region between 0.015 and 15 MeV and for penetration depths of 1–40 mfp. Five parameters (G–P) fitting method has been carried out for computations procedure. The calculated values of EABF and EBF have been observed to be dependent on photon energy, penetration depths and on the concentration of Bi 2 O 3 mol% in the glass sample. It has been found that BOB25 glass offers better gamma-ray shielding than other samples. In addition, the values of EABF and EBF have been compared and significant differences up to 8 % have been noted in intermediate energy region.

Electrostriction is a property of dielectric materials whereby an applied electric field induces a mechanical deformation proportional to the square of that field. The magnitude of the effect is usually minuscule (<10 –19  m 2  V –2 for simple oxides). However, symmetry-breaking phenomena at the interfaces can offer an efficient strategy for the design of new properties 1 , 2 . Here we report an engineered electrostrictive effect via the epitaxial deposition of alternating layers of Gd 2 O 3 -doped CeO 2 and Er 2 O 3 -stabilized δ-Bi 2 O 3 with atomically controlled interfaces on NdGaO 3 substrates. The value of the electrostriction coefficient achieved is 2.38 × 10 –14  m 2  V –2 , exceeding the best known relaxor ferroelectrics by three orders of magnitude. Our theoretical calculations indicate that this greatly enhanced electrostriction arises from coherent strain imparted by interfacial lattice discontinuity. These artificial heterostructures open a new avenue for the design and manipulation of electrostrictive materials and devices for nano/micro actuation and cutting-edge sensors. A system consisting of alternating thin films of two dielectrics is used to produce greatly enhanced electrostriction derived from coherent strain imparted by interfacial lattice discontinuity.