Modulating the electronic structure of VS2via Ru decoration for an efficient pH-universal electrocatalytic hydrogen evolution reaction.

High-efficiency water electrolysis over a broad pH range is desirable but challenging. Herein, Ru-decorated VS2 on carbon cloth (Ru-VS2/CC) has been in situ synthesized, which features the regulated electronic structure of VS2 by introducing Ru. It is remarkable that the optimal Ru-VS2/CC displays excellent electrocatalytic hydrogen evolution activity with overpotentials of 89 and 87 mV at -10 mA cm-2 in 0.5 M H2SO4 and 1.0 M KOH, respectively. Theoretical calculations and electrocatalytic measurements have demonstrated that introducing Ru induces an enhanced charge density around the Fermi level, facilitating charge transfer and speeding up the electrocatalytic HER kinetics. The Gibbs free energy of the hydrogen intermediate (ΔGH*) of Ru-VS2/CC (0.23 eV) is much closer to zero than that of pure VS2 (0.51 eV) and Ru (-0.37 eV), demonstrating an easier hydrogen adsorption and desorption process for Ru-VS2/CC. The more favorable ΔGH*, differential charge density and the d-band center endow Ru-VS2 with enhanced intrinsic electrocatalytic activity. This study presents a feasible strategy for enhancing electrocatalytic HER activity by the regulation of the electronic structure and the rational integration of dual active components.

Interfacial Interaction in NiFe LDH/NiS2/VS2 for Enhanced Electrocatalytic Water Splitting.

A bifunctional electrocatalyst with high efficiency and low costs for overall water splitting is critical to achieving a green hydrogen economy and coping with the energy crisis. However, developing robust electrocatalysts still faces huge challenges, owing to unsatisfactory electron transfer and inherent activity. Herein, NiFe LDH/NiS2/VS2 heterojunctions have been designed as freestanding bifunctional electrocatalysts to split water, exhibiting enhanced electron transfer and abundant catalytic sites. The optimum NiFe LDH/NiS2/VS2 electrocatalyst exhibits a small overpotential of 380 mV at 10 mA cm-2 for overall water splitting and superior electrocatalytic performance in both hydrogen and oxygen evolution reactions (HER/OER). Specifically, the electrocatalyst requires overpotentials of 76 and 286 mV at 10 mA cm-2 for HER and OER, respectively, in alkaline electrolytes, which originate from the synergistic interaction among the facilitated electron transfer and increasingly exposed active sites due to the modulation of interfaces and construction of heterojunctions.

Interface engineering of 0D/2D Cu2O/BiOBr Z-scheme heterojunction for efficient degradation of sulfamethoxazole: Mechanism, degradation pathway, and DFT calculation.

Constructed heterojunction has been considered an efficient strategy to enhance the migration and transfer of photoinduced charge carriers. Herein, a Z-scheme Cu2O/BiOBr heterojunction with 0D/2D structure was fabricated by microwave hydrothermal method. It was found that the optimal composites photocatalyst showed excellent activity for sulfamethoxazole (SMZ) illumination, and the removal rate reached 90.7%, which was higher than pristine Cu2O (53.0%) and BiOBr (60.0%). Subsequently, the operational parameters such as catalyst dosage, concentrations of pollutants, and pH of solution were investigated. According to the ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRs), Mott-Schottky curve, and density functional theory (DFT) analysis, the Z-scheme degradation mechanism of Cu2O/BiOBr heterostructure was proposed. Among them, the interface structure of 0-dimensions/2-dimensions (0D/2D) can significantly increase the number of heterojunctions in the composite catalyst, and Z-scheme heterostructures can accelerate the generation and migration of photoinduced charge carriers, which has a facilitation effect on improving the decomposition activity of the photocatalyst. Moreover, three possible pathways for SMZ degradation were inferred. This study provides a promising strategy for constructing novel heterojunctions with high photocatalytic performance.

[Adsorption of Iopamidol by NaHCO3-activated Buckwheat Biochar].

NaHCO3-activated buckwheat biochar was studied, and an optimal biochar of 0.25N-BC [m(NaHCO3):m(buckwheat bark)=0.25:1]was selected. SEM, BET, XRD, Raman, FTIR, and XPS methods were applied to analyze the effects of NaHCO3 on the physicochemical properties of buckwheat biochar. The adsorption properties and mechanism of NaHCO3-activated buckwheat biochar for iopamidol(IPM), a nonionic iodol X-ray contrast agent, were also investigated. The results showed that compared with buckwheat skin biochar(BC), NaHCO3-activated biochar had higher structural defects(surface area and pore volume increased, respectively, from 480.40 m2·g-1 and 0.29 cm3·g-1 to 572.83 m2·g-1 and 0.40 cm3·g-1, with ID/IG being 1.22 times that of BC), the carbon and oxygen functional groups on the BC surface changed significantly, and the polarity increased [(N+O)/C from 0.15 to 0.24]. The maximum adsorption capacity of 0.25N-BC for IPM was 74.94 mg·g-1, which was 9.51 times that of BC(7.88 mg·g-1). The pseudo-second-order adsorption kinetics and Langmuir and Freundlich isotherm models could well fit the adsorption of 0.25N-BC for IPM. The adsorption processes were mainly chemical, monolayer, and heterogeneous multilayer adsorption. Pore filling, hydrogen bonding, π-π, and n-π interactions were the main mechanisms of 0.25N-BC adsorption for IPM. Comparing the activated buckwheat biochar by different bases [KOH, Na2CO3, NaHCO3, KHCO3, and Ca(HCO3)2], 0.25N-BC exhibited high adsorption capability and short equilibrium time and could effectively remove the IPM residue in the actual water(secondary sedimentation tank effluent and lake). The removal rate of IPM remained at 74.91% after three adsorption-desorption cycles. The results showed that NaHCO3-activated buckwheat biochar was a green, effective, and sustainable adsorbent for the removal of iodine-containing organic matter.

Preparation and Photoelectric Properties of Pr-Doped p-Cu2O Thin Films Photocatalyst Based on Energy Band Structure Regulation.

A Pr-doped p-Cu2O thin film was prepared on indium tin oxide conductive glass by electrochemical deposition; the effect of Pr doping on the structure, morphology, and physicochemical properties of p-Cu2O was investigated. The results show that with the increase in Pr doping amount, the particle size of p-Cu2O increases, the absorption boundary redshifts, and the band-gap width decreases. Pr doping increases the flat band potential and carrier concentration of p-Cu2O; when the doping amount is 1.2 mM, the carrier concentration reaches 1.14 × 1024 cm-3. Compared with pure p-Cu2O, the charge transfer resistance of Pr-doped p-Cu2O decreases and the photocurrent and open circuit voltage increase, indicating that the carrier transfer rate is accelerated, and the separation efficiency of photogenerated electrons and holes is effectively improved. The result of a norfloxacin photocatalytic degradation experiment showed that the degradation rate of norfloxacin increased from 52.3% to 76.2% and Pr doping effectively improved the photocatalytic performance of p-Cu2O. The main reasons for enhancing the photocatalytic performance are that the band gap of Pr-doped p-Cu2O decreases, the Fermi level of Cu2O is closer to the valence band position, the hole concentration near the valence band, and the oxidation capacity increases, and more h+ oxidize norfloxacin molecules. In addition, the Pr in Pr-Cu2O acts as a conductor to guide electrons on the guide band to the crystal surface, which increases the contact between photogenerated electrons and dissolved oxygen, which is conducive to the formation of the active species ·O2- and can effectively reduce the recombination of photogenerated carriers. In the process of photocatalytic degradation of norfloxacin, the main active species are ·O2-, ·OH, and h+, which play auxiliary roles. TOC tests show that the norfloxacin molecules can be effectively degraded into small molecule organic matter, CO2, and H2O in the presence of Pr-doped p-Cu2O.

Construction of SrTiO3-BiOCl composite catalyst via facial microwave hydrothermal for highly efficient photocatalytic activity towards organic compounds degradation.

This work mainly focuses on the preparation and performance study of SrTiO3-BiOCl composite photocatalysis. The SrTiO3-BiOCl photocatalysts are prepared via the facial microwave hydrothermal method. XRD, UV-vis DRS, SEM, TEM, XPS, N2 adsorption and desorption isothermal experiment, FT-IR, and PL are applied to characterize the prepared samples. The spherical particles of SrTiO3 grow on the flaky BiOCl, and the crystal size is uniform and evenly disperses on the BiOCl. The catalytic performance of the samples was evaluated over the degradation rates of methylene blue(MB). Typically, the clearance rates of MB reached to 99.65% over SrTiO3-BiOCl-50% under visible light, which was much higher than that of SrTiO3 and BiOCl (55.86%, 79.79%, respectively). The active species capturing experiments and ESR showed that the holes (h+) and ·OH are playing the main roles in the degradation process.

Preparation and performance of Cu2O/TiO2 nanocomposite thin film and photocatalytic degradation of Rhodamine B.

A constant current electrodeposition approach was employed to prepare Cu2O/TiO2 nanocomposite thin film. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), Raman, ultraviolet visible light spectrophotometer (UV-Vis), and photoluminescence (PL) measurements were used to characterize and analyze the thin film microstructure, surface morphology, and photoelectric properties. The effect of annealing treatment on the thin film properties is discussed. The response surface methodology (RSM) was employed to optimize the Rhodamine B (RhB) photocatalytic degradation by thin films, and the quadratic multinomial mathematical model was established. The photocatalytic degradation process of RhB was also studied. The results indicate that the prepared Cu2O thin film was of high purity, with a (111) crystal plane preferred orientation. The average particle diameter was approximately 100-200 nm, and the absorbing boundary was approximately 600 nm. After annealing treatment, the absorbing boundary and open-circuit voltage increased, and Cu2O thin film exhibited an obvious absorbance response in the visible-light range. The established model has better fitness and higher reliability, and the R2 value of established quadratic model is 0.9818. The optimal degradation conditions were obtained by RSM. Under optimum conditions, the RhB degradation rate could reach 98.4% in 3 h and the total organic carbon (TOC) removal rate was 48.2%. Recycling results reveal that RhB degradation rate can still reach 94.5% after eight cycles.

Ultraviolet-assisted direct patterning and low-temperature formation of flexible ZrO2 resistive switching arrays on PET/ITO substrates.

We demonstrate a low-cost and facile photochemical solution method to prepare the ZrO2 resistive switching arrays as memristive units on flexible PET/ITO substrates. ZrO2 solution sensitive to UV light of 337 nm was synthesized using zirconium n-butyl alcohol as the precursor, and benzoylacetone as the complexing agent. After the dip-coated ZrO2 gel films were irradiated through a mask under the UV lamp (with wavelength of 325-365 nm) at room temperature and rinsed in ethanol, the ZrO2 gel arrays were obtained on PET/ITO substrates. Subsequently, the ZrO2 gel arrays were irradiated by deep UV light of 254 and 185 nm at 150 °C, resulting in the amorphous ZrO2 memristive micro-arrays. The ZrO2 units on flexible PET/ITO substrates exhibited excellent memristive properties. A high ratio of 104 of on-state and off-state resistance was obtained. The resistive switching behavior of the flexible device remained stable after being bent for 103 times. The device showed stable flexibility up to a minimum bending diameter of 1.25 cm.