Cu-based catalysts are widely employed for CO or CO2 hydrogenation into methanol. However, their catalytic performance highly depends on supports, and the real evolution of Cu species is still cove...

Stabilizing Cu+ in Cu/SiO2 Catalysts with a Shattuckite-Like Structure Boosts CO2 Hydrogenation into Methanol

Construction of an Ultrathin S-Scheme Heterojunction Based on Few-Layer g-C3N4 and Monolayer Ti3C2Tx MXene for Photocatalytic CO2 Reduction

Solar energy conversion is one of the most versatile approaches for sustainable energy demands. The fundamental limitations for photocatalysis remain light absorption, charge separation, and photoc ...

Defect Engineering of Photocatalysts for Solar Energy Conversion

Ultrasound-assisted synthesis of mixed calcium magnesium oxide (CaMgO2) nanoflakes for photocatalytic degradation of methylene blue.

Efficient separation of electron-hole pairs is vitally crucial to enhancing the analytical performance of paper-based photoelectrochemical (PEC) bioanalysis. Herein, a simple but effective strategy is developed to modulate the effective separation of photogenerated electrons and holes via introducing a polar charge carriers-created (PCC) electric field induced by a classical perovskite ferroelectric BaTiO3 (BTO). By inserting it between the n-type WO3 nanoflakes and p-type Cu2O (WO3 nanoflakes/BTO/Cu2O), the photoelectrode is endowed with a renewable PCC electric field, as a sustaining driving force, to guarantee the realization of directional separation of charge carrier (DSCC) strategy in PEC bioanalysis. The enduring PCC electric field can attract the electrons of Cu2O and holes of WO3, respectively, thereby regulating the directional migration of charge carriers and achieving an enhanced PEC photocurrent for the ultrasensitive quantification based on the highly efficient separation of electron-hole pairs. Consequently, with respect to WO3 nanoflakes/Cu2O and WO3 nanoflakes photoelectrode, the polarized WO3 nanoflakes/BTO/Cu2O photoelectrode exhibits 1.7 and 10.9 times higher photocurrent density, respectively. Benefiting from this, the prominent photocurrent density is obtained which is extremely beneficial for enhancing the sensitivity of PEC bioanalysis. Ultimately, the ultrasensitive detection of model prostate specific antigen (PSA) is realized and presents a linear range of 0.1 pg/mL-50 ng/mL with the detection limitation of 0.036 pg/mL. This work provides the basis for understanding the role of the polarized electric field induced by ferroelectric in tuning the charge separation as well as insights on strategies for constructing high-performance paper-based PEC bioanalysis.

Ultrasensitive Paper-Based Photoelectrochemical Sensing Platform Enabled by the Polar Charge Carriers-Created Electric Field.

In this work, CuO-TiO2 nanoparticles with different CuO mass contents of 2%, 8%, 12%, and 20% are synthesized by flame spray pyrolysis (FSP) method and applied to catalytic combustion of lean CO. The nano-catalyst is characterized by N2-physisorption isotherms, X-ray diffraction (XRD), transmission electron microscopy (TEM), H2-TPR (temperature-programmed reduction) and X-ray photoelectron spectroscopy (XPS). All the catalysts possess a high specific surface area, of which the CuO-TiO2 nanoparticles with 2 wt.% Cu (2CT) is as high as 98 m2/g, and exhibits a spherical structure with a diameter of 15–20 nm. Compared with other methods, the FSP method can significantly improve the loading of CuO without producing large crystalline CuO particles on the catalyst surface. Interestingly, the addition of CuO will essentially change the lattice structure of TiO2 for all catalysts, including its crystal spacing and XRD diffraction angle. Copper cations are embedded in TiO2 lattice to promote the transformation from anatase to rutile by producing oxygen defect at high flame temperature. The interaction between CuO and TiO2 has significant influence on its physicochemical properties. A lower onset reduction temperature on the sample with higher CuO loading is obtained due to the hydrogen spillover effect in H2-TPR test. Moreover, the loaded CuO increases the content of more stable rutile phase in the materials, so that it reduces the strong metal-support interaction (SMSI) effect of CuO and anatase phase to improve the properties of CO catalytic combustion. The synthesized CuO-TiO2 nanoparticles can achieve complete combustion conversion of lean CO at lower temperature of 120°C.

Flame spray pyrolysis synthesized CuO-TiO2 nanoparticles for catalytic combustion of lean CO

Noble metal-free hybrid photocatalysts have recently been extensively studied for their applications in the environment and energy field. However, rational design over these photocatalysts is still a challenging task because the detailed mechanism of multi-component catalysts is not well understood yet. Here, we highlight a state-of-the-art approach, one-step flame spray pyrolysis (FSP), for preparing high-efficiency hybrid CuOx/TiO2 photocatalysts, where simultaneous control over lattice doping and nanocluster modification of Cu species on a TiO2 support is achieved. Effective engineering of Cu valence is achieved, where the surface Cuþ content varies from 15% to as high as 100%. Meanwhile, a high percentage (70–80 mol%) of TiO2 photocatalytic active phase (anatase) is also maintained in the flame-made catalysts. A dramatic enhancement in photocatalytic H2 evolution efficiency of the hybrid catalyst is attained. The maximum photocatalytic H2 evolution rate of the hybrid CuOx/TiO2 catalyst under Xe lamp in a methanol aqueous solution can reach as high as 112.6mmol h , which is 22.1 times higher than that of commercial P25 TiO2. Mechanism investigation via density functional theory calculation and photoluminescence spectra validates that the bulk defect levels and surface-deposited CuOx nanoclusters play key roles in charge separation and extending spectral response.

Simultaneous Control over Lattice Doping and Nanocluster Modification of a Hybrid CuOx/TiO2 Photocatalyst during Flame Synthesis for Enhancing Hydrogen Evolution

Freestanding Silicon Nanowires Mesh for Efficient Electricity Generation from Evaporation-Induced Water Capillary Flow

Integrating Hydrovoltaic Device with Triboelectric Nanogenerator to Achieve Simultaneous Energy Harvesting from Water Droplet and Vapor

Delay generated by digital control will inevitably lead to negative damping of Modular Multilevel Converter (MMC), which also has significant impacts on the high-frequency stability of the integrated system. Controller parameter optimization is an effectively method for MMC impedance optimization and high-frequency resonance suppression. This paper firstly extends the sequence impedance model of MMC by considering delay effects, and analyzes the high-frequency impedance characteristics as well as the stability of the MMC integrated system. Then, the effect of delay on the frequency range of MMC shows negative damping can be analyzed quantitatively by a vector diagram. Based on the quantified frequency range, the boundary of controller parameters can be derived. Finally, an MMC impedance optimization method that traversal all the values within the derived parameter boundaries to obtain the optimal controller parameters that maximize the phase margin of the system.

Xin Chen

Papers

Flame spray pyrolysis synthesized CuO-TiO2 nanoparticles for catalytic combustion of lean CO

Simultaneous Control over Lattice Doping and Nanocluster Modification of a Hybrid CuOx/TiO2 Photocatalyst during Flame Synthesis for Enhancing Hydrogen Evolution

Freestanding Silicon Nanowires Mesh for Efficient Electricity Generation from Evaporation-Induced Water Capillary Flow

Integrating Hydrovoltaic Device with Triboelectric Nanogenerator to Achieve Simultaneous Energy Harvesting from Water Droplet and Vapor

High-Frequency Stability Analysis and Impedance Optimization for an MMC-HVDC Integrated System Considering Delay Effects